Fix API and IDE path with `/` relative_url_root

**Why?**
Previously we simply concatenated our paths, which led
to requesting `//api/v4/...` and obviously failed. The BE
supports a relative_url_root of `/`. It's a bug that the FE
does not.

1 files changed, 13 insertions, 1 deletions

diff --git a/spec/javascripts/api_spec.js b/spec/javascripts/api_spec.js
index e537e0e8afc..494b3b934a8 100644
--- a/spec/javascripts/api_spec.js
+++ b/spec/javascripts/api_spec.js
@@ -4,7 +4,7 @@ import Api from '~/api';
 
 describe('Api', () => {
   const dummyApiVersion = 'v3000';
-  const dummyUrlRoot = 'http://host.invalid';
+  const dummyUrlRoot = '/gitlab';
   const dummyGon = {
     api_version: dummyApiVersion,
     relative_url_root: dummyUrlRoot,
@@ -32,6 +32,18 @@ describe('Api', () => {
 
       expect(builtUrl).toEqual(expectedOutput);
     });
+
+    [null, '', '/'].forEach(root => {
+      it(`works when relative_url_root is ${root}`, () => {
+        window.gon.relative_url_root = root;
+        const input = '/api/:version/foo/bar';
+        const expectedOutput = `/api/${dummyApiVersion}/foo/bar`;
+
+        const builtUrl = Api.buildUrl(input);
+
+        expect(builtUrl).toEqual(expectedOutput);
+      });
+    });
   });
 
   describe('group', () => {