Add gleam support to Mix #14262

Papipo · 2025-02-13T09:55:10Z

This PR adds support for the gleam language.

Support for gleam.toml in path deps
Support gleam in deps loader.
Support for gleam in deps.compile
Require specific gleam binary version (hardcoded to 1.9.0 for now, see below)
Handle absent gleam binary
Support git deps (support for them in gleam is in main already but not yet released)
Support for :application option in Mix.ProjectStack.push (thus an application function is not needed)
Setup gleam on CI (Otherwise gleam tests will be skipped).

Notes:

Packages having a gleam binary version requirements are handled automatically when executing gleam compile-package.
The gleam binary version requirement for mix integration is hardcoded because I could just try to run gleam export package-info but I can't know the reason for a bad exit status (maybe the dep path was wrong and the command was run in a dir without a gleam.toml).
The required command to export information about gleam packages and their deps ~~is not yet released but has already been merged. Should land on v1.10.0.~~ Was released on v1.10.0

lib/mix/lib/mix/gleam.ex

lib/mix/lib/mix/tasks/deps.compile.ex

Papipo · 2025-02-17T09:02:55Z

@josevalim when working on this I was always thinking of erlang target packages, but it would be nice to be able to use javascript ones as well (ie. to use them in Phoenix frontend). Not sure how we can handle that, any hints?

josevalim · 2025-02-17T09:55:52Z

It should be possible because we use heroicons, a regular JS package, as a dependency on Phoenix applications. So we could probably support a :gleam_targets or similar option that is used by by deps.compile? You will probably need to set app: false true, similar to how heroicons are added.

lpil · 2025-02-17T13:24:48Z

Hello! You shouldn't need to do anything special target-wise as Gleam performs dead code elimination for code that is for other targets.

@josevalim when working on this I was always thinking of erlang target packages, but it would be nice to be able to use javascript ones as well (ie. to use them in Phoenix frontend). Not sure how we can handle that, any hints?

I would not expect Mix to become a front-end build tool by adding Gleam support. I think the workflow should be the same as it is today etc, with the desired build tool (esbuild, webpack, gleam etc) being run as a Phoenix watcher.

Adding frontend dependencies to the BEAM application dependency tree would either be wasted work compiling and managing them, or the programmer would need to go through every dependency in the lock file and add configuration to their mix.exs for each one they don't want to use on the backend.

We are going to #14262 (comment), so I also need the target config, if any. I think that just exporting everything is the best bet.

There is no such config. A Gleam package doesn't have an explicit target, each function in the public API is available on Erlang, JavaScript, or both, and they get either compiled or eliminated as needed. Whether a package is for Erlang or JavaScript is typically a matter of how the dependant is using them, not a matter of the configuration of the dependency.

There is a target flag in gleam.toml, but that is "if I run code from this page (almost always the tests) what target should be used by default, unless otherwise specified".

lib/mix/lib/mix/tasks/deps.compile.ex

josevalim · 2025-02-20T12:18:08Z

lib/mix/test/test_helper.exs

@@ -269,6 +269,15 @@ Enum.each(fixtures, fn fixture ->
  File.cp_r!(source, dest)
 end)

+## Set up Gleam fixtures
+


And we should probably skip gleam tests if gleam is not installed, right?

Done. I guess I need to add gleam to CI (although I need to wait until my gleam PR is merged and released).

Papipo · 2025-03-26T08:54:36Z

I am kind of copypasting this from the Gleam discord in case someone wants to try this out before merging into main:

What is this?

These changes add first-class support for Gleam in Elixir's Mix, thus allowing gleam path dependencies in mix.exs.
Those dependencies are expected to be 100% valid gleam projects and as such need to have a gleam.toml file.

What's missing?

Probably nothing. Work on the gleam compiler is already merged and work on the Mix side is completed, but there might me rough edges, that's what we need to test.

