Comment-related warnings when building with Vite #1916
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kblcuk
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to kblcuk/fp-ts
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Jan 3, 2024
Currently there are some arrow functions that have /*#__PURE__*/ annotation before function call to identify that that function call is side effect free. However since this project is built to es5 target, which doesn't have arrow functions support, the code is then translated into regular function that loos something like this: ``` /** @internal */ export var flatMapNullable = function (F, M) { /*#__PURE__*/ return dual(3, function (self, f, onNullable) { return M.flatMap(self, liftNullable(F)(f, onNullable)); }); }; ``` However this makes some built tools (Vite (which uses Rollup under the hood) in our case) unhappy, and build produces a lot of warnings about that __PURE__ annotation being in the wrong place. Checking the Rollup docs [0], it seems that pure annotation should be placed right before function invocation, so in this particular case between `return` keyword and the actual function. So this simply changes arrow functions in question to have explicit return keyword and annotation before the function call, which leaves no interpretation to ts compiler, and makes our code build process warning-free. This also potentially fixes gcanti#1916 [0] https://rollupjs.org/configuration-options/#pure
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FIY I stumbled upon the same issue and after some investigation I think I might have a fix 馃 |
gcanti
pushed a commit
that referenced
this issue
Jan 3, 2024
Currently there are some arrow functions that have /*#__PURE__*/ annotation before function call to identify that that function call is side effect free. However since this project is built to es5 target, which doesn't have arrow functions support, the code is then translated into regular function that loos something like this: ``` /** @internal */ export var flatMapNullable = function (F, M) { /*#__PURE__*/ return dual(3, function (self, f, onNullable) { return M.flatMap(self, liftNullable(F)(f, onNullable)); }); }; ``` However this makes some built tools (Vite (which uses Rollup under the hood) in our case) unhappy, and build produces a lot of warnings about that __PURE__ annotation being in the wrong place. Checking the Rollup docs [0], it seems that pure annotation should be placed right before function invocation, so in this particular case between `return` keyword and the actual function. So this simply changes arrow functions in question to have explicit return keyword and annotation before the function call, which leaves no interpretation to ts compiler, and makes our code build process warning-free. This also potentially fixes #1916 [0] https://rollupjs.org/configuration-options/#pure
How is the fix going? :) |
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馃悰 Bug report
Current Behavior
When building a production bundle with Vite, I get a bunch of warnings like this:
Expected behavior
No build warnings.
Reproducible example
vite build.You should be able to see the warnings in the build log.
Suggested solution(s)
Not sure - probably fix the comments somehow?
Your environment
Which versions of fp-ts are affected by this issue?
Did this work in previous versions of fp-ts?
Not sure - we just transitioned away from Create React App (where we didn't get these warnings) to Vite recently.
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