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The `tools/node_compat/node` submodule has been moved to `tests/node_compat/runner/suite` and the remaining files within `tools/node_compat` to `tests/node_compat/runner`. Most of the changes are of the header within `tests/node_compat/test` files. The `setup` and `test` tasks within `tests/node_comapt` execute successfully. Towards #22525 CC @mmastrac
164 lines
3.6 KiB
Markdown
164 lines
3.6 KiB
Markdown
# Deno Node.js compatibility
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This module is meant to have a compatibility layer for the
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[Node.js standard library](https://nodejs.org/docs/latest/api/).
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**Warning**: Any function of this module should not be referred anywhere in the
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Deno standard library as it's a compatibility module.
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## Supported modules
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- [x] assert
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- [x] assert/strict _partly_
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- [x] async_hooks _partly_
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- [x] buffer
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- [x] child_process _partly_
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- [x] cluster _partly_
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- [x] console _partly_
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- [x] constants _partly_
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- [x] crypto _partly_
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- [x] dgram _partly_
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- [x] diagnostics_channel _partly_
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- [x] dns _partly_
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- [x] events
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- [x] fs _partly_
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- [x] fs/promises _partly_
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- [x] http _partly_
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- [ ] http2
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- [x] https _partly_
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- [x] inspector _partly_
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- [x] module
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- [x] net
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- [x] os _partly_
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- [x] path
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- [x] path/posix
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- [x] path/win32
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- [x] perf_hooks
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- [x] process _partly_
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- [x] punycode
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- [x] querystring
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- [x] readline
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- [x] repl _partly_
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- [x] stream
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- [x] stream/promises
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- [x] stream/web _partly_
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- [x] string_decoder
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- [x] sys
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- [x] timers
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- [x] timers/promises
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- [ ] tls
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- [ ] trace_events
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- [x] tty _partly_
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- [x] url
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- [x] util _partly_
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- [x] util/types _partly_
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- [ ] v8
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- [x] vm _partly_
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- [x] wasi
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- [ ] webcrypto
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- [x] worker_threads
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- [ ] zlib
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* [x] node globals _partly_
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### Deprecated
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These modules are deprecated in Node.js and will probably not be polyfilled:
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- domain
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- freelist
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### Experimental
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These modules are experimental in Node.js and will not be polyfilled until they
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are stable:
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- diagnostics_channel
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- async_hooks
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- policies
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- trace_events
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- wasi
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- webcrypto
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## CommonJS modules loading
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`createRequire(...)` is provided to create a `require` function for loading CJS
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modules. It also sets supported globals.
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```ts
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import { createRequire } from "node:module";
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const require = createRequire(import.meta.url);
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// Loads native module polyfill.
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const path = require("path");
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// Loads extensionless module.
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const cjsModule = require("./my_mod");
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// Visits node_modules.
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const leftPad = require("left-pad");
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```
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## Contributing
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### Setting up the test runner and running tests
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See
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[tests/node_compat/runner/README.md](../../../tests/node_compat/runner/README.md).
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### Best practices
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When converting from promise-based to callback-based APIs, the most obvious way
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is like this:
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```ts, ignore
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promise.then((value) => callback(null, value)).catch(callback);
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```
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This has a subtle bug - if the callback throws an error, the catch statement
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will also catch _that_ error, and the callback will be called twice. The correct
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way to do it is like this:
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```ts, ignore
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promise.then((value) => callback(null, value), callback);
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```
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The second parameter of `then` can also be used to catch errors, but only errors
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from the existing promise, not the new one created by the callback.
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If the Deno equivalent is actually synchronous, there's a similar problem with
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try/catch statements:
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```ts, ignore
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try {
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const value = process();
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callback(null, value);
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} catch (err) {
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callback(err);
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}
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```
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Since the callback is called within the `try` block, any errors from it will be
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caught and call the callback again.
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The correct way to do it is like this:
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```ts, ignore
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let err, value;
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try {
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value = process();
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} catch (e) {
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err = e;
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}
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if (err) {
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callback(err); // Make sure arguments.length === 1
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} else {
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callback(null, value);
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}
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```
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It's not as clean, but prevents the callback being called twice.
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### Remaining Tests
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Node compatibility can be measured by how many native Node tests pass. If you'd
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like to know what you can work on, check out the list of Node tests remaining
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[here](../../../tests/node_compat/runner/TODO.md).
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