Fix try/catch/finally flow

SuperPaintman · SuperPaintman · commit 523849964b2b · 2026-06-28T05:43:02.000+01:00
Closes: #1137
diff --git a/src/transformation/visitors/errors.ts b/src/transformation/visitors/errors.ts
@@ -165,6 +165,7 @@ export const transformTryStatement: FunctionVisitor<ts.TryStatement> = (statemen
 
     const tryResultIdentifier = lua.createIdentifier("____try");
     const returnValueIdentifier = lua.createIdentifier("____returnValue");
+    const rethrowIdentifier = lua.createIdentifier("____rethrow");
 
     const result: lua.Statement[] = [];
 
@@ -191,20 +192,36 @@ export const transformTryStatement: FunctionVisitor<ts.TryStatement> = (statemen
             }
         }
         result.push(lua.createVariableDeclarationStatement(tryReturnIdentifiers, tryCall));
+        if (statement.finallyBlock) {
+            result.push(lua.createVariableDeclarationStatement(rethrowIdentifier));
+        }
 
         const catchCall = lua.createCallExpression(
             catchIdentifier,
             statement.catchClause.variableDeclaration ? [lua.cloneIdentifier(returnedIdentifier)] : []
         );
         const catchCallStatement = hasReturn
             ? lua.createAssignmentStatement(
-                  [lua.cloneIdentifier(returnedIdentifier), lua.cloneIdentifier(returnValueIdentifier)],
-                  catchCall
-              )
+                [lua.cloneIdentifier(returnedIdentifier), lua.cloneIdentifier(returnValueIdentifier)],
+                catchCall
+            )
             : lua.createExpressionStatement(catchCall);
 
+        const catchCallFunction = lua.createFunctionExpression(lua.createBlock([catchCallStatement]));
+
+        const tryCatchCall = lua.createCallExpression(pCall, [catchCallFunction]);
+
+        const tryCatchCallStatement = lua.createAssignmentStatement(
+            [lua.cloneIdentifier(tryResultIdentifier), lua.cloneIdentifier(rethrowIdentifier)],
+            tryCatchCall
+        );
+
         const notTryCondition = lua.createUnaryExpression(tryResultIdentifier, lua.SyntaxKind.NotOperator);
-        result.push(lua.createIfStatement(notTryCondition, lua.createBlock([catchCallStatement])));
+        result.push(lua.createIfStatement(notTryCondition, lua.createBlock(
+            statement.finallyBlock
+                ? [tryCatchCallStatement]
+                : [catchCallStatement]
+        )));
     } else if (tryScope.functionReturned) {
         // try with return, but no catch
         // returnedIdentifier = lua.createIdentifier("____returned");
@@ -230,21 +247,31 @@ 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.
+    // Re-throw error if try had a finally.
     // On pcall failure the error is the second return value, which lands in
-    // ____hasReturned (when functionReturned) or ____error (otherwise).
-    if (!statement.catchClause && statement.finallyBlock) {
+    // ____hasReturned (when functionReturned), ____rethrow
+    // (catch throw/re-throw), or ____error (otherwise).
+    if (statement.finallyBlock) {
         const notTryCondition = lua.createUnaryExpression(
             lua.cloneIdentifier(tryResultIdentifier),
             lua.SyntaxKind.NotOperator
         );
-        const errorIdentifier = tryScope.functionReturned
-            ? lua.cloneIdentifier(returnedIdentifier)
-            : lua.createIdentifier("____error");
-        const rethrow = lua.createExpressionStatement(
-            lua.createCallExpression(lua.createIdentifier("error"), [errorIdentifier, lua.createNumericLiteral(0)])
-        );
-        result.push(lua.createIfStatement(notTryCondition, lua.createBlock([rethrow])));
+
+        if (!statement.catchClause) {
+            const errorIdentifier = tryScope.functionReturned
+                ? lua.cloneIdentifier(returnedIdentifier)
+                : lua.createIdentifier("____error");
+            const rethrow = lua.createExpressionStatement(
+                lua.createCallExpression(lua.createIdentifier("error"), [errorIdentifier, lua.createNumericLiteral(0)])
+            );
+            result.push(lua.createIfStatement(notTryCondition, lua.createBlock([rethrow])));
+        } else if (statement.catchClause.block.statements.length > 0) {
+            // Re-throw is possible only from non-empty blocks.
+            const rethrow = lua.createExpressionStatement(
+                lua.createCallExpression(lua.createIdentifier("error"), [rethrowIdentifier, lua.createNumericLiteral(0)])
+            );
+            result.push(lua.createIfStatement(notTryCondition, lua.createBlock([rethrow])));
+        }
     }
 
     if (returnCondition && returnedIdentifier) {
diff --git a/test/unit/error.spec.ts b/test/unit/error.spec.ts
@@ -7,31 +7,40 @@ test("throwString", () => {
     `.expectToEqual(new util.ExecutionError("Some Error"));
 });
 
-// TODO: Finally does not behave like it should, see #1137
-// eslint-disable-next-line jest/no-disabled-tests
-test.skip.each([0, 1, 2])("re-throw (%p)", i => {
+test.each([
+    { innerTry: false, innerFinally: false, outerFinally: false },
+    { innerTry: false, innerFinally: false, outerFinally: true },
+    { innerTry: false, innerFinally: true, outerFinally: false },
+    { innerTry: false, innerFinally: true, outerFinally: true },
+    { innerTry: true, innerFinally: false, outerFinally: false },
+    { innerTry: true, innerFinally: false, outerFinally: true },
+    { innerTry: true, innerFinally: true, outerFinally: false },
+    { innerTry: true, innerFinally: true, outerFinally: true },
+])("re-throw (%j)", o => {
     util.testFunction`
-        const i: number = ${i};
+        const innerTry: boolean = ${o.innerTry};
+        const innerFinally: boolean = ${o.innerFinally};
+        const outerFinally: boolean = ${o.outerFinally};
         function foo() {
             try {
                 try {
-                    if (i === 0) { throw "z"; }
+                    if (innerTry) { throw "inner.try"; }
                 } catch (e) {
-                    throw "a";
+                    throw (e as string) + "->" + "inner.catch";
                 } finally {
-                    if (i === 1) { throw "b"; }
+                    if (innerFinally) { throw "inner.finally"; }
                 }
             } catch (e) {
-                throw (e as string).toUpperCase();
+                throw (e as string) + "->" + "outer.catch";
             } finally {
-                throw "C";
+                if (outerFinally) { throw "outer.finally"; }
             }
         }
         let result: string = "x";
         try {
             foo();
         } catch (e) {
-            result = (e as string)[(e as string).length - 1];
+            result = e as string;
         }
         return result;
     `.expectToMatchJsResult();
