fix: remove trailing slash for invalid URL

src/util/url-template.ts

@@ -156,7 +156,7 @@ export function parseUrl(template: string) {
 function expand(template: string, context: object): string {
   var operators = ["+", "#", ".", "/", ";", "?", "&"];
 
-  return template.replace(
+  template = template.replace(
     /\{([^\{\}]+)\}|([^\{\}]+)/g,
     function (_, expression, literal) {
       if (expression) {
@@ -190,4 +190,10 @@ function expand(template: string, context: object): string {
       }
     },
   );
+
+  if (template === "/") {
+    return template;
+  } else {
+    return template.replace(/\/$/, "");
+  }
 }

test/endpoint.test.ts

@@ -336,7 +336,7 @@ describe("endpoint()", () => {
     expect(endpoint("/").url).toEqual("https://api.github.com/");
     expect(endpoint("/").method).toEqual("GET");
     expect(endpoint("https://github.acme-inc/api/v3/").url).toEqual(
-      "https://github.acme-inc/api/v3/",
+      "https://github.acme-inc/api/v3",
     );
   });
 
@@ -500,6 +500,36 @@ describe("endpoint()", () => {
     });
   });
 
+  it("Undefined placeholder value with no trailing slash in URL", () => {
+    const options1 = endpoint("GET /repos/{owner}/{repo}/branches/{branch}", {
+      owner: "owner",
+      repo: "repo",
+    });
+
+    expect(options1).toEqual({
+      method: "GET",
+      url: "https://api.github.com/repos/owner/repo/branches",
+      headers: {
+        accept: "application/vnd.github.v3+json",
+        "user-agent": userAgent,
+      },
+    });
+
+    const options2 = endpoint("GET /repos/{owner}/{repo}/branches{/branch}", {
+      owner: "owner",
+      repo: "repo",
+    });
+
+    expect(options2).toEqual({
+      method: "GET",
+      url: "https://api.github.com/repos/owner/repo/branches",
+      headers: {
+        accept: "application/vnd.github.v3+json",
+        "user-agent": userAgent,
+      },
+    });
+  });
+
   it("Undefined header value", () => {
     const options = endpoint({
       method: "GET",