Add CI workflow to run CN1 Playground language smoke tests

.github/workflows/cn1playground-language.yml

@@ -0,0 +1,47 @@
+name: CN1 Playground Language Tests
+
+on:
+  pull_request:
+    types: [opened, synchronize, reopened, ready_for_review]
+    paths:
+      - 'scripts/cn1playground/**'
+      - '.github/workflows/cn1playground-language.yml'
+  push:
+    branches: [main, master]
+    paths:
+      - 'scripts/cn1playground/**'
+      - '.github/workflows/cn1playground-language.yml'
+  workflow_dispatch:
+
+permissions:
+  contents: read
+
+jobs:
+  language-smoke:
+    name: Playground language smoke
+    runs-on: ubuntu-latest
+
+    steps:
+      - name: Check out repository
+        uses: actions/checkout@v4
+
+      - name: Set up Java 17
+        uses: actions/setup-java@v4
+        with:
+          distribution: temurin
+          java-version: '17'
+          cache: maven
+
+      - name: Ensure Xvfb is available
+        run: |
+          set -euo pipefail
+          if ! command -v xvfb-run >/dev/null 2>&1; then
+            sudo apt-get update
+            sudo apt-get install -y xvfb
+          fi
+
+      - name: Run playground language smoke tests
+        run: |
+          set -euo pipefail
+          cd scripts/cn1playground
+          xvfb-run -a bash tools/run-playground-smoke-tests.sh

scripts/cn1playground/README.md

@@ -347,9 +347,37 @@ mvn clean install
 
 ```bash
 cd scripts/cn1playground
-./scripts/run-tests.sh
+bash tools/run-playground-smoke-tests.sh
 ```
 
+This smoke command currently runs:
+
+1. CN1 access registry generation (`tools/generate-cn1-access-registry.sh`).
+2. Registry sanity checks (expected/forbidden class entries).
+3. `PlaygroundSmokeHarness` end-to-end behavior checks.
+4. `PlaygroundSyntaxMatrixHarness` syntax regression checks.
+
+## Language Feature Rollout Process
+
+Use this process when adding or fixing Java syntax support in Playground:
+
+1. **Add/adjust matrix coverage first**  
+   Update `common/src/test/java/com/codenameone/playground/PlaygroundSyntaxMatrixHarness.java` with a focused snippet for the target syntax.
+   - For currently unsupported syntax, add as `ExpectedOutcome.FAILURE`.
+   - When support lands, flip that case to `ExpectedOutcome.SUCCESS`.
+
+2. **Implement parser/runtime change in small steps**  
+   Prefer one syntax feature per PR (e.g. method references only) to keep regressions easy to isolate.
+
+3. **Run smoke + syntax matrix locally**  
+   Run `bash tools/run-playground-smoke-tests.sh` from `scripts/cn1playground`.
+
+4. **Require CI green before merge**  
+   The `CN1 Playground Language Tests` workflow runs the same smoke command under CI (`xvfb-run`) and should pass before merging syntax updates.
+
+5. **Document behavior changes**  
+   Update this README's known issues/limitations when syntax support changes so users know what is now supported.
+
 ## Known Issues
 
 1. **Parse errors with complex expressions**: BeanShell's parser may fail on some Java syntax. Simplify complex expressions or break them into multiple statements.
@@ -360,4 +388,4 @@ cd scripts/cn1playground
 
 ## Contributing
 
-See the main Codename One repository for contribution guidelines.
+See the main Codename One repository for contribution guidelines.

scripts/cn1playground/common/src/main/java/bsh/BSHEnhancedForStatement.java

@@ -67,6 +67,9 @@ public Object eval(CallStack callstack, Interpreter interpreter) throws EvalErro
             statement = nodeCount > 1 ? jjtGetChild(1) : null;
         }
         final Object iteratee = expression.eval(callstack, interpreter);
+        if (iteratee == null || iteratee == Primitive.NULL) {
+            throw new EvalException("Cannot iterate over null value", this, callstack);
+        }
         final CollectionManager cm = CollectionManager.getCollectionManager();
         final Iterator<?> iterator = cm.getBshIterator(iteratee);
         try {