fix try/finally not re-throwing errors when there is no catch clause (#1667)

RealColdFry · RealColdFry · commit 9e25767d705b · 2026-03-18T19:32:31.000Z
When a try block had a finally but no catch, pcall's error result was
discarded, silently swallowing the exception. Now the error is captured
and re-thrown after the finally block executes.
diff --git a/src/transformation/visitors/errors.ts b/src/transformation/visitors/errors.ts
@@ -146,6 +146,10 @@ export const transformTryStatement: FunctionVisitor<ts.TryStatement> = (statemen
             returnedIdentifier,
             lua.SyntaxKind.AndOperator
         );
+    } else if (statement.finallyBlock) {
+        // try without catch, but with finally — need to capture error for re-throw
+        const errorIdentifier = lua.createIdentifier("____error");
+        result.push(lua.createVariableDeclarationStatement([tryResultIdentifier, errorIdentifier], tryCall));
     } else {
         // try without return or catch
         result.push(lua.createExpressionStatement(tryCall));
@@ -155,6 +159,22 @@ export const transformTryStatement: FunctionVisitor<ts.TryStatement> = (statemen
         result.push(...context.transformStatements(statement.finallyBlock));
     }
 
+    // Re-throw error if try had no catch but had a finally
+    if (!statement.catchClause && statement.finallyBlock) {
+        const notTryCondition = lua.createUnaryExpression(
+            lua.cloneIdentifier(tryResultIdentifier),
+            lua.SyntaxKind.NotOperator
+        );
+        const errorIdentifier = lua.createIdentifier("____error");
+        const rethrow = lua.createExpressionStatement(
+            lua.createCallExpression(lua.createIdentifier("error"), [
+                lua.cloneIdentifier(errorIdentifier),
+                lua.createNumericLiteral(0),
+            ])
+        );
+        result.push(lua.createIfStatement(notTryCondition, lua.createBlock([rethrow])));
+    }
+
     if (returnCondition && returnedIdentifier) {
         const returnValues: lua.Expression[] = [];
 
diff --git a/test/unit/error.spec.ts b/test/unit/error.spec.ts
@@ -256,6 +256,25 @@ test("multi return from catch->finally", () => {
         .expectToMatchJsResult();
 });
 
+test("throw propagates through finally to outer catch", () => {
+    util.testFunction`
+        function test() {
+            try {
+                throw "Test error";
+            } finally {
+            }
+        }
+
+        let result = 0;
+        try {
+            test();
+        } catch (e) {
+            result += 1;
+        }
+        return result;
+    `.expectToMatchJsResult();
+});
+
 test("return from nested finally", () => {
     util.testFunction`
         let x = "";
