fix: support escape sequences in single-quoted literals in struct tags - #467
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Pastalikek65 wants to merge 1 commit into
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fix: support escape sequences in single-quoted literals in struct tags#467Pastalikek65 wants to merge 1 commit into
Pastalikek65 wants to merge 1 commit into
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text/scanner only supports single-character char literals, so tags like `parser:"'\n'"` (a literal newline after Go's escape processing) failed with 'literal not terminated', while the equivalent `"\n"` worked. Before scanning a struct tag, rewrite single-quoted literals containing escape sequences or control characters (eg. '\t', '\n', '\'', '\\') as double-quoted strings (with control characters re-escaped for text/scanner). Single-character literals like '=' are left untouched. Fixes alecthomas#249.
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Fixes #249.
Problem
parser:"'\n'"(and'\t','\'','\\', ...) failed to build with:Root cause: the tag lexer (
tagLexer) is based ontext/scanner, whose char literals do not support escape sequences — so a literal newline inside'...'(produced by Go's own escape processing of"\n") caused a scanner error. The equivalent double-quoted form"\n"worked, which is the exact inconsistency reported in the issue.Fix
struct.go: before scanning,quoteEscapedCharLiteralsrewrites any single-quoted literal containing escape sequences or control characters as a double-quoted string, with control characters re-escaped sotext/scanneraccepts them:'\n'(real newline) →"\n"'\t'→"\t"'\''→"'"'\\'→"\\"'a','=', ... (plain single-char literals) are left untouchedBoth forms now behave identically, and
Unquote-style semantics are preserved (the value is the character itself).One new test:
TestEscapedCharLiteralInTag(also covers'\t'and'\\'). Verified against the repro from the issue —TestLiteralNotTerminatedBadnow builds without error.