fix: dont crash when an expression does not expand a matrix (#284)

src/audit/self_hosted_runner.rs

@@ -107,7 +107,9 @@ impl WorkflowAudit for SelfHostedRunner {
                 // The entire `runs-on:` is an expression, which may or may
                 // not be a self-hosted runner when expanded, like above.
                 LoE::Expr(exp) => {
-                    let matrix = Matrix::try_from(&job)?;
+                    let Ok(matrix) = Matrix::try_from(&job) else {
+                        continue;
+                    };
 
                     let expansions = matrix.expanded_values;
 

tests/snapshot.rs

@@ -192,6 +192,11 @@ fn self_hosted() -> Result<()> {
         .args(["--persona=auditor"])
         .run()?);
 
+    // Fixed regressions
+    insta::assert_snapshot!(zizmor()
+        .workflow(workflow_under_test("self-hosted/issue-283-repro.yml"))
+        .args(["--persona=auditor"])
+        .run()?);
     Ok(())
 }
 

tests/snapshots/snapshot__self_hosted-8.snap

@@ -0,0 +1,6 @@
+---
+source: tests/snapshot.rs
+expression: "zizmor().workflow(workflow_under_test(\"self-hosted/issue-283-repro.yml\")).args([\"--persona=auditor\"]).run()?"
+snapshot_kind: text
+---
+No findings to report. Good job!

tests/test-data/self-hosted/issue-283-repro.yml

@@ -0,0 +1,13 @@
+name: Workflow
+
+on:
+  workflow_call:
+    inputs:
+      os:
+        type: string
+
+jobs:
+  deploy:
+    runs-on: ${{inputs.os}}
+    steps:
+      - run: echo "Hello world"