19774894729

Committed 28 Nov 2025 10:22PM UTC coverage: 59.711% (-0.6%) from 60.346%

Build # 19774894729

Build Type

push

github

Committed by

fasterthanlime

Commit Message

Add DynamicValue support for deserializing into facet_value::Value

This adds support for deserializing JSON (and potentially other formats)
into facet_value::Value without format crates needing to depend on facet-value.

Key changes:
- Add Def::DynamicValue variant with vtable for building dynamic values
- Implement Facet trait for Value in facet-value
- Extend Partial to handle DynamicValue scalars via set_into_dynamic_value
- Add deserialize_dynamic_value handler in facet-json

Currently supports scalar values (null, bool, numbers, strings).
Arrays and objects are stubbed out with TODO errors.

Run Details

451 of 922 new or added lines in 20 files covered. (48.92%)

29 existing lines in 3 files now uncovered.

16657 of 27896 relevant lines covered (59.71%)

153.76 hits per line

Source File
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77.95

/facet-reflect/src/partial/partial_api/misc.rs

use super::*;

////////////////////////////////////////////////////////////////////////////////////////////////////
// Misc.
////////////////////////////////////////////////////////////////////////////////////////////////////
impl<'facet> Partial<'facet> {
    /// Returns the current frame count (depth of nesting)
    ///
    /// The initial frame count is 1 — `begin_field` would push a new frame,
    /// bringing it to 2, then `end` would bring it back to `1`.
    ///
    /// This is an implementation detail of `Partial`, kinda, but deserializers
    /// might use this for debug assertions, to make sure the state is what
    /// they think it is.
    #[inline]
    pub fn frame_count(&self) -> usize {
        self.frames().len()
    }

    /// Returns the shape of the current frame.
    #[inline]
    pub fn shape(&self) -> &'static Shape {
        self.frames()
            .last()
            .expect("Partial always has at least one frame")
            .shape
    }

    /// Returns the current deferred resolution, if in deferred mode.
    #[inline]
    pub fn deferred_resolution(&self) -> Option<&Resolution> {
        self.resolution()
    }

    /// Returns the current path in deferred mode as a slice (for debugging/tracing).
    #[inline]
    pub fn current_path_slice(&self) -> Option<&[&'static str]> {
        self.current_path().map(|p| p.as_slice())
    }

    /// Enables deferred materialization mode with the given Resolution.
    ///
    /// When deferred mode is enabled:
    /// - `end()` stores frames instead of validating them
    /// - Re-entering a path restores the stored frame with its state intact
    /// - `finish_deferred()` performs final validation and materialization
    ///
    /// This allows deserializers to handle interleaved fields (e.g., TOML dotted
    /// keys, flattened structs) where nested fields aren't contiguous in the input.
    ///
    /// # Use Cases
    ///
    /// - TOML dotted keys: `inner.x = 1` followed by `count = 2` then `inner.y = 3`
    /// - Flattened structs where nested fields appear at the parent level
    /// - Any format where field order doesn't match struct nesting
    ///
    /// # Errors
    ///
    /// Returns an error if already in deferred mode.
    #[inline]
    pub fn begin_deferred(&mut self, resolution: Resolution) -> Result<&mut Self, ReflectError> {
        // Cannot enable deferred mode if already in deferred mode
        if self.is_deferred() {
            return Err(ReflectError::InvariantViolation {
                invariant: "begin_deferred() called but already in deferred mode",
            });
        }

        // Take the stack out of Strict mode and wrap in Deferred mode
        let FrameMode::Strict { stack } = core::mem::replace(
            &mut self.mode,
            FrameMode::Strict { stack: Vec::new() }, // temporary placeholder
        ) else {
            unreachable!("just checked we're not in deferred mode");
        };

        let start_depth = stack.len();
        self.mode = FrameMode::Deferred {
            stack,
            resolution,
            start_depth,
            current_path: Vec::new(),
            stored_frames: BTreeMap::new(),
        };
        Ok(self)
    }

    /// Finishes deferred mode: validates all stored frames and finalizes.
    ///
    /// This method:
    /// 1. Validates that all stored frames are fully initialized
    /// 2. Processes frames from deepest to shallowest, updating parent ISets
    /// 3. Validates the root frame
    ///
    /// # Errors
    ///
    /// Returns an error if any required fields are missing or if the partial is
    /// not in deferred mode.
    pub fn finish_deferred(&mut self) -> Result<&mut Self, ReflectError> {
        // Check if we're in deferred mode first, before extracting state
        if !self.is_deferred() {
            return Err(ReflectError::InvariantViolation {
                invariant: "finish_deferred() called but deferred mode is not enabled",
            });
        }

