Fix variable destructuring compatibility issue with lua 5.1 (#158)

Janne252 · Perryvw · commit bc073bb9d014 · 2018-07-28T13:43:51.000+02:00
* Fix variable destructuring compatibility issue for lua 5.1

* Remove deprecated assignmentDestructuring test files in favor of version-specific tests

* fix Lua 5.3 VM compatibility issue with running Lua 5.1 code

* Removed duplicate tests, renamed tests to match the test case

* Fix style &amp; coding conventions to match the project

* Remove unnecessary backport
(generated lualib no longer contains varible destruturing)
diff --git a/src/Transpiler.ts b/src/Transpiler.ts
@@ -1286,6 +1286,14 @@ export abstract class LuaTranspiler {
         return result;
     }
 
+    // Implemented in 5.1 and overridden in 5.2 (and onwards)
+    public transpileVariableDestructuring(value: string): string {
+        throw new TranspileError(
+            `transpileVariableDestructuring must be implemented!`,
+            null
+        );
+    }
+
     public transpileVariableDeclaration(node: ts.VariableDeclaration): string {
         if (ts.isIdentifier(node.name)) {
             // Find variable identifier
@@ -1298,20 +1306,20 @@ export abstract class LuaTranspiler {
             }
         } else if (ts.isArrayBindingPattern(node.name)) {
             // Destructuring type
-            const value = this.transpileExpression(node.initializer);
 
             // Disallow ellipsis destruction
             if (node.name.elements.some(elem => !ts.isBindingElement(elem) || elem.dotDotDotToken !== undefined)) {
                 throw new TranspileError(`Ellipsis destruction is not allowed.`, node);
             }
 
             const vars = node.name.elements.map(e => this.transpileArrayBindingElement(e)).join(",");
+            const value = this.transpileExpression(node.initializer);
 
             // Don't unpack TupleReturn decorated functions
             if (tsHelper.isTupleReturnCall(node.initializer, this.checker)) {
                 return `local ${vars}=${value}\n`;
             } else {
-                return `local ${vars}=table.unpack(${value})\n`;
+                return `local ${vars}=${this.transpileVariableDestructuring(value)}\n`;
             }
         } else {
             throw new TranspileError(
diff --git a/src/targets/Transpiler.51.ts b/src/targets/Transpiler.51.ts
@@ -4,5 +4,8 @@ import { TSHelper as tsHelper } from "../TSHelper";
 import * as ts from "typescript";
 
 export class LuaTranspiler51 extends LuaTranspiler {
-
+    /** @override */
+    public transpileVariableDestructuring(value: string): string {
+        return `unpack(${value})`;
+    }
 }
diff --git a/src/targets/Transpiler.52.ts b/src/targets/Transpiler.52.ts
@@ -53,4 +53,9 @@ export class LuaTranspiler52 extends LuaTranspiler51 {
                 return `bit32.arshift(${lhs},${rhs})`;
         }
     }
+
+    /** @override */
+    public transpileVariableDestructuring(value: string): string {
+        return `table.unpack(${value})`;
+    }
 }
diff --git a/test/translation/lua/assignmentDestructing.lua b/test/translation/lua/assignmentDestructing.lua
diff --git a/test/translation/ts/assignmentDestructing.ts b/test/translation/ts/assignmentDestructing.ts
diff --git a/test/unit/assignmentDestructuring.spec.ts b/test/unit/assignmentDestructuring.spec.ts
@@ -0,0 +1,30 @@
+import { Expect, Test, TestCase } from "alsatian";
+import { LuaTarget } from "../../src/Transpiler";
+import * as util from "../src/util";
+
+export class AssignmentDestructuringTests {
+
+    private readonly assignmentDestruturingTs = `
+        declare function myFunc(): [number, string];
+        let [a, b] = myFunc();`;
+
+    @Test("Assignment destructuring [5.1]")
+    public assignmentDestructuring51() {
+        // Transpile
+        const lua = util.transpileString(
+            this.assignmentDestruturingTs, {luaTarget: LuaTarget.Lua51, luaLibImport: "none"}
+        );
+        // Assert
+        Expect(lua).toBe(`local a,b=unpack(myFunc())`);
+    }
+
+    @Test("Assignment destructuring [5.2]")
+    public tupleDestructing52() {
+        // Transpile
+        const lua = util.transpileString(
+            this.assignmentDestruturingTs, {luaTarget: LuaTarget.Lua52, luaLibImport: "none"}
+        );
+        // Assert
+        Expect(lua).toBe(`local a,b=table.unpack(myFunc())`);
+    }
+}

Original file line number	Diff line number	Diff line change
`@@ -4,5 +4,8 @@ import { TSHelper as tsHelper } from "../TSHelper";`
`4`	`4`	`import * as ts from "typescript";`
`5`	`5`
`6`	`6`	`export class LuaTranspiler51 extends LuaTranspiler {`
`7`		`-`
	`7`	`+ /** @override */`
	`8`	`+ public transpileVariableDestructuring(value: string): string {`
	`9`	+ return `unpack(${value})`;
	`10`	`+ }`
`8`	`11`	`}`
Original file line number	Diff line number	Diff line change
`@@ -53,4 +53,9 @@ export class LuaTranspiler52 extends LuaTranspiler51 {`
`53`	`53`	return `bit32.arshift(${lhs},${rhs})`;
`54`	`54`	`}`
`55`	`55`	`}`
	`56`	`+`
	`57`	`+ /** @override */`
	`58`	`+ public transpileVariableDestructuring(value: string): string {`
	`59`	+ return `table.unpack(${value})`;
	`60`	`+ }`
`56`	`61`	`}`