TypeScriptToLua · Perryvw · May 28, 2022 · May 7, 2022 · May 7, 2022 · May 7, 2022
diff --git a/src/CompilerOptions.ts b/src/CompilerOptions.ts
@@ -29,6 +29,7 @@ export interface TypeScriptToLuaOptions {
     luaTarget?: LuaTarget;
     luaLibImport?: LuaLibImportKind;
     luaPlugins?: LuaPluginImport[];
+    noImplicitGlobalVariables?: boolean;
     noImplicitSelf?: boolean;
     noHeader?: boolean;
     noResolvePaths?: string[];

diff --git a/src/cli/parse.ts b/src/cli/parse.ts
@@ -58,6 +58,12 @@ export const optionDeclarations: CommandLineOption[] = [
         type: "enum",
         choices: Object.values(LuaTarget),
     },
+    {
+        name: "noImplicitGlobalVariables",
+        description:
+            'Specify to prevent implicitly turning "normal" variants into global variables in the transpiled output.',
+        type: "boolean",
+    },
     {
         name: "noImplicitSelf",
         description: 'If "this" is implicitly considered an any type, do not generate a self parameter.',

diff --git a/src/transformation/utils/lua-ast.ts b/src/transformation/utils/lua-ast.ts
@@ -137,6 +137,8 @@ export function createLocalOrExportedOrGlobalDeclaration(
     let declaration: lua.VariableDeclarationStatement | undefined;
     let assignment: lua.AssignmentStatement | undefined;
 
+    const noImplicitGlobalVariables = context.options.noImplicitGlobalVariables === true;
+
     const isFunctionDeclaration = tsOriginal !== undefined && ts.isFunctionDeclaration(tsOriginal);
 
     const identifiers = castArray(lhs);
@@ -160,7 +162,7 @@ export function createLocalOrExportedOrGlobalDeclaration(
         const scope = peekScope(context);
         const isTopLevelVariable = scope.type === ScopeType.File;
 
-        if (context.isModule || !isTopLevelVariable) {
+        if (context.isModule || !isTopLevelVariable || noImplicitGlobalVariables) {
             const isLuaFunctionExpression = rhs && !Array.isArray(rhs) && lua.isFunctionExpression(rhs);
             const isSafeRecursiveFunctionDeclaration = isFunctionDeclaration && isLuaFunctionExpression;
             if (!isSafeRecursiveFunctionDeclaration && hasMultipleReferences(scope, lhs)) {

diff --git a/test/unit/functions/noImplicitGlobalVariables.spec.ts b/test/unit/functions/noImplicitGlobalVariables.spec.ts
@@ -0,0 +1,30 @@
+import * as util from "../../util";
+
+test("normal TSTL creates global variables", () => {
+    const builder = util.testModule`
+        function foo() {}
+        const bar = 123;
+    `.expectToHaveNoDiagnostics();
+
+    const transpiledFile = builder.getLuaResult().transpiledFiles[0];
+    expect(transpiledFile).toBeDefined();
+    const { lua } = transpiledFile;
+    expect(lua).toBeDefined();
+    expect(lua).not.toContain("local");
+});
+
+test("noImplicitGlobalVariables does not create any global variables", () => {
+    const builder = util.testModule`
+        function foo() {}
+        const bar = 123;
+    `
+        .setOptions({ noImplicitGlobalVariables: true })
+        .expectToHaveNoDiagnostics();
+
+    const transpiledFile = builder.getLuaResult().transpiledFiles[0];
+    expect(transpiledFile).toBeDefined();
+    const { lua } = transpiledFile;
+    expect(lua).toBeDefined();
+    expect(lua).toContain("local function foo(");
+    expect(lua).toContain("local bar =");
+});