        // Extract deferred state, transitioning back to Strict mode
        let FrameMode::Deferred {
            stack,
            start_depth,
            mut stored_frames,
            ..
        } = core::mem::replace(&mut self.mode, FrameMode::Strict { stack: Vec::new() })
        else {
            unreachable!("just checked is_deferred()");
        };

        // Restore the stack to self.mode
        self.mode = FrameMode::Strict { stack };

        // Sort paths by depth (deepest first) so we process children before parents
        let mut paths: Vec<_> = stored_frames.keys().cloned().collect();
        paths.sort_by_key(|b| core::cmp::Reverse(b.len()));

        trace!(
            "finish_deferred: Processing {} stored frames in order: {:?}",
            paths.len(),
            paths
        );

        // Process each stored frame from deepest to shallowest
        for path in paths {
            let mut frame = stored_frames.remove(&path).unwrap();

            trace!(
                "finish_deferred: Processing frame at {:?}, shape {}, tracker {:?}",
                path,
                frame.shape,
                frame.tracker.kind()
            );

            // Fill in defaults for unset fields that have defaults
            frame.fill_defaults();

            // Validate the frame is fully initialized
            if let Err(e) = frame.require_full_initialization() {
                // With the ownership transfer model:
                // - Parent's iset was cleared when we entered this field
                // - Parent won't drop it, so we must deinit it ourselves
                frame.deinit();

                // Clean up remaining stored frames before returning error.
                // All stored frames have their parent's iset cleared, so we must deinit them.
                // Note: we must call deinit() even for partially initialized frames, since
                // deinit() properly handles partial initialization via the tracker's iset.
                for (_, mut remaining_frame) in stored_frames {
                    remaining_frame.deinit();
                }
                return Err(e);
            }

            // Update parent's ISet to mark this field as initialized.
            // The parent could be:
            // 1. On the frames stack (if path.len() == 1, parent is at start_depth - 1)
            // 2. On the frames stack (if parent was pushed but never ended)
            // 3. In stored_frames (if parent was ended during deferred mode)
            if let Some(field_name) = path.last() {
                let parent_path: Vec<_> = path[..path.len() - 1].to_vec();

                if parent_path.is_empty() {
                    // Parent is the frame that was current when deferred mode started.
                    // It's at index (start_depth - 1) because deferred mode stores frames
                    // relative to the position at start_depth.
                    let parent_index = start_depth.saturating_sub(1);
                    if let Some(root_frame) = self.frames_mut().get_mut(parent_index) {
                        Self::mark_field_initialized(root_frame, field_name);
                    }
                } else {
                    // Try stored_frames first
                    if let Some(parent_frame) = stored_frames.get_mut(&parent_path) {
                        Self::mark_field_initialized(parent_frame, field_name);
                    } else {
                        // Parent might still be on the frames stack (never ended).
                        // The frame at index (start_depth + parent_path.len() - 1) should be the parent.
                        let parent_frame_index = start_depth + parent_path.len() - 1;
                        if let Some(parent_frame) = self.frames_mut().get_mut(parent_frame_index) {
                            Self::mark_field_initialized(parent_frame, field_name);
                        }
                    }
                }
            }

            // Frame is validated and parent is updated - frame is no longer needed
            // (The actual data is already in place in memory, pointed to by parent)
            drop(frame);
        }

        // Fill defaults and validate the root frame is fully initialized
        if let Some(frame) = self.frames_mut().last_mut() {
            frame.fill_defaults();
            frame.require_full_initialization()?;
        }

        Ok(self)
    }

    /// Mark a field as initialized in a frame's tracker
    fn mark_field_initialized(frame: &mut Frame, field_name: &str) {
        if let Some(idx) = Self::find_field_index(frame, field_name) {
            match &mut frame.tracker {
                Tracker::Struct { iset, .. } => {
                    iset.set(idx);
                }
                Tracker::Enum { data, .. } => {
                    data.set(idx);
                }
                Tracker::Array { iset, .. } => {
                    iset.set(idx);
                }
                _ => {}
            }
        }
    }

    /// Find the field index for a given field name in a frame
    fn find_field_index(frame: &Frame, field_name: &str) -> Option<usize> {
        match frame.shape.ty {
            Type::User(UserType::Struct(struct_type)) => {
                struct_type.fields.iter().position(|f| f.name == field_name)
            }
            Type::User(UserType::Enum(_)) => {
                if let Tracker::Enum { variant, .. } = &frame.tracker {
                    variant
                        .data
                        .fields
                        .iter()
                        .position(|f| f.name == field_name)
                } else {
                    None
                }
            }
            _ => None,
        }
    }

