go-sql-driver / mysql / 41033624084

86%

push

github

packets: fix inverted unknown collation check (#1832)

The handshake carries a one-byte collation ID, so the `collations` map
only holds IDs below 256. With `charset` set, the collation is applied
after auth by `SET NAMES <charset> COLLATE <collation>`, so newer
collations work there (see #1665). Since #1604, the handshake returns
`unknown collation` only when a charset is set, the opposite of the
comment on that branch. So the #1603 DSN
`charset=utf8mb4&collation=utf8mb4_0900_as_ci` and `Charset("utf8mb4",
"utf8mb4_0900_bin")` still fail with `unknown collation`, while
`collation=utf8mb4_0900_as_ci` alone connects and silently uses
utf8mb4_general_ci.

This flips the condition. With a charset, an unknown collation now sends
the default ID and `SET NAMES` sets the real one. Without a charset, an
unknown collation fails at connect again, as in v1.8.1. For example,
`collation=utf8mb4_uca1400_ai_ci` without `charset` on MariaDB 11 will
now fail; adding `charset=utf8mb4` fixes it. If you'd rather keep
collation-only lenient, I can drop the error branch instead so only
#1603 is fixed.

3 of 3 new or added lines in 1 file covered. (100.0%)

3929 of 4573 relevant lines covered (85.92%)

1180915.08 hits per line