Instructions

Mix integration will expect you to have gleam >= 1.10.0 installed and that hasn't been released yet. So:

Install Gleam using the nightly release.
- Notice that some package managers might allow you to install it this way.
Grab this elixir branch.
Edit lib/mix/lib/mix/gleam.ex and replace @required_gleam_version with 1.9.0.
Run make in the root folder of the Elixir project and add its bin folder to your $PATH

If you were using mix_gleam, undo its setup.

Usage

After running mix deps.get the Mix workflow doesn't change. deps.compile should compile Gleam path deps.
If you use gleam code from your elixir app, it should just work (as long as you have a gleam.toml file - you might want to move gleam code to a sibling folder or into gleam/src) I think that otherwise the mix.exs file will take precedence over the gleam one.

What needs to be tested?

Anything related to Erlang/OTP shenanigans (.app files, extra_applications and ensuring those start, etc.)
If you have an existing project using mix_gleam, that's a great opportunity to replace it with this.
Gleam Git dependencies.
Just try to break it please.

Thanks

Just report back with your findings and: thanks :person_bowing:

Note: I hope these instructions are enough and correct. Let me know if that's not the case.

lib/mix/lib/mix/tasks/deps.compile.ex

josevalim · 2025-03-26T09:02:29Z

@Papipo thanks for all the work so far!

One question: I thought that gleam shipped as a Hex package, so wouldn't it be possible for the user to depend on the gleam package or similar instead of us depending on a system wide gleam installation?

Papipo · 2025-03-26T09:08:58Z

@Papipo thanks for all the work so far!

One question: I thought that gleam shipped as a Hex package, so wouldn't it be possible for the user to depend on the gleam package or similar instead of us depending on a system wide gleam installation?

No, gleam is a single binary written in Rust. I don't know if we can provide a hex archive maybe? I don't know how these work.

How is rebar installation handled? I know that mix is able to install it locally, but I am not sure what that means exactly. It's still a binary as well, right?

josevalim · 2025-03-26T09:14:48Z

For Rebar, we have some binaries which we upload to hex.pm, and we version control them every year or so. Although I don't think this will work for Gleam, because people want to upgrade it more frequently, and Rebar is only a build tool, not really a compiler. So I guess we need to be clear we are using the system one and it is up to them to enforce the team uses the same version across the board (which is how we deal with make and the elixir executable itself).

Papipo · 2025-03-26T09:17:26Z

For Rebar, we have some binaries which we upload to hex.pm, and we version control them every year or so. Although I don't think this will work for Gleam, because people want to upgrade it more frequently, and Rebar is only a build tool, not really a compiler. So I guess we need to be clear we are using the system one and it is up to them to enforce the team uses the same version across the board (which is how we deal with make and the elixir executable itself).

In fact the binary is also the LS, so you definitely want to have full control of the version you are using, etc.

josevalim · 2025-04-02T13:20:20Z

Quoting @lpil on the forums:

The Gleam compiler only generates Erlang from Gleam modules, but it doesn’t know what any Elixir modules in the package expand to, so it cannot create .app files unless it owns the whole project and so will be performing Elixir and Erlang compilation. This means that any build tool that uses the Gleam compiler will need to generate the required BEAM .beam and .app files.

Apologies but I am a bit confused. We are using gleam compile-package which emits the .beam files already, right? Here is what we invoke: https://github.com/elixir-lang/elixir/pull/14262/files#diff-da9fa810e81e1fe6ac8d4defde11dc457f0066fc9e442e85a96ea2e182414eacR336 - in this case, doesn't Gleam already own the whole package? We don't invoke anything else so if additional steps are necessary, they are not being executed here.

The .app file has things like app name, version, description, registered processes, app environment, and module names. We would need to lift all of this information from the Gleam .toml and make assumptions on how Gleam wants those be used. Worst case scenario, couldn't Gleam support an --app file on compile-package that generates it, based on the outputs of its --out directory?

Papipo · 2025-04-02T14:44:06Z

Yes, compile-package does emit beam files.