    /// Pops the current frame off the stack, indicating we're done initializing the current field
    pub fn end(&mut self) -> Result<&mut Self, ReflectError> {
        if let Some(_frame) = self.frames().last() {
            crate::trace!(
                "end() called: shape={}, tracker={:?}, is_init={}",
                _frame.shape,
                _frame.tracker.kind(),
                _frame.is_init
            );
        }
        self.require_active()?;

        // Special handling for SmartPointerSlice - convert builder to Arc
        if self.frames().len() == 1 {
            let frames = self.frames_mut();
            if let Tracker::SmartPointerSlice {
                vtable,
                building_item,
            } = &frames[0].tracker
            {
                if *building_item {
                    return Err(ReflectError::OperationFailed {
                        shape: frames[0].shape,
                        operation: "still building an item, finish it first",
                    });
                }

                // Convert the builder to Arc<[T]>
                let vtable = *vtable;
                let builder_ptr = unsafe { frames[0].data.assume_init() };
                let arc_ptr = unsafe { (vtable.convert_fn)(builder_ptr) };

                // Update the frame to store the Arc
                frames[0].data = PtrUninit::new(unsafe {
                    NonNull::new_unchecked(arc_ptr.as_byte_ptr() as *mut u8)
                });
                frames[0].tracker = Tracker::Scalar;
                frames[0].is_init = true;
                // The builder memory has been consumed by convert_fn, so we no longer own it
                frames[0].ownership = FrameOwnership::ManagedElsewhere;

                return Ok(self);
            }
        }

        if self.frames().len() <= 1 {
            // Never pop the last/root frame.
            return Err(ReflectError::InvariantViolation {
                invariant: "Partial::end() called with only one frame on the stack",
            });
        }

        // In deferred mode, cannot pop below the start depth
        if let Some(start_depth) = self.start_depth() {
            if self.frames().len() <= start_depth {
                return Err(ReflectError::InvariantViolation {
                    invariant: "Partial::end() called but would pop below deferred start depth",
                });
            }
        }

        // Require that the top frame is fully initialized before popping.
        // Skip this check in deferred mode - validation happens in finish_deferred().
        // EXCEPT for collection items (map, list, set, option) which must be fully
        // initialized before insertion/completion.
        let requires_full_init = if !self.is_deferred() {
            true
        } else {
            // In deferred mode, check if parent is a collection that requires
            // fully initialized items (map, list, set, option)
            if self.frames().len() >= 2 {
                let frame_len = self.frames().len();
                let parent_frame = &self.frames()[frame_len - 2];
                matches!(
                    parent_frame.tracker,
                    Tracker::Map { .. }
                        | Tracker::List { .. }
                        | Tracker::Set { .. }
                        | Tracker::Option { .. }
                        | Tracker::DynamicValue {
                            state: DynamicValueState::Array { .. }
                        }
                )
            } else {
                false
            }
        };

        if requires_full_init {
            let frame = self.frames().last().unwrap();
            crate::trace!(
                "end(): Checking full init for {}, tracker={:?}, is_init={}",
                frame.shape,
                frame.tracker.kind(),
                frame.is_init
            );
            let result = frame.require_full_initialization();
            crate::trace!(
                "end(): require_full_initialization result: {:?}",
                result.is_ok()
            );
            result?
        }

        // Pop the frame and save its data pointer for SmartPointer handling
        let mut popped_frame = self.frames_mut().pop().unwrap();

        // In deferred mode, store the frame for potential re-entry and skip
        // the normal parent-updating logic. The frame will be finalized later
        // in finish_deferred().
        //
        // We only store if the path depth matches the frame depth, meaning we're
        // ending a tracked struct/enum field, not something like begin_some()
        // or a field inside a collection item.
        if let FrameMode::Deferred {
            stack,
            start_depth,
            current_path,
            stored_frames,
            ..
        } = &mut self.mode
        {
            // Path depth should match the relative frame depth for a tracked field.
            // After popping: frames.len() - start_depth + 1 should equal path.len()
            // for fields entered via begin_field (not begin_some/begin_inner).
            let relative_depth = stack.len() - *start_depth + 1;
            let is_tracked_field = !current_path.is_empty() && current_path.len() == relative_depth;

            if is_tracked_field {
                trace!(
                    "end(): Storing frame for deferred path {:?}, shape {}",
                    current_path, popped_frame.shape
                );

