Cleaned up ForOf code (#260)

Perryvw · web-flow · commit c4cd09932bb1 · 2018-10-21T12:12:16.000+02:00
* Cleaned up forOf loop, made it use numeric loop instead of ipairs

* Fixed bug in non-array loop header and fixed tests

* Fixed up some PR comments
diff --git a/src/Transpiler.ts b/src/Transpiler.ts
@@ -558,28 +558,41 @@ export abstract class LuaTranspiler {
         const variable = (node.initializer as ts.VariableDeclarationList).declarations[0];
 
         // Transpile expression
-        const expression = this.transpileExpression(node.expression);
+        const iterable = this.transpileExpression(node.expression);
 
         // Use ipairs for array types, pairs otherwise
         const isArray = tsHelper.isArrayType(this.checker.getTypeAtLocation(node.expression), this.checker);
-        const pairs = isArray ? "ipairs" : "pairs";
 
-        // Make header
         let result = "";
-        if (ts.isIdentifier(variable.name)) {
-            result = this.indent + `for _, ${this.transpileIdentifier(variable.name)} in ${pairs}(${expression}) do\n`;
-        } else if (ts.isArrayBindingPattern(variable.name)) {
-            const valueVar =  "__forOfValue" + this.genVarCounter;
-            result = this.indent + `for _, ${valueVar} in ${pairs}(${expression}) do\n`;
-            const declaration = ts.createVariableDeclaration(variable.name, undefined, ts.createIdentifier(valueVar));
-            result += this.indent + this.transpileVariableDeclaration(declaration);
+
+        if (!isArray && ts.isIdentifier(variable.name)) {
+            result = this.indent + `for _, ${this.transpileIdentifier(variable.name)} in pairs(${iterable}) do\n`;
+        } else {
+            let itemVariable: ts.Identifier;
+            if (isArray) {
+                // Cache the expression result
+                result += this.indent + `local __loopVariable${this.genVarCounter} = ${iterable};\n`;
+                result += this.indent + `for i${this.genVarCounter}=1, #__loopVariable${this.genVarCounter} do\n`;
+                itemVariable = ts.createIdentifier(`__loopVariable${this.genVarCounter}[i${this.genVarCounter}]`);
+            } else {
+                const variableName = `__forOfValue${this.genVarCounter}`;
+                itemVariable =  ts.createIdentifier(variableName);
+                result += this.indent + `for _, ${variableName} in pairs(${iterable}) do\n`;
+            }
+
+            const declaration = ts.createVariableDeclaration(variable.name, undefined, itemVariable);
+            this.pushIndent();
+            result += this.indent + this.transpileVariableDeclaration(declaration) + ";\n";
+            this.popIndent();
         }
 
         // For body
         this.pushIndent();
         result += this.transpileLoopBody(node);
         this.popIndent();
 
+        this.genVarCounter++;
+
         return result + this.indent + "end\n";
     }
 
diff --git a/test/translation/lua/forOf.lua b/test/translation/lua/forOf.lua
@@ -1,4 +1,6 @@
-for _, i in ipairs({1,2,3,4,5,6,7,8,9,10}) do
+local __loopVariable0 = {1,2,3,4,5,6,7,8,9,10};
+for i0=1, #__loopVariable0 do
+    local i = __loopVariable0[i0];
     do
     end
     ::__continue0::
diff --git a/test/unit/loops.spec.ts b/test/unit/loops.spec.ts
@@ -286,6 +286,26 @@ export class LuaLoopTests {
         Expect(result).toBe(JSON.stringify(expected));
     }
 
+    @TestCase([[1, 2], [2, 3], [3, 4]], [3, 5, 7])
+    @Test("forof destructing")
+    public forofDestructing(inp: number[][], expected: any): void {
+        // Transpile
+        const lua = util.transpileString(
+            `let objTest = ${JSON.stringify(inp)};
+            let arrResultTest = [];
+            for (let [a,b] of objTest) {
+                arrResultTest.push(a + b)
+            }
+            return JSONStringify(arrResultTest);`
+        );
+
+        // Execute
+        const result = util.executeLua(lua);
+
+        // Assert
+        Expect(result).toBe(JSON.stringify(expected));
+    }
+
     @TestCase([0, 1, 2, 3, 4], [0, 0, 2, 0, 4])
     @Test("forof with continue")
     public forofWithContinue(inp: number[], expected: number[]): void {
