[cli] Avoid SourceMapGenerator for simple map concatenation
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This removes the last use of `source-map` package from babel-cli. Instead, we use a [SectionedSourceMap](https://github.com/jridgewell/trace-mapping/blob/8db5df070b15e2a669277b710a9d69ad0676524d/src/types.ts#L28-L32), which is purpose built for simple file concatenation like this. This should be considerably faster to generate sourcemaps now. And, if a sourcemaps are not needed, it's essentially free. As an added benefit, this gives us proper `names` support: ```diff --- a 2022-04-20 11:01:49.000000000 -0400 +++ b 2022-04-20 11:01:55.000000000 -0400 @@ -1,12 +1,17 @@ { "version": 3, "file": "script2.js", - "names": [], + "names": [ "arr", "map", "x", "MULTIPLIER" ], "sources": [ "script.js" ], "sourcesContent": [ "arr.map(x => x * MULTIPLIER);" ], - "mappings": ";;AAAA,GAAG,CAAC,GAAJ,CAAQ,UAAA,CAAC;AAAA,SAAI,CAAC,GAAG,UAAR;AAAA,CAAT" + "mappings": ";;AAAAA,GAAG,CAACC,GAAJ,CAAQ,UAAAC,CAAC;AAAA,SAAIA,CAAC,GAAGC,UAAR;AAAA,CAAT" } ```
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Build successful! You can test your changes in the REPL here: https://babeljs.io/repl/build/51708/ |
JLHwung
approved these changes
Apr 20, 2022
JLHwung
added
PR: Bug Fix 🐛
| function countNewlines(code: string): number { | ||
| let count = 0; | ||
| let index = -1; | ||
| while ((index = code.indexOf("\n", index + 1)) !== -1) { |
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I think we need to handle all the possible newlines. Even if we always print \n, multiline template literals may still contain different line terminators.
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This is just a faster version of the code.split("\n").length that was there before. We can add more newline support, could we wait until a followup?
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Oh ok sure, I didn't realize it was already like this 👍 (and no one ever complained, so it's super low priority).
nicolo-ribaudo
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SourceMapGenerator for simple map concatenation
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@jridgewell/trace-mappingand removes ancientsource-mapThis removes the last use of
source-mappackage from babel-cli. Instead, we use a SectionedSourceMap, which is purpose built for simple file concatenation like this.This should be considerably faster to generate sourcemaps now. If sourcemaps are not needed, it's essentially free. And as an added benefit, this gives us proper
namessupport:(That fifth letter that appears in some mappings segments is the
namespointer)