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[blog] submit Melange 3 blog post (#168)
* [blog] submit Melange 3 blog post * format * Apply suggestions from code review Co-authored-by: Javier Chávarri <[email protected]> * add section on multiple ocaml versions --------- Co-authored-by: Javier Chávarri <[email protected]>
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| --- | ||
| title: 'Announcing Melange 3' | ||
| date: 2024-02-13 | ||
| author: Antonio Monteiro | ||
| gravatar: 45c2052f50f561b9dc2cae59c777aecd794f57269fa317f9c9c3365c2e00d16f | ||
| twitter: '@_anmonteiro' | ||
| --- | ||
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| We are excited to announce the release of [Melange | ||
| 3](https://github.com/melange-re/melange/releases/tag/3.0.0-51), the latest | ||
| version of our backend for the OCaml compiler that emits JavaScript. | ||
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| This new version comes packed with significant changes, improvements, and a few | ||
| necessary removals to ensure a more streamlined and efficient experience for our | ||
| users. This new version is both leaner and more robust. We focused on fixing | ||
| crashes and removing obsolete functionality, improving the developer and | ||
| troubleshooting experience, increasing OCaml compatibility and JavaScript FFI | ||
| integration. | ||
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||
| --- | ||
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| Here's a rundown of the key updates in Melange 3. Check the [Melange | ||
| documentation](https://melange.re/v3.0.0/) for further resources. | ||
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| ## Major Changes and Removals | ||
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| In Melange 3, `Belt` is no longer a dependency for the Melange `Stdlib`. | ||
| Libraries that depend on the Belt modules will need to include `(libraries | ||
| melange.belt)` in their build configuration. | ||
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| The `@bs` / `@bs.*` attributes have been replaced. Users of Melange should now | ||
| utilize `[@u]` for uncurried application and `[@mel.*]` for FFI attributes. | ||
| Additionally: | ||
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| - `[@mel.val]` has been removed as it was redundant in the Melange FFI. | ||
| - `[@mel.splice]` was removed in favor of `[@mel.variadic]` | ||
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| For this release, most modules in the `Js` namespace had their APIs unified, | ||
| deduplicated and refactored. In cases such as `Js.Int`, `Js.Date`, `Js.Re`, | ||
| `Js.Float`, `Js.String`, some functions were changed from pipe-first to | ||
| pipe-last and labeled arguments were added; and incorporating those made others | ||
| obsolete, which we removed. Modules such as `Js.List`, `Js.Null_undefined`, | ||
| `Js.Option`, `Js.Result` and `Js.Cast` are also no longer present in Melange 3. | ||
| Alternatives within `Stdlib` or `Belt` are instead recommended. | ||
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| ## New Features and Enhancements | ||
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| Melange 3 includes a few interesting new features and enhancements. From syntax | ||
| and preprocessing to interop with JavaScript, runtime and error messages, here are some | ||
| we chose to highlight: | ||
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| ### Multiple OCaml-version releases | ||
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| A few users have expressed concerns related to Melange having a 1:1 relationship to its | ||
| OCaml version. This limitation exists because we vendor and modify OCaml's typechecker, | ||
| which is usually version-dependent. | ||
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| In Melange 1, we made some strides to solve this at the syntax level – one Melange version | ||
| could work across many compiler switches. But that has a pretty big limitation: editor tooling, | ||
| documentation generation and everything else that reads from `.cmt` artifact files needed to be | ||
| in the same compiler switch as the version of the typechecker in use. | ||
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| Starting in Melange 3, we will be adopting the recent Merlin release strategy: Melange has a | ||
| release for every compiler version that it supports, suffixed with the OCaml version that it | ||
| corresponds to, e.g. Melange 3 on OCaml 4.14 is `v3.0.0-414`. | ||
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| ### Interop | ||
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| - Modules can be renamed with `@mel.as` | ||
| - `@mel.obj` and `%mel.obj` allow renaming the JS object keys with `@mel.as` | ||
| - `@mel.new` can now be used alongside `@mel.send` and `@mel.send.pipe` | ||
| - `[@@deriving abstract]` is now deprecated and split into its two main | ||
| features: | ||
| - `[@@deriving jsProperties]` derives a JS object creation function that can | ||
| generate a JS object with optional keys (when using `@mel.optional]`) | ||
| - `[@@deriving getSet]` derives getter / setter functions for the JS object | ||
| derived by the underlying record. | ||
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| ### Error messages & Hints | ||
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| Melange 3 provides more informative error messages originating from both the | ||
| `melange.ppx` and the compiler core. | ||
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| In this release, we also introduce a new `unprocessed` alert to detect code that | ||
| has made it to the Melange compiler without having been processed by the Melange | ||
| PPX. Besides hinting users to add `(preprocess (pps melange.ppx))` to their `dune` | ||
| file, this alert more explicitly exposes a common failure mode that puzzles | ||
| beginners quite often. | ||
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| Additionally: | ||
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| - The Melange playground now has improved reporting of PPX alerts. | ||
| - Runtime error rendering in the playground renders better error information. | ||
| - The JS parser within Melange has been upgraded to Flow v0.225.1. | ||
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| ### Runtime & `Stdlib` | ||
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| Melange 3 implements more functions in the following modules of the `Stdlib`: | ||
| `String`, `Bytes`, `Buffer`, `BytesLabels` and `StringLabels`. Specifically, the | ||
| new unicode parsing functions upstream are now available in Melange as well. | ||
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| Some keys with legacy names have been updated for consistency, such as renaming | ||
| `RE_EXN_ID` to `MEL_EXN_ID` and `BS_PRIVATE_NESTED_SOME_NONE` to | ||
| `MEL_PRIVATE_NESTED_SOME_NONE` in the Melange generated JS runtime. | ||
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| The team also took a look at unicode strings in this version of Melange. A few | ||
| noteworthy changes: | ||
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| - `{j| ... |j}` interpolation now only allows interpolating strings; other | ||
| usages of interpolation have started to produce type errors. | ||
| - Unicode strings such as `{js| … |js}` can now be used as `Format` strings. | ||
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| ## Conclusion | ||
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| Melange 3 marks a significant step forward in the OCaml-to-JavaScript | ||
| compilation process. With these updates, we aim to provide a more robust, | ||
| efficient, and user-friendly tool for developers. We encourage users to upgrade | ||
| to this new version to take full advantage of the improvements and to adapt to | ||
| the breaking changes for a smoother development experience. For a full list of | ||
| the changes that made it into this release, feel free to consult the | ||
| [changelog](https://github.com/melange-re/melange/blob/main/Changes.md#300-2024-01-28). | ||
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| Stay tuned for more updates and enhancements as we continue to improve Melange | ||
| and support the developer community! |