robertogallok opened a new pull request, #2523:
URL: https://github.com/apache/datafusion-sqlparser-rs/pull/2523
`Ident::Display` reuses the string-literal escaper, which guesses whether a
delimiter inside the value is already escaped. An `Ident` value is always the
decoded name, so the guess corrupts identifiers whose name contains two
adjacent delimiters or a backslash before one:
```rust
let ast = Parser::parse_sql(&GenericDialect {}, r#"SELECT
"a""""b""#).unwrap(); // identifier a""b
println!("{}", ast[0]); // SELECT "a""b" -> parses back as the
identifier a"b
```
The same happens with backticks (`` `a````b` ``) and with a value such as
`a\"b`, which displays as `"a\"b"` and no longer parses.
The fix doubles every delimiter unconditionally, streaming into the
formatter without allocating. Bracket identifiers are left untouched because
#2418 already covers them.
`with_unescape(false)` keeps the raw doubled delimiters in the value, and
one `Display` cannot serve both readings of the same value. This change chooses
the default mode, so the two MySQL tests that asserted a display round trip in
no-escape mode now assert only the parsed AST.
Tests: a round trip for consecutive delimiters in `"` and `` ` ``
identifiers, plus an exhaustive round trip over every value of length 1..=4
built from the delimiter, a backslash, an ASCII and a multi-byte character,
across all dialects that delimit identifiers with that character. The
exhaustive test fails on `main` (smallest failing value: `""`).
AI assistance was used to draft this change; I reviewed and ran the tests,
`cargo fmt` and `cargo clippy`.
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