fix: make path merging more forgiving and add tests

src/__tests__/combinePaths.test.ts

@@ -1,17 +1,31 @@
 import { combinePaths } from "../combinePaths";
 
-it("merges two simple paths correctly", () => {
-	expect(combinePaths("subpath", "/basepath/").pathname).toEqual(
-		"/basepath/subpath"
-	);
-});
+const testPaths: [paths: [base: string, sub: string], expected: string][] = [
+	// adds leading and trailing slash to basepath
+	[["basepath", "subpath"], "/basepath/subpath"],
+
+	// drops leading slash on subpath
+	[["/basepath/", "/subpath"], "/basepath/subpath"],
+
+	// preserves trailing slash on subpath
+	[["/basepath/", "subpath/"], "/basepath/subpath/"],
+];
 
-it("drops the basepath if subpath has a leading slash", () => {
-	expect(combinePaths("/subpath", "/basepath/").pathname).toEqual("/subpath");
+it("matches testPaths results", () => {
+	testPaths.forEach((testConfig) => {
+		const [paths, expected] = testConfig;
+		expect(combinePaths(paths[1], paths[0]).pathname).toEqual(expected);
+	});
 });
 
 it("preserves search params from both subpath and basepath", () => {
 	expect(
 		combinePaths("subpath?subParam=1", "/basepath/?baseParam=2").search
 	).toEqual("?subParam=1&baseParam=2");
 });
+
+it("preserves the hash from only the subpath", () => {
+	expect(
+		combinePaths("subpath?subParam=1#testHash", "/basepath#ignoredHash").hash
+	).toEqual("#testHash");
+});

src/__tests__/defineRoute.test.ts

@@ -0,0 +1,24 @@
+import { defineRoute } from "../defineRoute";
+
+const testParams = {
+	paramA: "1234",
+	paramB: "4567",
+};
+
+const testConfig = (params: typeof testParams) =>
+	`/base/sub/${params.paramA}/${params.paramB}?query=8910#hash`;
+
+it("templates route property correctly", () => {
+	// Query and hash should be dropped, and paramProxy should properly template the params
+	expect(defineRoute(testConfig).route).toEqual("/base/sub/:paramA/:paramB");
+});
+
+it("extends a base route properly", () => {
+	const route = defineRoute(testConfig).extend(
+		(params: { paramC: string }) => `/extended/${params.paramC}`
+	);
+
+	expect(route.link({ ...testParams, paramC: "1121" })).toEqual(
+		`/base/sub/${testParams.paramA}/${testParams.paramB}/extended/1121?query=8910`
+	);
+});

src/combinePaths.ts

@@ -1,7 +1,12 @@
+import { addTrailingSlash, removeLeadingSlash } from "./pathUtils";
+
 export const combinePaths = (path: string, basePath: string): URL => {
 	const baseUrl = new URL(basePath, window.location.origin);
 
-	const url = new URL(path, baseUrl);
+	baseUrl.pathname = addTrailingSlash(baseUrl.pathname);
+
+	const url = new URL(removeLeadingSlash(path), baseUrl);
+
 	baseUrl.searchParams.forEach((value, key) => {
 		url.searchParams.set(key, value);
 	});

src/pathUtils.ts

@@ -0,0 +1,5 @@
+export const addTrailingSlash = (s: string): string =>
+	s.charAt(s.length - 1) === "/" ? s : s + "/";
+
+export const removeLeadingSlash = (s: string): string =>
+	s.charAt(0) === "/" ? s.slice(1) : s;