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perf(parser): code-unit scanner in DestructiveSqlDetector.stripCommentsAndStrings (#1511) - #1603
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stripCommentsAndStrings compiled a RegExp and copied the rest of the script (sql.substring(i)) at every $, including $1 / $2 parameters, and indexed the text one-character string at a time. The loop now reads code units, with _skipLineComment, _skipBlockComment, _skipDollarQuote and _skipStringLiteral returning the next offset, and appends the untouched text in runs. The WHERE and SET regexes are static. The output is the same; a test compares it with the previous implementation on hand-written and random scripts. Closes #1511
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Summary
`stripCommentsAndStrings` (runs before every destructive-statement check) compiled `RegExp(r'^$([a-zA-Z0-9_]*)$')` and copied the remainder of the script with `sql.substring(i)` at every `$` (so at every `$1`, `$2` parameter), and read the text one one-character string at a time.
Behaviour is unchanged on purpose, including the quirks (a backslash escapes inside single quotes, an unterminated comment / string / dollar quote runs to the end, the line break after a `--` comment is kept). This detector guards destructive statements, so the new tests compare against the previous implementation:
Tests (not run locally; CI will)
`test/core/database/destructive_sql_strip_test.dart` holds the old implementation as the reference and checks hand-written scripts (unterminated forms, `$1`, `$tag$`, surrogate pairs), 3000 seeded random SQL-like strings, and a 20,000-line script.
Closes #1511