replace dots with underscores in output paths instead of expanding to nested directories

RealColdFry · RealColdFry · commit 3f30817a57f1 · 2026-04-03T02:45:56.000+01:00
diff --git a/src/transpilation/diagnostics.ts b/src/transpilation/diagnostics.ts
@@ -63,5 +63,5 @@ export const pathsWithoutBaseUrl = createDiagnosticFactory(
 export const emitPathCollision = createDiagnosticFactory(
     (outputPath: string, file1: string, file2: string) =>
         `Output path '${outputPath}' is used by both '${file1}' and '${file2}'. ` +
-        `Dots in file/directory names are expanded to nested directories for Lua module resolution.`
+        `Dots in file/directory names are replaced with underscores for Lua module resolution.`
 );
diff --git a/src/transpilation/transpiler.ts b/src/transpilation/transpiler.ts
@@ -144,7 +144,6 @@ export class Transpiler {
             diagnostics.push(...bundleDiagnostics);
             emitPlan = [bundleFile];
         } else {
-            // Check for output path collisions caused by dot expansion
             const outputPathMap = new Map<string, string>();
             emitPlan = resolutionResult.resolvedFiles.map(file => {
                 const outputPath = getEmitPath(file.fileName, program);
@@ -198,13 +197,12 @@ export function getEmitPathRelativeToOutDir(fileName: string, program: ts.Progra
         emitPathSplits[0] = "lua_modules";
     }
 
-    // Expand dots in path segments into nested directories so that Lua's require()
-    // resolves correctly (e.g. "Foo.Bar/index.ts" -> "Foo/Bar/index.lua").
-    // Dots are path separators in Lua's module system, so a file at "Foo.Bar/index.lua"
-    // would be unreachable via require("Foo.Bar.index") since Lua looks for "Foo/Bar/index.lua".
-    // Strip the source extension first, split all dots, then re-add the output extension.
+    // Replace dots with underscores in path segments so that Lua's require()
+    // resolves correctly. Dots are path separators in Lua's module system, so
+    // "Foo.Bar/index.lua" would be unreachable via require("Foo.Bar.index")
+    // since Lua interprets it as "Foo/Bar/index.lua".
     emitPathSplits[emitPathSplits.length - 1] = trimExtension(emitPathSplits[emitPathSplits.length - 1]);
-    emitPathSplits = emitPathSplits.flatMap(segment => segment.split("."));
+    emitPathSplits = emitPathSplits.map(segment => segment.replace(/\./g, "_"));
 
     // Set extension
     const extension = ((program.getCompilerOptions() as CompilerOptions).extension ?? "lua").trim();
diff --git a/test/unit/modules/resolution.spec.ts b/test/unit/modules/resolution.spec.ts
@@ -1,3 +1,4 @@
+import * as path from "path";
 import * as ts from "typescript";
 import { couldNotResolveRequire, emitPathCollision } from "../../../src/transpilation/diagnostics";
 import * as util from "../../util";
@@ -170,8 +171,7 @@ test.each([
 // Can't test this via execution because the test harness uses package.preload
 // instead of real filesystem resolution, so require() always finds the module
 // regardless of output path. We check the output path directly instead.
-// TODO: test via actual Lua execution once the harness supports filesystem resolution.
-test("dots in directory names emit to nested directories", () => {
+test("dots in directory names are replaced with underscores in output", () => {
     const { transpiledFiles } = util.testModule`
         import { answer } from "./Foo.Bar";
         export const result = answer;
@@ -180,21 +180,20 @@ test("dots in directory names emit to nested directories", () => {
         .setOptions({ rootDir: "." })
         .getLuaResult();
 
-    // Foo.Bar/index.ts should emit to Foo/Bar/index.lua, not Foo.Bar/index.lua
     const dottedFile = transpiledFiles.find(f => f.lua?.includes("answer = 42"));
     expect(dottedFile).toBeDefined();
-    expect(dottedFile!.outPath).toContain("Foo/Bar/index.lua");
+    expect(dottedFile!.outPath).toContain(path.join("Foo_Bar", "index.lua"));
     expect(dottedFile!.outPath).not.toContain("Foo.Bar");
 });
 
 test("dots in paths that collide with existing paths produce a diagnostic", () => {
     util.testModule`
         import { a } from "./Foo.Bar";
-        import { b } from "./Foo/Bar";
+        import { b } from "./Foo_Bar";
         export const result = a + b;
     `
         .addExtraFile("Foo.Bar/index.ts", "export const a = 1;")
-        .addExtraFile("Foo/Bar/index.ts", "export const b = 2;")
+        .addExtraFile("Foo_Bar/index.ts", "export const b = 2;")
         .setOptions({ rootDir: "." })
         .expectToHaveDiagnostics([emitPathCollision.code]);
 });
