Error squiggles for Cargo.toml when build.rs requires environment variable

[cmazakas]

Even with a custom build command (and ctrl-shift-b succeeding), Cargo.toml still renders everything with red squiggles under everything telling me that the package failed to build, i.e.

failed to run custom build command for `cvrust v0.1.0 (C:\Users\...)`

My tasks.json is:

{
	"version": "2.0.0",
	"tasks": [
		{
			"type": "cargo",
			"subcommand": "build",
			"problemMatcher": [
				"$rustc"
			],
			"group": "build",
			"label": "Rust: cargo build - cvrust",
			"options": {
				"env": {
					"PNG_LIBRARY_DIR": "C:\\Users\\...
				}
			}
		}
	]
}

[rib]

I have the same problem because I need to set the FFMPEG_DIR environment variable for building ffmpeg-sys-next against pre-built ffmpeg libraries.

It feels like lots of people have been struggling with this limitation for many years but not getting any traction figuring out a good solution. E.g. some related issues I came across:

rust-lang/cargo#97
rust-lang/cargo#4121
rust-lang/rls#915
intellij-rust/intellij-rust#1569
rust-lang/rust-analyzer#6099
https://stackoverflow.com/questions/57017066/how-do-i-set-environment-variables-with-cargo

[cmazakas]

Yay, I'm not alone!

[rib]

For reference I've proposed one way that Cargo could ideally help here to avoid the need for configuring all the various IDEs to see the same environment.

rust-lang/cargo#4121 (comment)

The basic idea is that Cargo would check for an environment.json file (or something similar) at the top of your project which would let you configure environment variables for your project in one place and then it wouldn't matter if you're building via the command line or via vscode-rust/rust-analyzer/RLE etc in various different editors they would all see the same environment.