`hh compile` fails without detailed error message if `/tmp/hardhat-solc` is not writable

[KartikSoneji]

Version of Hardhat

3.0.0-next.29

What happened?

npx hardhat compile fails with a nondescriptive error message if /tmp/hardhat-solc is not writable.

The spawnCompile() function creates the folder, resulting it being owned by the current user.
If another user attempts compilation while the folder exists, it throws an error.

hardhat/v-next/hardhat/src/internal/builtin-plugins/solidity/build-system/compiler/compiler.ts

Lines 50 to 58 in 58a9598

	async function spawnCompile(
	command: string,
	args: string[],
	input: CompilerInput,
	): Promise<CompilerOutput> {
	// We create a temporary folder to store the output of the compiler in
	// We use a random UUID to avoid collisions with other compilations
	const tmpFolder = path.join(os.tmpdir(), "hardhat-solc", crypto.randomUUID());
	await mkdir(tmpFolder);

mkdir() by default does create folders with mode 777, but since the default umask is 022, it results in a folder with 755
(nodejs/node#15092)
This can be fixed by explicitly using chmod() to set the permission after creation.

Minimal reproduction steps

On a system that has more than one user:

1. compile project as user a

   sudo su user-a
   npx hardhat compile

2. switch to user b

   sudo su user-b

3. attempt to compile project as user b

   $ npx hardhat compile
   Compiling your Solidity contracts...
   Error HHE907: A native version of solc failed to run.
   
   If you are running MacOS, try installing Apple Rosetta.
   
   If this error persists, run "npx hardhat clean --global".

Search terms

compile error, /tmp/hardhat-solc not writable

[fvictorio]

Hey @KartikSoneji, thanks a lot for the detailed issue description, this was super interesting.

The way I see it, the fix is to either chmod the created directory to have 777 permissions, or to use /tmp/hardhat-solc-{uuid} instead of /tmp/hardhat-solc/{uuid}.

[michalbrabec]

Possible solutions:

• Create /tmp/hardhat-solc/ with writing permissions for everyone. I'm pretty sure this works and shouldn't have any security implications, but it makes me feel a bit nervous anyway.
• Create /tmp/hardhat-solc-{uuid} instead of /tmp/hardhat-solc/{uuid}. That way each workdir is independent and this problem doesn't happen.
• Stop using /tmp altogether. Using that directory has given us headaches in the past, so maybe we should always use the project's /cache directory (or /cache/tmp maybe?)

We selected option 2
We will migrate to option 3 as part of #7219