TypeScriptToLua · RealColdFry · Apr 2, 2026 · Apr 2, 2026 · Apr 2, 2026 · Apr 2, 2026
diff --git a/benchmark/tsconfig.json b/benchmark/tsconfig.json
@@ -4,7 +4,7 @@
         "lib": ["esnext"],
         // Dev types are JIT
         "types": ["lua-types/jit", "@typescript-to-lua/language-extensions"],
-        "moduleResolution": "node",
+        "moduleResolution": "bundler",
         "outDir": "dist",
         "rootDir": "src",
         "strict": true,

diff --git a/eslint.config.mjs b/eslint.config.mjs
@@ -214,6 +214,7 @@ export default tseslint.config(
     {
         ignores: [
             ".github/scripts/create_benchmark_check.js",
+            "coverage/",
             "dist/",
             "eslint.config.mjs",
             "jest.config.js",

diff --git a/package-lock.json b/package-lock.json
diff --git a/package.json b/package.json
@@ -31,7 +31,7 @@
         "lint:prettier": "prettier --check . || (echo 'Run `npm run fix:prettier` to fix it.' && exit 1)",
         "lint:eslint": "eslint .",
         "fix:prettier": "prettier --write .",
-        "check:language-extensions": "tsc --strict language-extensions/index.d.ts",
+        "check:language-extensions": "tsc -p language-extensions/tsconfig.json",
         "preversion": "npm run build && npm test",
         "postversion": "git push && git push --tags"
     },
@@ -42,7 +42,7 @@
         "node": ">=16.10.0"
     },
     "peerDependencies": {
-        "typescript": "5.9.3"
+        "typescript": "6.0.2"
     },
     "dependencies": {
         "@typescript-to-lua/language-extensions": "1.19.0",
@@ -67,9 +67,12 @@
         "lua-types": "^2.14.1",
         "lua-wasm-bindings": "^0.5.3",
         "prettier": "^2.8.8",
-        "ts-jest": "^29.2.5",
+        "ts-jest": "^29.4.9",
         "ts-node": "^10.9.2",
-        "typescript": "5.9.3",
-        "typescript-eslint": "^8.46.3"
+        "typescript": "6.0.2",
+        "typescript-eslint": "^8.58.0"
+    },
+    "overrides": {
+        "typescript": "$typescript"
     }
 }
diff --git a/src/CompilerOptions.ts b/src/CompilerOptions.ts
@@ -99,8 +99,8 @@ export function validateOptions(options: CompilerOptions): ts.Diagnostic[] {
         diagnostics.push(diagnosticFactories.unsupportedJsxEmit());
     }
 
-    if (options.paths && !options.baseUrl) {
-        diagnostics.push(diagnosticFactories.pathsWithoutBaseUrl());
+    if (options.paths && Object.keys(options.paths).length > 0 && !options.baseUrl && !options.configFilePath) {
+        diagnostics.push(diagnosticFactories.pathsWithoutBaseDirectory());
     }
 
     return diagnostics;

diff --git a/src/transformation/utils/function-context.ts b/src/transformation/utils/function-context.ts
@@ -108,9 +108,7 @@ function computeDeclarationContextType(context: TransformationContext, signature
     const thisParameter = getExplicitThisParameter(signatureDeclaration);
     if (thisParameter) {
         // Explicit 'this'
-        return thisParameter.type && thisParameter.type.kind === ts.SyntaxKind.VoidKeyword
-            ? ContextType.Void
-            : ContextType.NonVoid;
+        return thisParameter.type?.kind === ts.SyntaxKind.VoidKeyword ? ContextType.Void : ContextType.NonVoid;
     }
 
     // noSelf declaration on function signature

diff --git a/src/transformation/visitors/variable-declaration.ts b/src/transformation/visitors/variable-declaration.ts
@@ -62,7 +62,7 @@ export function transformBindingPattern(
         }
 
         // Build the path to the table
-        const tableExpression = propertyAccessStack.reduce<lua.Expression>(
+        const tableExpression = propertyAccessStack.reduce(
             (path, property) => lua.createTableIndexExpression(path, transformPropertyName(context, property)),
             table
         );

diff --git a/src/transpilation/diagnostics.ts b/src/transpilation/diagnostics.ts
@@ -56,8 +56,9 @@ export const cannotBundleLibrary = createDiagnosticFactory(
 
 export const unsupportedJsxEmit = createDiagnosticFactory(() => 'JSX is only supported with "react" jsx option.');
 