From @lpil comment over elixirforum I assume the problem are colocated Elixir files within a Gleam project. The Gleam compiler knows nothing about them so any modules they define can't be written in the .app file, I guess.

What I have done here is use the Mix task to generate the .app file (and inject the two options gleam.toml supports for the erlang target: mod and extra_applications). As you can see we now have a full-fledged .app file.

Let me know if this looks good or if I should revert it. Thanks.

josevalim · 2025-04-02T16:00:32Z

Yes, for collocated projects that’s the responsibility of Mix, but for packages I would say that’s Gleam responsibility. Otherwise there is even more we need to understand from Gleam TOML’s and we may need to keep track of it as it evolves. So is there a chance for it to emit an .app file either by default or via a flag? On the plus side, if Rebar wants to integrate Gleam as well, they can reuse it to emit apps too. :)

Papipo · 2025-04-07T07:28:27Z

Apparently this seems to be working fine except that people sometimes need to compile twice . Could this be code path related maybe? It's probably something stupid I missed.

lpil · 2025-04-08T09:41:23Z

Oh! That's a good idea, much easier.

I think I would prefer to not have Gleam generate the mix.exs as it's intended to be agnostic to any other tooling or language.

Papipo · 2025-04-09T11:43:07Z

Implementation wise, I wonder if perhaps we should drop a mix.exs in disk and then just call mix_dep? This way we trigger the compilation as any other Elixir package.

From what I've seen, we could dump the [erlang] options from gleam.toml directly into the mix.exs application function. The alternative would be to support only specific options but this would require more maintenance.

If gleam options there adhere to the expected format (which I hope is the same as Erlang's) we should be good with the former, no?

josevalim · 2025-04-09T13:51:45Z

Yes, exactly.

Papipo · 2025-04-10T15:34:43Z

If the root Mix project has a path dependency on a gleam dependency, where should I put this mix.exs? Since the code isn't copied over to /deps I would be tampering with the local project.

josevalim · 2025-04-10T16:30:59Z

oh, that would be a problem with this approach. So maybe, instead of writing the file to disk, you should just push the project data, like we do on Mix.install? https://github.com/elixir-lang/elixir/blob/main/lib/mix/lib/mix.ex#L930-L934

It does have one issue though, in that we would have no way to pass application properties (because there is no def application) but perhaps we can fix that by changing compile.app to read also look for an :application key in the project config.

lib/mix/lib/mix/gleam.ex

lib/mix/test/fixtures/gleam_dep/.gitignore

lib/mix/lib/mix/gleam.ex

lib/mix/lib/mix/tasks/deps.ex

lib/mix/lib/mix/dep/loader.ex

lib/mix/test/mix/gleam_test.exs

Papipo · 2025-04-18T20:21:53Z

It does have one issue though, in that we would have no way to pass application properties (because there is no def application) but perhaps we can fix that by changing compile.app to read also look for an :application key in the project config.

I still need to add support for that but the rest is already working. Can you please verify that how I am using ProjectStack.push is sound and as you expected?

I'll add support for :application option to compile.app, handle @eksperimental suggestions and squash because the commit history here isn't the cleanest.

eksperimental

Using ~w and ~W sigils is more idiomatic when passing command line args

lib/mix/lib/mix/gleam.ex

lib/mix/lib/mix/tasks/deps.compile.ex

Papipo · 2025-04-23T15:49:30Z

Using ~w and ~W sigils is more idiomatic when passing command line args

@eksperimental I am somehow having trouble with spaces in paths when using the sigils:

"--out", "/home/papipo/dev/elixir/lib/mix/tmp/get", "and", "compile", "dependencies/_build/dev/lib/gleam_stdlib",

It's splitting the string by spaces in the path.

eksperimental · 2025-04-24T00:09:57Z

Using ~w and ~W sigils is more idiomatic when passing command line args

@eksperimental I am somehow having trouble with spaces in paths when using the sigils:

"--out", "/home/papipo/dev/elixir/lib/mix/tmp/get", "and", "compile", "dependencies/_build/dev/lib/gleam_stdlib",

It's splitting the string by spaces in the path.

