doc: fix filehandle.truncate sample codes #20913
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doc/api/fs.md
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| const fd = await fsPromises.open('temp.txt', 'r+'); | ||
| await fsPromises.ftruncate(fd, 4); | ||
| const filehandle = await fsPromises.open('temp.txt', 'r+'); | ||
| await filehandle.truncate(4); | ||
| console.log(fs.readFileSync('temp.txt', 'utf8')); // Prints: Node |
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these should really be....
let filehandle;
try {
const filehandle = await fsPromises.open('temp.txt', 'r+');
await filehandle.truncate(4);
} finally {
await filehandle.close();
}While the filehandle will close automatically on garbage collection in order to prevent the leak, it should be closed manually. A process warning would be emitted if it is allowed to close on gc.
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@jasnell sorry for the tangent: we really need a better resources story in general - if this is tricky consider how hard this is with 3 concurrent handles.
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One thing that might work here API wise is a disposer:
await fsPromises.open('temp.txt', 'r+', async handle => {
await handle.truncate(4);
});This doesn't solve the harder problem of dealing with multiple resources at once though.
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@jasnell
Thank you for your comment. The codes were fixed with filehandle.close. Please check them again.
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@jasnell - what do you think the right avenue to discuss such a cross-cutting concern is? I'm not sure what the right team/working-group/avenue is.
I'm a little lost here :)
Fix sample codes because `filehandle.close` was not called when error occured. `filehandle.close` should be called manually.
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Collaborators - please 👍 if you agree with fast-tracking this. |
doc/api/fs.md
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| filehandle = await fsPromises.open('temp.txt', 'r+'); | ||
| await filehandle.truncate(4); | ||
| } finally { | ||
| if (filehandle !== null) { |
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What can make undefined filehandle be null?
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The open throwing, since that was unclear it'll definitely be unclear for some users - we should probably add a comment.
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If open throws, will not the filehandle remain undefined?
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I could have sworn that was a != and not a !==, good spotting!
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I mean, shoud not we initialize filehandle as null or use non-strict comparison or even if (filehandle) ?
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We should. I was saying "good spotting" for spotting that.
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Sorry, GitHub did not update timely with new comments)
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@vsemozhetbyt @benjamingr
filehandle is not undefined. It is defined and initialized as null.
let filehandle;But it is unclear for some users.
The below code may be more clearly for users. It looks better?
async function doTruncate() {
let filehandle = null;
try {
filehandle = await fsPromises.open('temp.txt', 'r+');
await filehandle.truncate(4);
} finally {
if (filehandle) {
// close the file if it is opened.
await filehandle.close();
}
}
console.log(fs.readFileSync('temp.txt', 'utf8')); // Prints: Node
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let filehandle;
When you do that in JavaScript that initializes the value to undefined. You can verify this in the following script:
let filehandle;
console.log(filehandle);The below code may be more clearly for users. It looks better?
Yes, thank you.
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@benjamingr
oh, sorry! I was wrong and fixed them.
doc/api/fs.md
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| console.log(fs.readFileSync('temp.txt', 'utf8')); // Prints Node.js\0\0\0 | ||
| } | ||
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| doTruncate().catch(console.error); | ||
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Nit: unneeded empty line.
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@vsemozhetbyt Fixed it. Thanks.
Fix sample codes for filehandle.truncate to make them more clearly.
vsemozhetbyt
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CI-lite: https://ci.nodejs.org/job/node-test-pull-request-lite/749/ (one unrelated fail of a flaky test). |
vsemozhetbyt
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author ready
PR-URL: #20913 Reviewed-By: James M Snell <[email protected]> Reviewed-By: Benjamin Gruenbaum <[email protected]> Reviewed-By: Vse Mozhet Byt <[email protected]> Reviewed-By: Ruben Bridgewater <[email protected]> Reviewed-By: Rich Trott <[email protected]>
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Landed in ac82261 |
PR-URL: #20913 Reviewed-By: James M Snell <[email protected]> Reviewed-By: Benjamin Gruenbaum <[email protected]> Reviewed-By: Vse Mozhet Byt <[email protected]> Reviewed-By: Ruben Bridgewater <[email protected]> Reviewed-By: Rich Trott <[email protected]>
Checklist
make -j4 test(UNIX), orvcbuild test(Windows) passes