add vars to global contexts (fix #259)

expr_sema.go

@@ -278,6 +278,8 @@ var BuiltinGlobalVariableTypes = map[string]ExprType{
 	// https://docs.github.com/en/actions/learn-github-actions/contexts#inputs-context
 	// https://docs.github.com/en/actions/learn-github-actions/reusing-workflows
 	"inputs": NewEmptyStrictObjectType(),
+	// https://docs.github.com/en/actions/learn-github-actions/contexts#vars-context
+	"vars": NewMapObjectType(StringType{}), // vars.<var_name>
 }
 
 // Semantics checker

testdata/ok/variables.yaml

@@ -0,0 +1,26 @@
+on:
+  workflow_dispatch:
+env:
+  # Setting an environment variable with the value of a configuration variable
+  env_var: ${{ vars.ENV_CONTEXT_VAR }}
+
+jobs:
+  display-variables:
+    name: ${{ vars.JOB_NAME }}
+    # You can use configuration variables with the `vars` context for dynamic jobs
+    if: ${{ vars.USE_VARIABLES == 'true' }}
+    runs-on: ${{ vars.RUNNER }}
+    environment: ${{ vars.ENVIRONMENT_STAGE }}
+    steps:
+      - name: Use variables
+        run: |
+          echo "repository variable : ${{ vars.REPOSITORY_VAR }}"
+          echo "organization variable : ${{ vars.ORGANIZATION_VAR }}"
+          echo "overridden variable : ${{ vars.OVERRIDE_VAR }}"
+          echo "variable from shell environment : $env_var"
+
+      - name: ${{ vars.HELLO_WORLD_STEP }}
+        if: ${{ vars.HELLO_WORLD_ENABLED == 'true' }}
+        uses: actions/hello-world-javascript-action@main
+        with:
+          who-to-greet: ${{ vars.GREET_NAME }}