                // Store the frame at the current path
                let path = current_path.clone();
                stored_frames.insert(path, popped_frame);

                // Pop from current_path
                current_path.pop();

                // Clear parent's current_child tracking
                if let Some(parent_frame) = stack.last_mut() {
                    parent_frame.tracker.clear_current_child();
                }

                return Ok(self);
            }
        }

        // check if this needs deserialization from a different shape
        if popped_frame.using_custom_deserialization {
            if let Some(deserialize_with) = self
                .parent_field()
                .and_then(|field| field.vtable.deserialize_with)
            {
                let parent_frame = self.frames_mut().last_mut().unwrap();

                trace!(
                    "Detected custom conversion needed from {} to {}",
                    popped_frame.shape, parent_frame.shape
                );

                unsafe {
                    let res = {
                        let inner_value_ptr = popped_frame.data.assume_init().as_const();
                        (deserialize_with)(inner_value_ptr, parent_frame.data)
                    };
                    let popped_frame_shape = popped_frame.shape;

                    // we need to do this before any error handling to avoid leaks
                    popped_frame.deinit();
                    popped_frame.dealloc();
                    let rptr = res.map_err(|message| ReflectError::CustomDeserializationError {
                        message,
                        src_shape: popped_frame_shape,
                        dst_shape: parent_frame.shape,
                    })?;
                    if rptr.as_uninit() != parent_frame.data {
                        return Err(ReflectError::CustomDeserializationError {
                            message: "deserialize_with did not return the expected pointer".into(),
                            src_shape: popped_frame_shape,
                            dst_shape: parent_frame.shape,
                        });
                    }
                    parent_frame.mark_as_init();
                }
                return Ok(self);
            }
        }

        // Update parent frame's tracking when popping from a child
        let parent_frame = self.frames_mut().last_mut().unwrap();

        crate::trace!(
            "end(): Popped {} (tracker {:?}), Parent {} (tracker {:?})",
            popped_frame.shape,
            popped_frame.tracker.kind(),
            parent_frame.shape,
            parent_frame.tracker.kind()
        );

        // Check if we need to do a conversion - this happens when:
        // 1. The parent frame has an inner type that matches the popped frame's shape
        // 2. The parent frame has try_from
        // 3. The parent frame is not yet initialized
        // 4. The parent frame's tracker is Scalar (not Option, SmartPointer, etc.)
        //    This ensures we only do conversion when begin_inner was used, not begin_some
        let needs_conversion = !parent_frame.is_init
            && matches!(parent_frame.tracker, Tracker::Scalar)
            && parent_frame.shape.inner.is_some()
            && parent_frame.shape.inner.unwrap() == popped_frame.shape
            && parent_frame.shape.vtable.try_from.is_some();

        if needs_conversion {
            trace!(
                "Detected implicit conversion needed from {} to {}",
                popped_frame.shape, parent_frame.shape
            );

            // The conversion requires the source frame to be fully initialized
            // (we're about to call assume_init() and pass to try_from)
            if let Err(e) = popped_frame.require_full_initialization() {
                // Deallocate the memory since the frame wasn't fully initialized
                if let FrameOwnership::Owned = popped_frame.ownership {
                    if let Ok(layout) = popped_frame.shape.layout.sized_layout() {
                        if layout.size() > 0 {
                            trace!(
                                "Deallocating uninitialized conversion frame memory: size={}, align={}",
                                layout.size(),
                                layout.align()
                            );
                            unsafe {
                                ::alloc::alloc::dealloc(
                                    popped_frame.data.as_mut_byte_ptr(),
                                    layout,
                                );
                            }
                        }
                    }
                }
                return Err(e);
            }

            // Perform the conversion
            if let Some(try_from_fn) = parent_frame.shape.vtable.try_from {
                let inner_ptr = unsafe { popped_frame.data.assume_init().as_const() };
                let inner_shape = popped_frame.shape;

                trace!("Converting from {} to {}", inner_shape, parent_frame.shape);
                let result = unsafe { try_from_fn(inner_ptr, inner_shape, parent_frame.data) };

                if let Err(e) = result {
                    trace!("Conversion failed: {e:?}");

