Handle "simple" (missing origin) source mappings in minifier output #928
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…acebook#928) Summary: Pull Request resolved: facebook#928 Fixes facebook#927 Terser, unlike the previous default minifier UglifyES, produces source maps whose entries may contain "simple mappings" - that is entries with a generated line+col but no original location. When Metro processes minified output ahead of serialization, it doesn't correctly handle these entries. Instead it incorrectly detects them as complete mappings and produces a merged source map with `-1` origin line numbers in place of simple mappings. Some tools will reject the whole source map (which is otherwise correct) based on the appearance of a negative line number. The issue comes down to the conversion of raw mappings to `BabelSourceMapSegments` in `toBabelSegments`, which currently generates entries for simple mappings with `null` `origin` *properties*, such as: ``` { generated: { column: 2, line: 1 }, origin: { column: null, line: null }, // ... } ``` According to the Flow type for `BabelSourceMapSegments`, that's incorrect. `origin` itself is optional and should be missing - the properties of `origin` are not nullable. Based on the presence of the `origin` property in that object, `toSegmentTuple` generates a 4-tuple and we go on to add a "source mapping" rather than a "simple mapping". This fixes `toBabelSegments` to omit `origin` unless `line` and `column` are both populated. The final source map output is then correct. Changelog: [Fix] Source maps may have invalid entries when using Terser minification. Reviewed By: motiz88 Differential Revision: D43351987 fbshipit-source-id: 706cf2e90cb33ebc8223b449b2c280156512c9a4
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…928) Summary: Pull Request resolved: #928 Fixes #927 Terser, unlike the previous default minifier UglifyES, produces source maps whose entries may contain "simple mappings" - that is entries with a generated line+col but no original location. When Metro processes minified output ahead of serialization, it doesn't correctly handle these entries. Instead it incorrectly detects them as complete mappings and produces a merged source map with `-1` origin line numbers in place of simple mappings. Some tools will reject the whole source map (which is otherwise correct) based on the appearance of a negative line number. The issue comes down to the conversion of raw mappings to `BabelSourceMapSegments` in `toBabelSegments`, which currently generates entries for simple mappings with `null` `origin` *properties*, such as: ``` { generated: { column: 2, line: 1 }, origin: { column: null, line: null }, // ... } ``` According to the Flow type for `BabelSourceMapSegments`, that's incorrect. `origin` itself is optional and should be missing - the properties of `origin` are not nullable. Based on the presence of the `origin` property in that object, `toSegmentTuple` generates a 4-tuple and we go on to add a "source mapping" rather than a "simple mapping". This fixes `toBabelSegments` to omit `origin` unless `line` and `column` are both populated. The final source map output is then correct. Changelog: [Fix] Source maps may have invalid entries when using Terser minification. Reviewed By: motiz88 Differential Revision: D43351987 fbshipit-source-id: 5cd46fdd001f3c3a3599ada44f525bec467854e1
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…928) Summary: Pull Request resolved: #928 Fixes #927 Terser, unlike the previous default minifier UglifyES, produces source maps whose entries may contain "simple mappings" - that is entries with a generated line+col but no original location. When Metro processes minified output ahead of serialization, it doesn't correctly handle these entries. Instead it incorrectly detects them as complete mappings and produces a merged source map with `-1` origin line numbers in place of simple mappings. Some tools will reject the whole source map (which is otherwise correct) based on the appearance of a negative line number. The issue comes down to the conversion of raw mappings to `BabelSourceMapSegments` in `toBabelSegments`, which currently generates entries for simple mappings with `null` `origin` *properties*, such as: ``` { generated: { column: 2, line: 1 }, origin: { column: null, line: null }, // ... } ``` According to the Flow type for `BabelSourceMapSegments`, that's incorrect. `origin` itself is optional and should be missing - the properties of `origin` are not nullable. Based on the presence of the `origin` property in that object, `toSegmentTuple` generates a 4-tuple and we go on to add a "source mapping" rather than a "simple mapping". This fixes `toBabelSegments` to omit `origin` unless `line` and `column` are both populated. The final source map output is then correct. Changelog: [Fix] Source maps may have invalid entries when using Terser minification. Reviewed By: motiz88 Differential Revision: D43351987 fbshipit-source-id: 5cd46fdd001f3c3a3599ada44f525bec467854e1
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Summary:
Fixes #927
Terser, unlike the previous default minifier UglifyES, produces source maps whose entries may contain "simple mappings" - that is entries with a generated line+col but no original location.
When Metro merges source maps to serialize minified output, it doesn't correctly handle these entries. Instead it incorrectly detects them as complete mappings and produces a merged source map with
-1origin line numbers in place of simple mappings.Some tools will reject the whole source map (which is otherwise correct) based on the appearance of a negative line number.
The issue comes down to the conversion of raw mappings to
BabelSourceMapSegmentsintoBabelSegments, which currently generates entries for simple mappings withnulloriginproperties, such as:According to the Flow type for
BabelSourceMapSegments, that's incorrect.originitself is optional and should be missing - the properties oforiginare not nullable.Based on the presence of the
originproperty in that object,toSegmentTuplegenerates a 4-tuple and we go on to add a "source mapping" rather than a "simple mapping".This fixes
toBabelSegmentsto omitoriginunlesslineandcolumnare both populated. The final source map output is then correct.Differential Revision: D43351987