Always use forward slashes for python workers path handling

.changeset/young-vans-reply.md

@@ -0,0 +1,7 @@
+---
+"wrangler": patch
+---
+
+Fix Python Workers deployment failing on Windows due to path separator handling
+
+Previously, deploying Python Workers on Windows would fail because the backslash path separator (`\`) was not properly handled, causing the entire full path to be treated as a single filename. The deployment process now correctly normalizes paths to use forward slashes on all platforms.

packages/wrangler/src/__tests__/deploy.test.ts

@@ -13951,18 +13951,17 @@ export default{
 			const expectedModules = {
 				"index.py": mainPython,
 				"helper.py": "# Helper module\ndef helper(): pass",
-				[`python_modules${path.sep}module1.so`]: "binary content for module 1",
-				[`python_modules${path.sep}module2.py`]:
-					"# Python vendor module 2\nprint('hello')",
+				"python_modules/module1.so": "binary content for module 1",
+				"python_modules/module2.py": "# Python vendor module 2\nprint('hello')",
 			};
 
 			mockSubDomainRequest();
 			mockUploadWorkerRequest({
 				expectedMainModule: "index.py",
 				expectedModules,
 				excludedModules: [
-					`python_modules${path.sep}test.pyc`,
-					`python_modules${path.sep}other${path.sep}test.pyc`,
+					"python_modules/test.pyc",
+					"python_modules/other/test.pyc",
 				],
 			});
 

packages/wrangler/src/__tests__/find-additional-modules.test.ts

@@ -322,3 +322,68 @@ describe("traverse module graph", () => {
 		);
 	});
 });
+
+describe("Python modules", () => {
+	runInTempDir();
+	mockConsoleMethods();
+
+	it("should find python_modules with forward slashes (for cross-platform deploy)", async () => {
+		await mkdir("./python_modules/pkg/subpkg", { recursive: true });
+		await writeFile("./index.py", "def fetch(request): pass");
+		await writeFile("./python_modules/pkg/__init__.py", "");
+		await writeFile("./python_modules/pkg/subpkg/mod.py", "x = 1");
+
+		const modules = await findAdditionalModules(
+			{
+				file: path.join(process.cwd(), "./index.py"),
+				projectRoot: process.cwd(),
+				configPath: undefined,
+				format: "modules",
+				moduleRoot: process.cwd(),
+				exports: [],
+			},
+			[]
+		);
+
+		const pythonModules = modules.filter((m) =>
+			m.name.startsWith("python_modules/")
+		);
+		expect(pythonModules.map((m) => m.name)).toEqual(
+			expect.arrayContaining([
+				"python_modules/pkg/__init__.py",
+				"python_modules/pkg/subpkg/mod.py",
+			])
+		);
+		// This assertion catches Windows path.join() regression
+		pythonModules.forEach((m) => {
+			expect(m.name).not.toContain("\\");
+		});
+	});
+
+	it("should exclude files matching pythonModulesExcludes patterns", async () => {
+		await mkdir("./python_modules", { recursive: true });
+		await writeFile("./index.py", "def fetch(request): pass");
+		await writeFile("./python_modules/module.py", "x = 1");
+		await writeFile("./python_modules/module.pyc", "compiled");
+		await writeFile("./python_modules/test_module.py", "def test(): pass");
+
+		const modules = await findAdditionalModules(
+			{
+				file: path.join(process.cwd(), "./index.py"),
+				projectRoot: process.cwd(),
+				configPath: undefined,
+				format: "modules",
+				moduleRoot: process.cwd(),
+				exports: [],
+			},
+			[],
+			false,
+			["**/*.pyc", "**/test_*.py"]
+		);
+
+		const moduleNames = modules.map((m) => m.name);
+		expect(moduleNames).toContain("python_modules/module.py");
+		expect(moduleNames).not.toContain("python_modules/module.pyc");
+		expect(moduleNames).not.toContain("python_modules/test_module.py");
+	});
+});

packages/wrangler/src/deployment-bundle/find-additional-modules.ts

@@ -49,20 +49,28 @@ function isValidPythonPackageName(name: string): boolean {
 	return regex.test(name);
 }
 
+/**
+ * Checks if a given module name is a Python vendor module.
+ * @param moduleName The module name to check
+ */
+function isPythonVendorModule(moduleName: string): boolean {
+	// separator should be forward slash, as we always use forward slash for module names
+	// see `getFiles()` for more details
+	return moduleName.startsWith("python_modules/");
+}
+
 function removePythonVendorModules(
 	isPythonEntrypoint: boolean,
 	modules: CfModule[]
 ): CfModule[] {
 	if (!isPythonEntrypoint) {
 		return modules;
 	}
-	return modules.filter((m) => !m.name.startsWith("python_modules" + path.sep));
+	return modules.filter((m) => !isPythonVendorModule(m.name));
 }
 
 function getPythonVendorModulesSize(modules: CfModule[]): number {
-	const vendorModules = modules.filter((m) =>
-		m.name.startsWith("python_modules" + path.sep)
-	);
+	const vendorModules = modules.filter((m) => isPythonVendorModule(m.name));
 	return vendorModules.reduce((total, m) => total + m.content.length, 0);
 }
 
@@ -187,7 +195,10 @@ export async function findAdditionalModules(
 					return true; // Include this file
 				})
 				.map((m) => {
-					const prefixedPath = path.join("python_modules", m.name);
+					// Always use forward slashes for module names, regardless of platform.
+					// path.join() uses backslashes on Windows, but module names must use
+					// forward slashes for proper directory structure when deployed.
+					const prefixedPath = `python_modules/${m.name}`;
 					return {
 						...m,
 						name: prefixedPath,