feat: simple variable substitution support

fixes #565

src/utils/__tests__/openapi.test.ts

@@ -234,6 +234,24 @@ describe('Utils', () => {
       expect(res).toEqual([{ url: 'http://base.com/sandbox/test', description: '' }]);
     });
 
+    it('should correcly resolve url with server relative path', () => {
+      const res = normalizeServers('http://base.com/subpath/spec.yaml', [
+        {
+          url: '/sandbox/test',
+        },
+      ]);
+      expect(res).toEqual([{ url: 'http://base.com/sandbox/test', description: '' }]);
+    });
+
+    it('should correcly resolve url with relative path', () => {
+      const res = normalizeServers('http://base.com/subpath/spec.yaml', [
+        {
+          url: 'sandbox/test',
+        },
+      ]);
+      expect(res).toEqual([{ url: 'http://base.com/subpath/sandbox/test', description: '' }]);
+    });
+
     it('should prefer server host over spec`s one', () => {
       const res = normalizeServers('http://base.com/spec.yaml', [
         {
@@ -261,5 +279,35 @@ describe('Utils', () => {
       ]);
       expect(res).toEqual([{ url: 'https://base.com/sandbox/test', description: 'test' }]);
     });
+
+    it('should expand variables', () => {
+      const servers = normalizeServers('', [
+        {
+          url: '{protocol}{host}{basePath}',
+          variables: {
+            protocol: {
+              default: 'http://',
+            },
+            host: {
+              default: '127.0.0.1',
+            },
+            basePath: {
+              default: '/path/to/endpoint',
+            },
+          },
+        },
+        {
+          url: 'http://127.0.0.2:{port}',
+          variables: {},
+        },
+        {
+          url: 'http://127.0.0.3',
+        },
+      ]);
+
+      expect(servers[0].url).toEqual('http://127.0.0.1/path/to/endpoint');
+      expect(servers[1].url).toEqual('http://127.0.0.2:{port}');
+      expect(servers[2].url).toEqual('http://127.0.0.3');
+    });
   });
 });

src/utils/helpers.ts

@@ -1,4 +1,5 @@
 import slugify from 'slugify';
+import { format, parse } from 'url';
 
 /**
  * Maps over array passing `isLast` bool to iterator as the second arguemnt
@@ -133,3 +134,30 @@ export function safeSlugify(value: string): string {
       .replace(/-+$/, '')
   ); // Trim - from end of text
 }
+
+export function isAbsoluteUrl(url: string) {
+  return /(?:^[a-z][a-z0-9+.-]*:|\/\/)/i.test(url);
+}
+
+/**
+ * simple resolve URL which doesn't break on strings with url fragments
+ * e.g. resolveUrl('http://test.com:{port}', 'path') results in http://test.com:{port}/path
+ */
+export function resolveUrl(url: string, to: string) {
+  let res;
+  if (to.startsWith('//')) {
+    const { protocol: specProtocol } = parse(url);
+    res = `${specProtocol}${to}`;
+  } else if (isAbsoluteUrl(to)) {
+    res = to;
+  } else if (!to.startsWith('/')) {
+    res = stripTrailingSlash(url) + '/' + to;
+  } else {
+    const urlObj = parse(url);
+    res = format({
+      ...urlObj,
+      pathname: to,
+    });
+  }
+  return stripTrailingSlash(res);
+}

src/utils/openapi.ts

@@ -1,5 +1,4 @@
 import { dirname } from 'path';
-import { parse as urlParse, resolve as resolveUrl } from 'url';
 
 import { OpenAPIParser } from '../services/OpenAPIParser';
 import {
@@ -11,7 +10,7 @@ import {
   Referenced,
 } from '../types';
 import { IS_BROWSER } from './dom';
-import { isNumeric, stripTrailingSlash } from './helpers';
+import { isNumeric, resolveUrl } from './helpers';
 
 function isWildcardStatusCode(statusCode: string | number): statusCode is string {
   return typeof statusCode === 'string' && /\dxx/i.test(statusCode);
@@ -240,6 +239,13 @@ export function mergeSimilarMediaTypes(types: Dict<OpenAPIMediaType>): Dict<Open
   return mergedTypes;
 }
 
+function expandVariables(url: string, variables: object = {}) {
+  return url.replace(
+    /(?:{)(\w+)(?:})/g,
+    (match, name) => (variables[name] && variables[name].default) || match,
+  );
+}
+
 export function normalizeServers(
   specUrl: string | undefined,
   servers: OpenAPIServer[],
@@ -254,17 +260,16 @@ export function normalizeServers(
       },
     ];
   }
-  const { protocol: specProtocol } = urlParse(baseUrl);
 
-  function normalizeUrl(url: string): string {
-    url = resolveUrl(baseUrl, url);
-    return stripTrailingSlash(url.startsWith('//') ? `${specProtocol}${url}` : url);
+  function normalizeUrl(url: string, variables: object | undefined): string {
+    url = expandVariables(url, variables);
+    return resolveUrl(baseUrl, url);
   }
 
   return servers.map(server => {
     return {
       ...server,
-      url: normalizeUrl(server.url),
+      url: normalizeUrl(server.url, server.variables),
       description: server.description || '',
     };
   });