ERR_INVALID_ARG_TYPE when running less task

[landlockedsurfer]

Hi!
I ran into an issue with sbt-less resulting in the following build error

[info] LESS compiling on 1 source(s)
[error] internal/fs/utils.js:701
[error]     throw new ERR_INVALID_ARG_TYPE(
[error]     ^
[error] 
[error] TypeError [ERR_INVALID_ARG_TYPE]: The "data" argument must be of type string or an instance of Buffer, TypedArray, or DataView. Received undefined
[error]     at Object.writeFile (fs.js:1385:5)
[error]     at /Users/landlockedsurfer/src/trash/sbt-less-example/project/target/less/lessc.js:89:20
[error]     at /Users/landlockedsurfer/src/trash/sbt-less-example/project/target/node-modules/webjars/mkdirp/index.js:47:26
[error]     at FSReqCallback.oncomplete (fs.js:177:5) {
[error]   code: 'ERR_INVALID_ARG_TYPE'
[error] }
...

The build error popped up yesterday all of a sudden (most likely due to a refresh of a node dependency).
After creating a standalone project I noticed that that issue seems to be related to files that are starting with the definition of a less variable.
I could not track down the cause of the problem but found a workaround by adding some additional lines at the top of the file.
E.g.
This file causes a build error

// /* add multiline comment to make things work, i.e. remove double slash at the start of this line */
// The problem seems to occur whenever the file starts with a variable declaration
@white: #fff;

By enabling the multiline comment at the start the less task runs fine again.

/* add multiline comment to make things work, i.e. remove double slash at the start of this line */
// The problem seems to occur whenever the file starts with a variable declaration
@white: #fff;

I've created a sample project to demonstrate the issue here: https://github.com/landlockedsurfer/sbt-less-test

Posting this workaround here in case someone else stumbles across this issue since I could not find anything in the internets.

[sbmpost]

might be related to newer version of node

[TheNorthMemory]

I've also got the similar error messages whose came from lessc.js:89:20.

sbt-less/src/main/resources/lessc.js

Lines 87 to 90 in 60a7e53

	mkdirp(path.dirname(sourceMapOutput), function (e) {
	throwIfErr(e);
	fs.writeFile(sourceMapOutput, content, "utf8", onDone);
	});

Checking the fs.writeFile((file, data[, options], callback)) manual, it was changed the behavior since v14.0.0 with:

The data parameter won't coerce unsupported input to strings anymore.

In L69, about the content, there was checked but L89 didn't. It should be undefined while less.sourceMap was turned as false or real empty(won't need). And then caused the fs.writeFile failed.

[mkurz]

Fixed by

• Write a sourcemap file when content is defined #116 (not merged)
• Bump sbt-web-build-base to 2.0.1. Fixes #118 #119 (cherry-picked the commit from mentioned pr)