[JSONSelection] Fix precedence of parsing NamedPathSelection within NamedSelection rule
#5156
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CI performance tests
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benjamn
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May 13, 2024
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| impl NamedSelection { | ||
| fn parse(input: &str) -> IResult<&str, Self> { | ||
| alt(( | ||
| // We must try parsing NamedPathSelection before NamedFieldSelection | ||
| // and NamedQuotedSelection because a NamedPathSelection without a | ||
| // leading `.`, such as `alias: some.nested.path` has a prefix that | ||
| // can be parsed as a NamedFieldSelection: `alias: some`. Parsing | ||
| // then fails when it finds the remaining `.nested.path` text. Some | ||
| // parsers would solve this by forbidding `.` in the "lookahead" for | ||
| // Named{Field,Quoted}Selection, but negative lookahead is tricky in | ||
| // nom, so instead we greedily parse NamedPathSelection first. | ||
| Self::parse_path, | ||
| Self::parse_field, | ||
| Self::parse_quoted, | ||
| Self::parse_path, | ||
| Self::parse_group, |
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This is the operative change that fixes the NamedPathSelection parsing ambiguity.
JSONSelection] Fix precedence of parsing NamedPathSelection within NamedSelection rule
JSONSelection] Fix precedence of parsing NamedPathSelection within NamedSelection ruleNamedPathSelection within NamedSelection rule
lennyburdette
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May 13, 2024
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This is a follow-up to PR #5156, which reordered some rules in the JSONSelection grammar but neglected to regenerate the SVG diagrams.
benjamn
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This is a follow-up to PR #5156, which reordered some rules in the JSONSelection grammar but neglected to regenerate the SVG diagrams.
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Thanks to @lennyburdette's playground, I quickly found a bug with the parsing of
NamedPathSelection. This PR adds a number of regression tests and fixes the bug.I updated the
README.mdto emphasize the importance of parsingNamedPathSelectionbeforeNamedFieldSelectionandNamedQuotedSelection, so just read those changes if you're curious why this solution makes sense for a parser like this one.