                    // Deallocate the inner value's memory since conversion failed
                    if let FrameOwnership::Owned = popped_frame.ownership {
                        if let Ok(layout) = popped_frame.shape.layout.sized_layout() {
                            if layout.size() > 0 {
                                trace!(
                                    "Deallocating conversion frame memory after failure: size={}, align={}",
                                    layout.size(),
                                    layout.align()
                                );
                                unsafe {
                                    ::alloc::alloc::dealloc(
                                        popped_frame.data.as_mut_byte_ptr(),
                                        layout,
                                    );
                                }
                            }
                        }
                    }

                    return Err(ReflectError::TryFromError {
                        src_shape: inner_shape,
                        dst_shape: parent_frame.shape,
                        inner: e,
                    });
                }

                trace!("Conversion succeeded, marking parent as initialized");
                parent_frame.is_init = true;

                // Deallocate the inner value's memory since try_from consumed it
                if let FrameOwnership::Owned = popped_frame.ownership {
                    if let Ok(layout) = popped_frame.shape.layout.sized_layout() {
                        if layout.size() > 0 {
                            trace!(
                                "Deallocating conversion frame memory: size={}, align={}",
                                layout.size(),
                                layout.align()
                            );
                            unsafe {
                                ::alloc::alloc::dealloc(
                                    popped_frame.data.as_mut_byte_ptr(),
                                    layout,
                                );
                            }
                        }
                    }
                }

                return Ok(self);
            }
        }

        // For Field-owned frames, reclaim responsibility in parent's tracker
        if let FrameOwnership::Field { field_idx } = popped_frame.ownership {
            match &mut parent_frame.tracker {
                Tracker::Struct {
                    iset,
                    current_child,
                } => {
                    iset.set(field_idx); // Parent reclaims responsibility
                    *current_child = None;
                }
                Tracker::Array {
                    iset,
                    current_child,
                } => {
                    iset.set(field_idx); // Parent reclaims responsibility
                    *current_child = None;
                }
                Tracker::Enum {
                    data,
                    current_child,
                    ..
                } => {
                    data.set(field_idx); // Parent reclaims responsibility
                    *current_child = None;
                }
                _ => {}
            }
            return Ok(self);
        }

        match &mut parent_frame.tracker {
            Tracker::SmartPointer => {
                // We just popped the inner value frame, so now we need to create the smart pointer
                if let Def::Pointer(smart_ptr_def) = parent_frame.shape.def {
                    // The inner value must be fully initialized before we can create the smart pointer
                    if let Err(e) = popped_frame.require_full_initialization() {
                        // Inner value wasn't initialized, deallocate and return error
                        popped_frame.deinit();
                        popped_frame.dealloc();
                        return Err(e);
                    }

                    let Some(new_into_fn) = smart_ptr_def.vtable.new_into_fn else {
                        popped_frame.deinit();
                        popped_frame.dealloc();
                        return Err(ReflectError::OperationFailed {
                            shape: parent_frame.shape,
                            operation: "SmartPointer missing new_into_fn",
                        });
                    };

                    // The child frame contained the inner value
                    let inner_ptr = PtrMut::new(unsafe {
                        NonNull::new_unchecked(popped_frame.data.as_mut_byte_ptr())
                    });

                    // Use new_into_fn to create the Box
                    unsafe {
                        new_into_fn(parent_frame.data, inner_ptr);
                    }

                    // We just moved out of it
                    popped_frame.tracker = Tracker::Scalar;
                    popped_frame.is_init = false;

                    // Deallocate the inner value's memory since new_into_fn moved it
                    popped_frame.dealloc();

                    parent_frame.is_init = true;
                }
            }
            Tracker::List { current_child } if parent_frame.is_init => {
                if *current_child {
                    // We just popped an element frame, now push it to the list
                    if let Def::List(list_def) = parent_frame.shape.def {
                        let Some(push_fn) = list_def.vtable.push else {
                            return Err(ReflectError::OperationFailed {
                                shape: parent_frame.shape,
                                operation: "List missing push function",
                            });
                        };

                        // The child frame contained the element value
                        let element_ptr = PtrMut::new(unsafe {
                            NonNull::new_unchecked(popped_frame.data.as_mut_byte_ptr())
                        });

                        // Use push to add element to the list
                        unsafe {
                            push_fn(
                                PtrMut::new(NonNull::new_unchecked(
                                    parent_frame.data.as_mut_byte_ptr(),
                                )),
                                element_ptr,
                            );
                        }

                        // Push moved out of popped_frame
                        popped_frame.tracker = Tracker::Scalar;
                        popped_frame.is_init = false;
                        popped_frame.dealloc();