Good catch!
Unfortunately the ~w sigil with split the contents even if the white-spaces are escaped, so you we will have to make do without the sigil then.

eksperimental · 2025-04-24T00:20:01Z

Using ~w and ~W sigils is more idiomatic when passing command line args

@eksperimental I am somehow having trouble with spaces in paths when using the sigils:

"--out", "/home/papipo/dev/elixir/lib/mix/tmp/get", "and", "compile", "dependencies/_build/dev/lib/gleam_stdlib",

It's splitting the string by spaces in the path.

This is a hybrid solution. No sure if the clearest, so it's your call whatever you think works best.

~w(compile-package --no-beam --target erlang --package #{package}) ++ ["--out", out, "--lib", lib]

- Add Mix.Gleam module - Add specific gleam binary version requirement - Rely on `gleam export package-info`

- shell_cmd! wasn't handling tuples - Fix documentation

This is an optional value within [erlang] in the gleam.toml file. It will be used for the `mod` value when generating a .app file

Co-authored-by: Eksperimental <eksperimental@autistici.org>

Papipo · 2025-04-24T11:54:04Z

It does have one issue though, in that we would have no way to pass application properties (because there is no def application) but perhaps we can fix that by changing compile.app to read also look for an :application key in the project config.

@josevalim that's implemented and everything seems to be working fine. I think I have a flaky spec in dep_test.exs line 118. If I run that file alone it passes, if I run the whole suite it fails. I know it uses Compile.App, but should be using the project config, not the :application key, although it must be related to these changes since it complains about a missing .app file.

Apart from that, the only thing missing is adding gleam to CI if we don't want to skip those tests, which I assume is the case.

josevalim · 2025-04-24T12:00:15Z

Thank you. Yes, we should add Gleam to the CI. :)

Keep in mind though I am going for holidays and then preparing for ElixirConf, so it may take a while before I get to fully review this. Apologies.

Papipo · 2025-04-24T12:17:27Z

Keep in mind though I am going for holidays and then preparing for ElixirConf, so it may take a while before I get to fully review this. Apologies.

No problem, enjoy your trips!

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Add command to export deps/config gleam-lang/gleam#4240

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Papipo changed the title ~~[DRAFT] Add gleam support to Mix~~ Add gleam support to Mix Mar 26, 2025

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Papipo and others added 13 commits April 24, 2025 13:10

Add fixture for gleam support

4997e6a

Add Gleam integration with Mix

04eede4

- Add Mix.Gleam module - Add specific gleam binary version requirement - Rely on `gleam export package-info`

Add support for git dependencies in gleam packages

edf35ca

Exclude gleam tests if gleam is missing

94c7624

Fix deps.compile for gleam

e81ec1e

- shell_cmd! wasn't handling tuples - Fix documentation

Add support for application_start_module

c595cf6

This is an optional value within [erlang] in the gleam.toml file. It will be used for the `mod` value when generating a .app file

Handle gleam extra_applications

60f5625

Remove redundant quotes

047871e

Do not force app: false in gleam deps

cf6018f

Generate app file for gleam deps on compilation

3ba141b

Proper beam compilation and .app file generation

6ed5fe7

Apply suggestions from code review

8123710

Co-authored-by: Eksperimental <eksperimental@autistici.org>

Add support for :application option in Compile.App

b75dc61

Papipo force-pushed the add-gleam-compiler branch from 9dde3f5 to b75dc61 Compare April 24, 2025 11:11

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Add gleam support to Mix #14262

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Add gleam support to Mix #14262

Are you sure you want to change the base?

Add gleam support to Mix #14262

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What is this?

What's missing?

Instructions

Usage

What needs to be tested?

Thanks

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