-export const pathsWithoutBaseUrl = createDiagnosticFactory(
-    () => "When configuring 'paths' in tsconfig.json, the option 'baseUrl' must also be provided."
+export const pathsWithoutBaseDirectory = createDiagnosticFactory(
+    () =>
+        "When using 'paths' without 'baseUrl', a tsconfig.json must be present so paths can be resolved relative to it."
 );
 
 export const emitPathCollision = createDiagnosticFactory(

diff --git a/src/transpilation/resolve.ts b/src/transpilation/resolve.ts
@@ -10,7 +10,7 @@ import { couldNotReadDependency, couldNotResolveRequire } from "./diagnostics";
 import { BuildMode, CompilerOptions } from "../CompilerOptions";
 import { findLuaRequires, LuaRequire } from "./find-lua-requires";
 import { Plugin } from "./plugins";
-import * as picomatch from "picomatch";
+import picomatch from "picomatch";
 
 const resolver = resolve.ResolverFactory.createResolver({
     extensions: [".lua"],
@@ -28,6 +28,7 @@ interface ResolutionResult {
 
 class ResolutionContext {
     private noResolvePaths: picomatch.Matcher[];
+    private pathsBase: string | undefined;
 
     public diagnostics: ts.Diagnostic[] = [];
     public resolvedFiles = new Map<string, ProcessedFile>();
@@ -39,8 +40,8 @@ class ResolutionContext {
         private readonly plugins: Plugin[]
     ) {
         const unique = [...new Set(options.noResolvePaths)];
-        const matchers = unique.map(x => picomatch(x));
-        this.noResolvePaths = matchers;
+        this.noResolvePaths = unique.map(x => picomatch(x));
+        this.pathsBase = options.baseUrl ?? (options.configFilePath ? path.dirname(options.configFilePath) : undefined);
     }
 
     public addAndResolveDependencies(file: ProcessedFile): void {
@@ -210,21 +211,18 @@ class ResolutionContext {
             if (resolvedNodeModulesFile) return resolvedNodeModulesFile;
         }
 
+        // Bare specifiers: check paths mappings first, matching TypeScript's resolution order.
+        // TS never applies paths to relative imports, so skip for those.
+        if (!ts.isExternalModuleNameRelative(dependencyPath) && this.options.paths && this.pathsBase) {
+            const fileFromPaths = this.tryGetModuleNameFromPaths(dependencyPath, this.options.paths, this.pathsBase);
+            if (fileFromPaths) return fileFromPaths;
+        }
+
         // Check if file is a file in the project
         const resolvedPath = this.formatPathToFile(dependencyPath, requiringFile);
         const fileFromPath = this.getFileFromPath(resolvedPath);
         if (fileFromPath) return fileFromPath;
 
-        if (this.options.paths && this.options.baseUrl) {
-            // If no file found yet and paths are present, try to find project file via paths mappings
-            const fileFromPaths = this.tryGetModuleNameFromPaths(
-                dependencyPath,
-                this.options.paths,
-                this.options.baseUrl
-            );
-            if (fileFromPaths) return fileFromPaths;
-        }
-
         // Not a TS file in our project sources, use resolver to check if we can find dependency
         try {
             const resolveResult = resolver.resolveSync({}, fileDirectory, dependencyPath);

diff --git a/src/utils.ts b/src/utils.ts
@@ -77,7 +77,7 @@ export function cast<TOriginal, TCast extends TOriginal>(
 }
 
 export function assert(value: any, message?: string | Error): asserts value {
-    nativeAssert(value, message);
+    nativeAssert.ok(value, message);
 }
 
 export function assertNever(_value: never): never {

diff --git a/test/setup.ts b/test/setup.ts
@@ -13,7 +13,7 @@ declare global {
 
 expect.extend({
     toHaveDiagnostics(diagnostics: ts.Diagnostic[], expected?: number[]): jest.CustomMatcherResult {
-        assert(Array.isArray(diagnostics));
+        assert.ok(Array.isArray(diagnostics));
         // @ts-ignore
         const matcherHint = this.utils.matcherHint("toHaveDiagnostics", undefined, "", this);
 