                        *current_child = false;
                    }
                }
            }
            Tracker::Map { insert_state } if parent_frame.is_init => {
                match insert_state {
                    MapInsertState::PushingKey { key_ptr, .. } => {
                        // We just popped the key frame - mark key as initialized and transition
                        // to PushingValue state
                        *insert_state = MapInsertState::PushingValue {
                            key_ptr: *key_ptr,
                            value_ptr: None,
                            value_initialized: false,
                        };
                    }
                    MapInsertState::PushingValue {
                        key_ptr, value_ptr, ..
                    } => {
                        // We just popped the value frame, now insert the pair
                        if let (Some(value_ptr), Def::Map(map_def)) =
                            (value_ptr, parent_frame.shape.def)
                        {
                            let insert_fn = map_def.vtable.insert_fn;

                            // Use insert to add key-value pair to the map
                            unsafe {
                                insert_fn(
                                    PtrMut::new(NonNull::new_unchecked(
                                        parent_frame.data.as_mut_byte_ptr(),
                                    )),
                                    PtrMut::new(NonNull::new_unchecked(key_ptr.as_mut_byte_ptr())),
                                    PtrMut::new(NonNull::new_unchecked(
                                        value_ptr.as_mut_byte_ptr(),
                                    )),
                                );
                            }

                            // Note: We don't deallocate the key and value memory here.
                            // The insert function has semantically moved the values into the map,
                            // but we still need to deallocate the temporary buffers.
                            // However, since we don't have frames for them anymore (they were popped),
                            // we need to handle deallocation here.
                            if let Ok(key_shape) = map_def.k().layout.sized_layout() {
                                if key_shape.size() > 0 {
                                    unsafe {
                                        ::alloc::alloc::dealloc(
                                            key_ptr.as_mut_byte_ptr(),
                                            key_shape,
                                        );
                                    }
                                }
                            }
                            if let Ok(value_shape) = map_def.v().layout.sized_layout() {
                                if value_shape.size() > 0 {
                                    unsafe {
                                        ::alloc::alloc::dealloc(
                                            value_ptr.as_mut_byte_ptr(),
                                            value_shape,
                                        );
                                    }
                                }
                            }

                            // Reset to idle state
                            *insert_state = MapInsertState::Idle;
                        }
                    }
                    MapInsertState::Idle => {
                        // Nothing to do
                    }
                }
            }
            Tracker::Set { current_child } if parent_frame.is_init => {
                if *current_child {
                    // We just popped an element frame, now insert it into the set
                    if let Def::Set(set_def) = parent_frame.shape.def {
                        let insert_fn = set_def.vtable.insert_fn;

                        // The child frame contained the element value
                        let element_ptr = PtrMut::new(unsafe {
                            NonNull::new_unchecked(popped_frame.data.as_mut_byte_ptr())
                        });

                        // Use insert to add element to the set
                        unsafe {
                            insert_fn(
                                PtrMut::new(NonNull::new_unchecked(
                                    parent_frame.data.as_mut_byte_ptr(),
                                )),
                                element_ptr,
                            );
                        }

                        // Insert moved out of popped_frame
                        popped_frame.tracker = Tracker::Scalar;
                        popped_frame.is_init = false;
                        popped_frame.dealloc();

                        *current_child = false;
                    }
                }
            }
            Tracker::Option { building_inner } => {
                crate::trace!(
                    "end(): matched Tracker::Option, building_inner={}",
                    *building_inner
                );
                // We just popped the inner value frame for an Option's Some variant
                if *building_inner {
                    if let Def::Option(option_def) = parent_frame.shape.def {
                        // Use the Option vtable to initialize Some(inner_value)
                        let init_some_fn = option_def.vtable.init_some_fn;

                        // The popped frame contains the inner value
                        let inner_value_ptr = unsafe { popped_frame.data.assume_init().as_const() };

                        // Initialize the Option as Some(inner_value)
                        unsafe {
                            init_some_fn(parent_frame.data, inner_value_ptr);
                        }

                        // Deallocate the inner value's memory since init_some_fn moved it
                        if let FrameOwnership::Owned = popped_frame.ownership {
                            if let Ok(layout) = popped_frame.shape.layout.sized_layout() {
                                if layout.size() > 0 {
                                    unsafe {
                                        ::alloc::alloc::dealloc(
                                            popped_frame.data.as_mut_byte_ptr(),
                                            layout,
                                        );
                                    }
                                }
                            }
                        }

