fix(buildUrl): relative url is invalid URL (OAS3) or non-url (OAS2) (#6864)

* OAS3: relative url when no servers defined AND specUrl is invalid Url

* OAS2: specUrl is non-url string

test/unit/core/utils.js

@@ -39,6 +39,7 @@ import {
 } from "core/utils/url"
 
 import win from "core/window"
+import { afterAll, beforeAll, expect, jest } from "@jest/globals"
 
 describe("utils", () => {
 
@@ -1389,6 +1390,17 @@ describe("utils", () => {
   })
 
   describe("buildUrl", () => {
+    const { location } = window
+    beforeAll(() => {
+      delete window.location
+      window.location = {
+        href: "http://localhost/",
+      }
+    })
+    afterAll(() => {
+      window.location = location
+    })
+
     const specUrl = "https://petstore.swagger.io/v2/swagger.json"
 
     const noUrl = ""
@@ -1401,6 +1413,9 @@ describe("utils", () => {
     const serverUrlRelativeToBase = "server-example/base-path/path"
     const serverUrlRelativeToHost = "/server-example/base-path/path"
 
+    const specUrlAsInvalidUrl = "./examples/test.yaml"
+    const specUrlOas2NonUrlString = "an allowed OAS2 TermsOfService description string"
+
     it("build no url", () => {
       expect(buildUrl(noUrl, specUrl, { selectedServer: absoluteServerUrl })).toBe(undefined)
       expect(buildUrl(noUrl, specUrl, { selectedServer: serverUrlRelativeToBase })).toBe(undefined)
@@ -1432,6 +1447,14 @@ describe("utils", () => {
       expect(buildUrl(urlRelativeToBase, specUrl, { selectedServer: serverUrlRelativeToHost })).toBe("https://petstore.swagger.io/server-example/base-path/relative-url/base-path/path")
       expect(buildUrl(urlRelativeToHost, specUrl, { selectedServer: serverUrlRelativeToHost })).toBe("https://petstore.swagger.io/relative-url/base-path/path")
     })
+
+    it("build relative url when no servers defined AND specUrl is invalid Url", () => {
+      expect(buildUrl(urlRelativeToHost, specUrlAsInvalidUrl, { selectedServer: noServerSelected })).toBe("http://localhost/relative-url/base-path/path")
+    })
+
+    it("build relative url when no servers defined AND specUrl is OAS2 non-url string", () => {
+      expect(buildUrl(urlRelativeToHost, specUrlOas2NonUrlString, { selectedServer: noServerSelected })).toBe("http://localhost/relative-url/base-path/path")
+    })
   })
 
   describe("requiresValidationURL", () => {