diff --git a/test/transpile/__snapshots__/module-resolution.spec.ts.snap b/test/transpile/__snapshots__/module-resolution.spec.ts.snap
@@ -10,8 +10,8 @@ exports[`supports complicated paths configuration 1`] = `
 
 exports[`supports paths configuration 1`] = `
 [
-  "/paths-simple/myprogram/dist/main.lua",
   "/paths-simple/myprogram/dist/mypackage/bar.lua",
   "/paths-simple/myprogram/dist/mypackage/index.lua",
+  "/paths-simple/myprogram/dist/myprogram/main.lua",
 ]
 `;
diff --git a/test/transpile/module-resolution.spec.ts b/test/transpile/module-resolution.spec.ts
@@ -4,7 +4,6 @@ import * as util from "../util";
 import * as ts from "typescript";
 import { BuildMode } from "../../src";
 import { normalizeSlashes } from "../../src/utils";
-import { pathsWithoutBaseUrl } from "../../src/transpilation/diagnostics";
 
 describe("basic module resolution", () => {
     const projectPath = path.resolve(__dirname, "module-resolution", "project-with-node-modules");
@@ -471,6 +470,8 @@ describe("module resolution should not try to resolve modules in noResolvePaths"
                     export function foo(): void;
                 }`
             )
+            // TS 6.0 noUncheckedSideEffectImports requires declaration for "preload" module
+            .addExtraFile("preload.d.ts", `declare module "preload" {}`)
             .setOptions({ noResolvePaths: ["ignore*"] })
             .expectToHaveNoDiagnostics()
             .expectToEqual({ result: "foo" });
@@ -598,7 +599,7 @@ test("module resolution uses baseURL to resolve imported files", () => {
                 return { baz = function() return "baz" end }
             `
         )
-        .setOptions({ baseUrl: "./myproject/mydeps" })
+        .setOptions({ baseUrl: "./myproject/mydeps", ignoreDeprecations: "6.0" })
         .expectToEqual({
             fooResult: "foo",
             barResult: "bar",
@@ -707,8 +708,21 @@ test("supports complicated paths configuration", () => {
         .expectToEqual({ foo: 314, bar: 271 });
 });
 
-test("paths without baseUrl is error", () => {
-    util.testFunction``.setOptions({ paths: {} }).expectToHaveDiagnostics([pathsWithoutBaseUrl.code]);
+test("paths without baseUrl is not an error", () => {
+    util.testFunction``.setOptions({ paths: {} }).expectToHaveNoDiagnostics();
+});
+
+test("supports paths configuration without baseUrl", () => {
+    const baseProjectPath = path.resolve(__dirname, "module-resolution", "paths-no-baseurl");
+    const projectPath = path.join(baseProjectPath, "myprogram");
+    const projectTsConfig = path.join(projectPath, "tsconfig.json");
+    const mainFile = path.join(projectPath, "main.ts");
+
+    // Bundle to have all files required to execute and check result
+    util.testProject(projectTsConfig)
+        .setMainFileName(mainFile)
+        .setOptions({ luaBundle: "bundle.lua", luaBundleEntry: mainFile })
+        .expectToEqual({ foo: 314, bar: 271 });
 });
 
 test("module resolution using plugin", () => {

diff --git a/test/transpile/module-resolution/paths-base-tsconfig/tsconfig.base.json b/test/transpile/module-resolution/paths-base-tsconfig/tsconfig.base.json
@@ -2,6 +2,7 @@
     "compilerOptions": {
         "rootDir": ".",
         "baseUrl": ".",
+        "ignoreDeprecations": "6.0",
         "paths": {
             "mypackage": ["packages/mypackage/src/index.ts"],
             "mypackage/*": ["packages/mypackage/src/*"]