                        // Mark that we're no longer building the inner value
                        *building_inner = false;
                        crate::trace!("end(): set building_inner to false");
                        // Mark the Option as initialized
                        parent_frame.is_init = true;
                        crate::trace!("end(): set parent_frame.is_init to true");
                    } else {
                        return Err(ReflectError::OperationFailed {
                            shape: parent_frame.shape,
                            operation: "Option frame without Option definition",
                        });
                    }
                } else {
                    // building_inner is false - the Option was already initialized but
                    // begin_some was called again. The popped frame was not used to
                    // initialize the Option, so we need to clean it up.
                    popped_frame.deinit();
                    if let FrameOwnership::Owned = popped_frame.ownership {
                        if let Ok(layout) = popped_frame.shape.layout.sized_layout() {
                            if layout.size() > 0 {
                                unsafe {
                                    ::alloc::alloc::dealloc(
                                        popped_frame.data.as_mut_byte_ptr(),
                                        layout,
                                    );
                                }
                            }
                        }
                    }
                }
            }
            Tracker::Scalar => {
                // the main case here is: the popped frame was a `String` and the
                // parent frame is an `Arc<str>`, `Box<str>` etc.
                match &parent_frame.shape.def {
                    Def::Pointer(smart_ptr_def) => {
                        let pointee =
                            smart_ptr_def
                                .pointee()
                                .ok_or(ReflectError::InvariantViolation {
                                    invariant: "pointer type doesn't have a pointee",
                                })?;

                        if !pointee.is_shape(str::SHAPE) {
                            return Err(ReflectError::InvariantViolation {
                                invariant: "only T=str is supported when building SmartPointer<T> and T is unsized",
                            });
                        }

                        if !popped_frame.shape.is_shape(String::SHAPE) {
                            return Err(ReflectError::InvariantViolation {
                                invariant: "the popped frame should be String when building a SmartPointer<T>",
                            });
                        }

                        popped_frame.require_full_initialization()?;

                        // if the just-popped frame was a SmartPointerStr, we have some conversion to do:
                        // Special-case: SmartPointer<str> (Box<str>, Arc<str>, Rc<str>) via SmartPointerStr tracker
                        // Here, popped_frame actually contains a value for String that should be moved into the smart pointer.
                        // We convert the String into Box<str>, Arc<str>, or Rc<str> as appropriate and write it to the parent frame.
                        use ::alloc::{rc::Rc, string::String, sync::Arc};
                        let parent_shape = parent_frame.shape;

                        let Some(known) = smart_ptr_def.known else {
                            return Err(ReflectError::OperationFailed {
                                shape: parent_shape,
                                operation: "SmartPointerStr for unknown smart pointer kind",
                            });
                        };

                        parent_frame.deinit();

                        // Interpret the memory as a String, then convert and write.
                        let string_ptr = popped_frame.data.as_mut_byte_ptr() as *mut String;
                        let string_value = unsafe { core::ptr::read(string_ptr) };

                        match known {
                            KnownPointer::Box => {
                                let boxed: Box<str> = string_value.into_boxed_str();
                                unsafe {
                                    core::ptr::write(
                                        parent_frame.data.as_mut_byte_ptr() as *mut Box<str>,
                                        boxed,
                                    );
                                }
                            }
                            KnownPointer::Arc => {
                                let arc: Arc<str> = Arc::from(string_value.into_boxed_str());
                                unsafe {
                                    core::ptr::write(
                                        parent_frame.data.as_mut_byte_ptr() as *mut Arc<str>,
                                        arc,
                                    );
                                }
                            }
                            KnownPointer::Rc => {
                                let rc: Rc<str> = Rc::from(string_value.into_boxed_str());
                                unsafe {
                                    core::ptr::write(
                                        parent_frame.data.as_mut_byte_ptr() as *mut Rc<str>,
                                        rc,
                                    );
                                }
                            }
                            _ => {
                                return Err(ReflectError::OperationFailed {
                                    shape: parent_shape,
                                    operation: "Don't know how to build this pointer type",
                                });
                            }
                        }

                        parent_frame.is_init = true;

                        popped_frame.tracker = Tracker::Scalar;
                        popped_frame.is_init = false;
                        popped_frame.dealloc();
                    }
                    _ => {
                        // This can happen if begin_inner() was called on a type that
                        // has shape.inner but isn't a SmartPointer (e.g., Option).
                        // In this case, we can't complete the conversion, so return error.
                        return Err(ReflectError::OperationFailed {
                            shape: parent_frame.shape,
                            operation: "end() called but parent has Uninit/Init tracker and isn't a SmartPointer",
                        });
                    }
                }
            }
            Tracker::SmartPointerSlice {
                vtable,
                building_item,
            } => {
                if *building_item {
                    // We just popped an element frame, now push it to the slice builder
                    let element_ptr = PtrMut::new(unsafe {
                        NonNull::new_unchecked(popped_frame.data.as_mut_byte_ptr())
                    });

