internal/ci: add libcue to PATH on Windows

Windows looks for DLLs in PATH, so add libcue to PATH.

GitHub actions don't allow setting PATH via `env`, rather we need
to append to the file pointed to by `$GITHUB_PATH`. Do this in a
separate step because this will only affect future steps.

This brings us one step closer to enabling CI on Windows, but we
don't do it in this CL yet as it requires additional work.

Updates cue-lang/cue#3253.

Signed-off-by: Aram Hăvărneanu <[email protected]>
Change-Id: I3f7e5d8acfed51961c3eaefd727ce76c3e08ae70
Reviewed-on: https://review.gerrithub.io/c/cue-lang/cue-py/+/1196833
Reviewed-by: Roger Peppe <[email protected]>
TryBot-Result: CUEcueckoo <[email protected]>

.github/workflows/trybot.yml

@@ -175,6 +175,9 @@ jobs:
         working-directory: libcue-checkout
       - name: mypy
         run: mypy .
+      - if: runner.os == 'Windows'
+        name: Add libcue to PATH
+        run: echo '${{ github.workspace }}/libcue-checkout' >> $GITHUB_PATH
       - name: pytest
         run: pytest
         env:

internal/ci/github/trybot.cue

@@ -82,6 +82,7 @@ workflows: trybot: _repo.bashWorkflow & {
 				_buildLibcue,
 
 				_mypy,
+				_addLibcueToPath,
 				_pytest,
 
 				_repo.checkGitClean,
@@ -102,7 +103,7 @@ workflows: trybot: _repo.bashWorkflow & {
 			"go-version": [_repo.latestStableGo]
 			"python-version": [_repo.latestStablePython]
 
-			// TODO: Windows doesn't work yet, see issue #3253
+            // TODO: Windows doesn't work yet, see issue #3253
 			runner: [_repo.linuxMachine, _repo.macosMachine]
 		}
 	}
@@ -152,6 +153,19 @@ workflows: trybot: _repo.bashWorkflow & {
 		run: "mypy ."
 	}
 
+	_addLibcueToPath: json.#step & {
+		name: "Add libcue to PATH"
+		if: "runner.os == 'Windows'"
+		// On Windows LoadLibrary loads DLLs from PATH. GitHub
+		// actions doesn't allow setting PATH via `env`,
+		// rather we need to append to the file pointed to by
+		// `$GITHUB_PATH`. This will only affect future steps,
+		// so we do it before running `pytest`.
+		run: """
+			echo '${{ github.workspace }}/libcue-checkout' >> $GITHUB_PATH
+			"""
+	}
+
 	_pytest: json.#step & {
 		name: "pytest"
 		env: LD_LIBRARY_PATH: "${{ github.workspace }}/libcue-checkout"