diff --git a/test/transpile/module-resolution/paths-no-baseurl/mypackage/bar.ts b/test/transpile/module-resolution/paths-no-baseurl/mypackage/bar.ts
@@ -0,0 +1 @@
+export const bar = 271;
diff --git a/test/transpile/module-resolution/paths-no-baseurl/mypackage/index.ts b/test/transpile/module-resolution/paths-no-baseurl/mypackage/index.ts
@@ -0,0 +1 @@
+export const foo = 314;
diff --git a/test/transpile/module-resolution/paths-no-baseurl/myprogram/main.ts b/test/transpile/module-resolution/paths-no-baseurl/myprogram/main.ts
@@ -0,0 +1,4 @@
+import { foo } from "myOtherPackage";
+import { bar } from "myOtherPackage/bar";
+
+export { foo, bar };
diff --git a/test/transpile/module-resolution/paths-no-baseurl/myprogram/tsconfig.json b/test/transpile/module-resolution/paths-no-baseurl/myprogram/tsconfig.json
@@ -0,0 +1,10 @@
+{
+    "compilerOptions": {
+        "rootDir": "..",
+        "outDir": "dist",
+        "paths": {
+            "myOtherPackage": ["../mypackage"],
+            "myOtherPackage/*": ["../mypackage/*"]
+        }
+    }
+}
diff --git a/test/transpile/module-resolution/paths-simple/myprogram/tsconfig.json b/test/transpile/module-resolution/paths-simple/myprogram/tsconfig.json
@@ -1,6 +1,8 @@
 {
     "compilerOptions": {
         "baseUrl": ".",
+        "ignoreDeprecations": "6.0",
+        "rootDir": "..",
         "outDir": "dist",
         "paths": {
             "myOtherPackage": ["../mypackage"],

diff --git a/test/transpile/module-resolution/project-with-complicated-dependency/tsconfig.json b/test/transpile/module-resolution/project-with-complicated-dependency/tsconfig.json
@@ -1,7 +1,7 @@
 {
     "compilerOptions": {
         "strict": true,
-        "moduleResolution": "Node",
+        "moduleResolution": "Bundler",
         "target": "esnext",
         "lib": ["esnext"],
         "types": [],

diff --git a/test/transpile/module-resolution/project-with-dependency-chain/tsconfig.json b/test/transpile/module-resolution/project-with-dependency-chain/tsconfig.json
@@ -1,7 +1,7 @@
 {
     "compilerOptions": {
         "strict": true,
-        "moduleResolution": "Node",
+        "moduleResolution": "Bundler",
         "target": "esnext",
         "lib": ["esnext"],
         "types": [],

diff --git a/test/transpile/module-resolution/project-with-node-modules/tsconfig.json b/test/transpile/module-resolution/project-with-node-modules/tsconfig.json
@@ -1,12 +1,13 @@
 {
     "compilerOptions": {
         "strict": true,
-        "moduleResolution": "Node",
+        "moduleResolution": "Bundler",
         "noUnusedLocals": true,
         "noUnusedParameters": true,
         "target": "esnext",
         "lib": ["esnext"],
         "types": [],
-        "rootDir": "."
+        "rootDir": ".",
+        "noUncheckedSideEffectImports": false
     }
 }
diff --git a/test/transpile/module-resolution/project-with-sourceDir/tsconfig.json b/test/transpile/module-resolution/project-with-sourceDir/tsconfig.json
@@ -1,7 +1,7 @@
 {
     "compilerOptions": {
         "strict": true,
-        "moduleResolution": "Node",
+        "moduleResolution": "Bundler",
         "target": "esnext",
         "lib": ["esnext"],
         "types": [],

diff --git a/test/transpile/transformers/fixtures.ts b/test/transpile/transformers/fixtures.ts
@@ -36,7 +36,7 @@ export const compilerOptions =
     (options: tstl.CompilerOptions): ts.TransformerFactory<ts.SourceFile> =>
     context =>
     file => {
-        assert(options.plugins?.length === 1);
+        assert.ok(options.plugins?.length === 1);
         return visitAndReplace(context, file, node => {
             if (!ts.isReturnStatement(node)) return;
             return ts.factory.updateReturnStatement(node, ts.factory.createTrue());

diff --git a/test/tsconfig.json b/test/tsconfig.json
@@ -2,8 +2,7 @@
     "extends": "../tsconfig.json",
     "compilerOptions": {
         "rootDir": "..",
-        "types": ["node", "jest"],
-        "baseUrl": "."
+        "types": ["node", "jest"]
     },
     "include": [".", "../src"],
     "exclude": [