                    // Use the slice builder's push_fn to add the element
                    crate::trace!("Pushing element to slice builder");
                    unsafe {
                        let parent_ptr = parent_frame.data.assume_init();
                        (vtable.push_fn)(parent_ptr, element_ptr);
                    }

                    popped_frame.tracker = Tracker::Scalar;
                    popped_frame.is_init = false;
                    popped_frame.dealloc();

                    if let Tracker::SmartPointerSlice {
                        building_item: bi, ..
                    } = &mut parent_frame.tracker
                    {
                        *bi = false;
                    }
                }
            }
            Tracker::DynamicValue {
                state: DynamicValueState::Array { building_element },
            } => {
                if *building_element {
                    // We just popped an element frame, now push it to the dynamic array
                    if let Def::DynamicValue(dyn_def) = parent_frame.shape.def {
                        // Get mutable pointers - both array and element need PtrMut
                        let array_ptr = unsafe { parent_frame.data.assume_init() };
                        let element_ptr = unsafe { popped_frame.data.assume_init() };

                        // Use push_array_element to add element to the array
                        unsafe {
                            (dyn_def.vtable.push_array_element)(array_ptr, element_ptr);
                        }

                        // Push moved out of popped_frame
                        popped_frame.tracker = Tracker::Scalar;
                        popped_frame.is_init = false;
                        popped_frame.dealloc();

                        *building_element = false;
                    }
                }
            }
            _ => {}
        }

        Ok(self)
    }

    /// Returns a human-readable path representing the current traversal in the builder,
    /// e.g., `RootStruct.fieldName[index].subfield`.
    pub fn path(&self) -> String {
        let mut out = String::new();

        let mut path_components = Vec::new();
        // The stack of enum/struct/sequence names currently in context.
        // Start from root and build upwards.
        for (i, frame) in self.frames().iter().enumerate() {
            match frame.shape.ty {
                Type::User(user_type) => match user_type {
                    UserType::Struct(struct_type) => {
                        // Try to get currently active field index
                        let mut field_str = None;
                        if let Tracker::Struct {
                            current_child: Some(idx),
                            ..
                        } = &frame.tracker
                        {
                            if let Some(field) = struct_type.fields.get(*idx) {
                                field_str = Some(field.name);
                            }
                        }
                        if i == 0 {
                            // Use Display for the root struct shape
                            path_components.push(format!("{}", frame.shape));
                        }
                        if let Some(field_name) = field_str {
                            path_components.push(format!(".{field_name}"));
                        }
                    }
                    UserType::Enum(_enum_type) => {
                        // Try to get currently active variant and field
                        if let Tracker::Enum {
                            variant,
                            current_child,
                            ..
                        } = &frame.tracker
                        {
                            if i == 0 {
                                // Use Display for the root enum shape
                                path_components.push(format!("{}", frame.shape));
                            }
                            path_components.push(format!("::{}", variant.name));
                            if let Some(idx) = *current_child {
                                if let Some(field) = variant.data.fields.get(idx) {
                                    path_components.push(format!(".{}", field.name));
                                }
                            }
                        } else if i == 0 {
                            // just the enum display
                            path_components.push(format!("{}", frame.shape));
                        }
                    }
                    UserType::Union(_union_type) => {
                        path_components.push(format!("{}", frame.shape));
                    }
                    UserType::Opaque => {
                        path_components.push("<opaque>".to_string());
                    }
                },
                Type::Sequence(seq_type) => match seq_type {
                    facet_core::SequenceType::Array(_array_def) => {
                        // Try to show current element index
                        if let Tracker::Array {
                            current_child: Some(idx),
                            ..
                        } = &frame.tracker
                        {
                            path_components.push(format!("[{idx}]"));
                        }
                    }
                    // You can add more for Slice, Vec, etc., if applicable
                    _ => {
                        // just indicate "[]" for sequence
                        path_components.push("[]".to_string());
                    }
                },
                Type::Pointer(_) => {
                    // Indicate deref
                    path_components.push("*".to_string());
                }
                _ => {
                    // No structural path
                }
            }
        }
        // Merge the path_components into a single string
        for component in path_components {
            out.push_str(&component);
        }
        out
    }

    /// Get the field for the parent frame
    pub fn parent_field(&self) -> Option<&Field> {
        self.frames()
            .iter()
            .rev()
            .nth(1)
            .and_then(|f| f.get_field())
    }

    /// Gets the field for the current frame
    pub fn current_field(&self) -> Option<&Field> {
        self.frames().last().and_then(|f| f.get_field())
    }
}

facet-rs / facet / 19774894729

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