Fix context failed to be resolved due to parentheses (#1095)

* Fix context failed to be resolved due to parentheses

* Added test with more parentheses

Author: Perryvw

src/transpilation/transformers.ts

@@ -36,6 +36,7 @@ export function getTransformers(
 
             ...(transformersFromOptions.after ?? []),
             ...(customTransformers.after ?? []),
+            stripParenthesisExpressionsTransformer,
             luaTransformer,
         ],
     };
@@ -53,6 +54,30 @@ export const noImplicitSelfTransformer: ts.TransformerFactory<ts.SourceFile | ts
         : transformSourceFile(node);
 };
 
+export const stripParenthesisExpressionsTransformer: ts.TransformerFactory<ts.SourceFile> = context => sourceFile => {
+    // Remove parenthesis expressions before transforming to Lua, so transpiler is not hindered by extra ParenthesizedExpression nodes
+    function unwrapParentheses(node: ts.Expression) {
+        while (ts.isParenthesizedExpression(node)) {
+            node = node.expression;
+        }
+        return node;
+    }
+    function visit(node: ts.Node): ts.Node {
+        // For now only call expressions strip their expressions of parentheses, there could be more cases where this is required
+        if (ts.isCallExpression(node)) {
+            return ts.factory.updateCallExpression(
+                node,
+                unwrapParentheses(node.expression),
+                node.typeArguments,
+                node.arguments
+            );
+        }
+
+        return ts.visitEachChild(node, visit, context);
+    }
+    return ts.visitNode(sourceFile, visit);
+};
+
 function loadTransformersFromOptions(program: ts.Program, diagnostics: ts.Diagnostic[]): ts.CustomTransformers {
     const customTransformers: Required<ts.CustomTransformers> = {
         before: [],

test/unit/classes/classes.spec.ts

@@ -761,3 +761,41 @@ test("constructor class name available with constructor", () => {
         .setReturnExport("className")
         .expectToEqual("MyClass");
 });
+
+// https://github.com/TypeScriptToLua/TypeScriptToLua/issues/959
+test("methods accessed via this index pass correct context", () => {
+    util.testModule`
+        class Example {
+            baz = 3;
+            foo() {
+                this["bar"]()
+            }
+
+            bar() {
+                return this.baz;
+            }
+        }
+
+        const inst = new Example();
+        export const result = inst.foo();
+    `.expectToMatchJsResult();
+});
+
+// https://github.com/TypeScriptToLua/TypeScriptToLua/issues/959
+test.each(['(this["bar"])', '((((this["bar"]))))'])("methods in parentheses pass correct context %s", callPath => {
+    util.testModule`
+        class Example {
+            baz = 3;
+            foo() {
+                ${callPath}()
+            }
+
+            bar() {
+                return this.baz;
+            }
+        }
+
+        const inst = new Example();
+        export const result = inst.foo();
+    `.expectToMatchJsResult();
+});