chore: test: exercise contexts in matrix when validating workflows (#1033)

After realizing my mistake on my proposed fixes in #1028, I figured I could at least propose another test covering the use of contexts in `jobs.<job-id>.strategy.matrix`.

The specification for available contexts is [here](https://docs.github.com/en/actions/reference/workflows-and-actions/contexts#context-availability):

| Workflow key | Context |
| -------------------- | ----------- |
| `jobs.<job_id>.strategy` | `github`, `needs`, `vars`, `inputs` |

In Forgejo, the `forge` and `forgejo` contexts are supported in addition to `github`.

The new test covers a matrix with [`include`](https://docs.github.com/en/actions/reference/workflows-and-actions/workflow-syntax#jobsjob_idstrategymatrixinclude), [`exclude`](https://docs.github.com/en/actions/reference/workflows-and-actions/workflow-syntax#jobsjob_idstrategymatrixexclude) and custom properties. Both available and unavailable contexts are tested.

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  - [PR](https://code.forgejo.org/forgejo/runner/pulls/1033): <!--number 1033 --><!--line 0 --><!--description Y2hvcmU6IHRlc3Q6IGV4ZXJjaXNlIGNvbnRleHRzIGluIG1hdHJpeCB3aGVuIHZhbGlkYXRpbmcgd29ya2Zsb3dz-->chore: test: exercise contexts in matrix when validating workflows<!--description-->
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Co-authored-by: 2franix <code@c.defx.fr>
Reviewed-on: https://code.forgejo.org/forgejo/runner/pulls/1033
Reviewed-by: earl-warren <earl-warren@noreply.code.forgejo.org>
Co-authored-by: 2franix <2franix@noreply.code.forgejo.org>
Co-committed-by: 2franix <2franix@noreply.code.forgejo.org>

act/schema/schema_test.go

@@ -30,6 +30,84 @@ jobs:
 	assert.NoError(t, err)
 }
 
+func TestContextsInWorkflowMatrix(t *testing.T) {
+	t.Run("KnownContexts", func(t *testing.T) {
+		// Parse raw YAML snippet.
+		var node yaml.Node
+		err := yaml.Unmarshal([]byte(`
+on: push
+
+jobs:
+  job:
+    uses: ./.forgejo/workflow/test.yaml
+    strategy:
+      matrix:
+        input1:
+          - ${{ forge.KEY }}
+          - ${{ forgejo.KEY }}
+          - ${{ github.KEY }}
+          - ${{ inputs.KEY }}
+          - ${{ vars.KEY }}
+          - ${{ needs.KEY }}
+        include:
+         - forge: ${{ forge.KEY }}
+         - forgejo: ${{ forgejo.KEY }}
+         - github: ${{ github.KEY }}
+         - inputs: ${{ inputs.KEY }}
+         - vars: ${{ vars.KEY }}
+         - needs: ${{ needs.KEY }}
+        exclude:
+         - forge: ${{ forge.KEY }}
+         - forgejo: ${{ forgejo.KEY }}
+         - github: ${{ github.KEY }}
+         - inputs: ${{ inputs.KEY }}
+         - vars: ${{ vars.KEY }}
+         - needs: ${{ needs.KEY }}
+`), &node)
+		if !assert.NoError(t, err) {
+			return
+		}
+
+		// Parse YAML node as a validated workflow.
+		err = (&Node{
+			Definition: "workflow-root",
+			Schema:     GetWorkflowSchema(),
+		}).UnmarshalYAML(&node)
+		assert.NoError(t, err)
+	})
+
+	t.Run("UnknownContext", func(t *testing.T) {
+		for _, property := range []string{"include", "exclude", "input1"} {
+			t.Run(property, func(t *testing.T) {
+				for _, context := range []string{"secrets", "job", "steps", "runner", "matrix", "strategy"} {
+					t.Run(context, func(t *testing.T) {
+						var node yaml.Node
+						err := yaml.Unmarshal([]byte(fmt.Sprintf(`
+on: push
+
+jobs:
+  job:
+    uses: ./.forgejo/workflow/test.yaml
+    strategy:
+      matrix:
+        %[1]s:
+          - input1: ${{ %[2]s.KEY }}
+`, property, context)), &node)
+						if !assert.NoError(t, err) {
+							return
+						}
+						err = (&Node{
+							Definition: "workflow-root",
+							Schema:     GetWorkflowSchema(),
+						}).UnmarshalYAML(&node)
+						assert.ErrorContains(t, err, "Unknown Variable Access "+context)
+					})
+				}
+			})
+		}
+	})
+}
+
 func TestReusableWorkflow(t *testing.T) {
 	t.Run("KnownContexts", func(t *testing.T) {
 		var node yaml.Node