diff --git a/test/unit/__snapshots__/identifiers.spec.ts.snap b/test/unit/__snapshots__/identifiers.spec.ts.snap
@@ -52,18 +52,14 @@ exports[`ambient identifier must be a valid lua identifier ("enum $$ {}"): code
 
 exports[`ambient identifier must be a valid lua identifier ("enum $$ {}"): diagnostics 1`] = `"main.ts(3,9): error TSTL: Invalid ambient identifier name '$$$'. Ambient identifiers must be valid lua identifiers."`;
 
-exports[`ambient identifier must be a valid lua identifier ("function $$();"): code 1`] = `"local ____ = _____24_24_24"`;
+exports[`ambient identifier must be a valid lua identifier ("function $$(): void;"): code 1`] = `"local ____ = _____24_24_24"`;
 
-exports[`ambient identifier must be a valid lua identifier ("function $$();"): diagnostics 1`] = `"main.ts(3,9): error TSTL: Invalid ambient identifier name '$$$'. Ambient identifiers must be valid lua identifiers."`;
+exports[`ambient identifier must be a valid lua identifier ("function $$(): void;"): diagnostics 1`] = `"main.ts(3,9): error TSTL: Invalid ambient identifier name '$$$'. Ambient identifiers must be valid lua identifiers."`;
 
 exports[`ambient identifier must be a valid lua identifier ("let $$: any;"): code 1`] = `"local ____ = _____24_24_24"`;
 
 exports[`ambient identifier must be a valid lua identifier ("let $$: any;"): diagnostics 1`] = `"main.ts(3,9): error TSTL: Invalid ambient identifier name '$$$'. Ambient identifiers must be valid lua identifiers."`;
 
-exports[`ambient identifier must be a valid lua identifier ("module $$ { export const bar: any; }"): code 1`] = `"local ____ = _____24_24_24"`;
-
-exports[`ambient identifier must be a valid lua identifier ("module $$ { export const bar: any; }"): diagnostics 1`] = `"main.ts(3,9): error TSTL: Invalid ambient identifier name '$$$'. Ambient identifiers must be valid lua identifiers."`;
-
 exports[`ambient identifier must be a valid lua identifier ("namespace $$ { export const bar: any; }"): code 1`] = `"local ____ = _____24_24_24"`;
 
 exports[`ambient identifier must be a valid lua identifier ("namespace $$ { export const bar: any; }"): diagnostics 1`] = `"main.ts(3,9): error TSTL: Invalid ambient identifier name '$$$'. Ambient identifiers must be valid lua identifiers."`;

diff --git a/test/unit/annotations/customConstructor.spec.ts b/test/unit/annotations/customConstructor.spec.ts
@@ -11,8 +11,8 @@ test("CustomCreate", () => {
     const tsHeader = `
         /** @customConstructor Point2DCreate */
         class Point2D {
-            public x: number;
-            public y: number;
+            public x!: number;
+            public y!: number;
             constructor(x: number, y: number) {
                 // No values assigned
             }

diff --git a/test/unit/assignments.spec.ts b/test/unit/assignments.spec.ts
@@ -342,7 +342,7 @@ test.each([
 
 test("local variable declaration referencing self indirectly", () => {
     util.testFunction`
-        let cb: () => void;
+        let cb!: () => void;
 
         function foo(newCb: () => void) {
             cb = newCb;
@@ -360,7 +360,7 @@ test("local variable declaration referencing self indirectly", () => {
 
 test("local multiple variable declaration referencing self indirectly", () => {
     util.testFunction`
-        let cb: () => void;
+        let cb!: () => void;
 
         function foo(newCb: () => void) {
             cb = newCb;
@@ -395,7 +395,7 @@ describe.each(["x &&= y", "x ||= y"])("boolean compound assignment (%p)", assign
 
 test.each([undefined, 3])("nullish coalescing compound assignment", initialValue => {
     util.testFunction`
-        let x: number = ${util.formatCode(initialValue)};
+        let x: number | undefined = ${util.formatCode(initialValue)};
         x ??= 5;
         return x;
     `.expectToMatchJsResult();