Formatting document fails in monorepo

[Minnozz]

Extension version: 1.7.6 (latest master)

The Format document feature uses the bsc.exe binary:

rescript-vscode/server/src/server.ts

Lines 740 to 742 in 877f874

	let projectRootPath = utils.findProjectRootOfFile(filePath);
	let bscBinaryPath =
	projectRootPath === null ? null : findBscBinary(projectRootPath);

The location of the bsc.exe binary is determined as follows:

rescript-vscode/server/src/server.ts

Lines 112 to 121 in 877f874

	let findBscBinary = (projectRootPath: p.DocumentUri) => {
	let rescriptBinaryPath = findRescriptBinary(projectRootPath);
	if (rescriptBinaryPath !== null) {
	let rescriptDirPath = path.join(
	path.dirname(rescriptBinaryPath),
	"..",
	"rescript"
	);
	let bscBinaryPath = path.join(rescriptDirPath, c.platformDir, c.bscExeName);

It is "reverse engineered" from the location of the rescript binary:

rescript-vscode/server/src/server.ts

Lines 107 to 110 in 877f874

	let findRescriptBinary = (projectRootPath: p.DocumentUri) =>
	extensionConfiguration.binaryPath == null
	? findBinaryPathFromProjectRoot(projectRootPath)
	: utils.findRescriptBinary(extensionConfiguration.binaryPath);

rescript-vscode/server/src/utils.ts

Lines 56 to 60 in 877f874

	export let findRescriptBinary = (
	binaryDirPath: p.DocumentUri | null
	): p.DocumentUri | null => {
	return findBinary(binaryDirPath, c.rescriptBinName);
	};

The node_modules/.bin/rescript symlink exists both at the monorepo top level node_modules and the subdir node_modules, which makes findRescriptBinary return src/monorepo/subdir/node_modules/.bin/rescript.

However, the node_modules/rescript directory usually exists only at the monorepo top level, so when the path of the rescript binary is used to derive the location of bsc.exe, this results in the non-existent path src/monorepo/subdir/node_modules/rescript/linux/bsc.exe. It should actually return src/monorepo/node_modules/rescript/linux/bsc.exe (without subdir).

To make things more complicated, if node_modules/rescript does exist in the subdir, that directory should be used. This may be the case when multiple rescript versions are used in the same monorepo.

[Minnozz]

I will create a PR that uses the correct algorithm for finding bsc.exe.

[Minnozz]

Note that a lot of the complexity comes from this guideline:

rescript-vscode/CONTRIBUTING.md

Line 159 in 877f874

- Do **not** directly use `node_modules/.bin/bsc` if you can help it. That's a Nodejs wrapper. Slow startup. We don't want our formatting to be momentarily stalled because some Nodejs cache went cold.

We want to use bsc.exe (ocaml binary) instead of bsc (nodejs wrapper). bsc lives in node_modules/.bin, while bsc.exe does not, so a different algorithm is needed.

[cristianoc]

See the forum discussion first.
Some agreement should be reached first.
Then documenting the agreement and implement it.
Turns out there are many opinions in what is a monorepo.

[Minnozz]

@cristianoc I think #573 may be a good candidate to merge even before consensus is reached about monorepos, because:

• Formatting worked in my monorepo in a previous version, and was broken recently
• This syncs the mechanism for finding bsc.exe to the mechanism for finding rescript, which is more logical
• It adds rescript.settings.platformPath, which can be used to fix formatting if you have a non-standard setup which is not automatically supported, while currently there is no easy way to fix formatting

[Freddy03h]

Hi, I'm on macos and I also got an issue about formatting on a monorepo (yarn v1 workspaces).

"format on save" or command "document format" don't format at all on a monorepo project (no issue on a normal project, with the exact same vs code config) with 1.6.0 version, I downgraded to 1.4.2 and it work.

[tsnobip]

We also have the same issue at work on our yarn v1 monorepo, it used to work fine before.