Add flag to emit createRequire matching TS nodenext behavior #728
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Progress toward #726 This is currently an opt-in flag handling a nuance in how TS transpiles imports like these: ```ts import foo = require('foo'); ``` In the new nodenext mode when targeting ESM, TS now transforms this code to use `createRequire`. The change is described here: https://devblogs.microsoft.com/typescript/announcing-typescript-4-7/#commonjs-interoperability This PR adds a flag `injectCreateRequireForImportRequire` to enable this different behavior. It's unclear if this should eventually become the default, but it at least seems useful as an option to avoid some ESM/CJS interop frustration. As I understand it, the main benefit of this change over explicit `createRequire` is that it allows a single codebase to be transpiled to Node ESM and Node CJS while using this syntax. A downside is that `createRequire` is Node-specific and needs special support from bundlers, but it looks like webpack can recognize the pattern. In most situations, real ESM `import` syntax is probably preferable, but this syntax makes it possible to force the use of CJS. The ts-node transpiler plugin system expects transpilers to have this mode as an option, so this is a step closer to having a compliant ts-node plugin.
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@@ Coverage Diff @@
## main #728 +/- ##
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Coverage 87.16% 87.17%
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Files 54 54
Lines 5711 5722 +11
Branches 1346 1349 +3
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+ Hits 4978 4988 +10
Misses 466 466
- Partials 267 268 +1
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Benchmark resultsBefore this PR: 393 thousand lines per second Measured change: 0.15% slower (0.96% slower to 0.31% faster) |
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…erce#728) Progress toward alangpierce#726 This is currently an opt-in flag handling a nuance in how TS transpiles imports like these: ```ts import foo = require('foo'); ``` In the new nodenext mode when targeting ESM, TS now transforms this code to use `createRequire`. The change is described here: https://devblogs.microsoft.com/typescript/announcing-typescript-4-7/#commonjs-interoperability This PR adds a flag `injectCreateRequireForImportRequire` to enable this different behavior. I'm gating this behind a flag out of caution, though it's worth noting that TS gives an error when using this syntax and targeting module esnext, so it will likely be safe to switch to this new emit strategy as the default behavior in the future. As I understand it, the main benefit of this change over explicit `createRequire` is that it allows a single codebase to be transpiled to Node ESM and Node CJS while using this syntax. A downside is that `createRequire` is Node-specific and needs special support from bundlers, but it looks like webpack can recognize the pattern. In most situations, real ESM `import` syntax is probably preferable, but this syntax makes it possible to force the use of CJS. The ts-node transpiler plugin system expects transpilers to have this mode as an option, so this is a step closer to having a compliant ts-node plugin.
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Progress toward #726
This is currently an opt-in flag handling a nuance in how TS transpiles imports
like these:
In the new nodenext mode when targeting ESM, TS now transforms this code to use
createRequire. The change is described here:https://devblogs.microsoft.com/typescript/announcing-typescript-4-7/#commonjs-interoperability
This PR adds a flag
injectCreateRequireForImportRequireto enable thisdifferent behavior. I'm gating this behind a flag out of caution, though it's
worth noting that TS gives an error when using this syntax and targeting
module esnext, so it will likely be safe to switch to this new emit strategy as
the default behavior in the future.
As I understand it, the main benefit of this change over explicit
createRequireis that it allows a single codebase to be transpiled to Node ESM and Node CJS
while using this syntax. A downside is that
createRequireis Node-specific andneeds special support from bundlers, but it looks like webpack can recognize the
pattern. In most situations, real ESM
importsyntax is probably preferable,but this syntax makes it possible to force the use of CJS.
The ts-node transpiler plugin system expects transpilers to have this mode as an
option, so this is a step closer to having a compliant ts-node plugin.