fix: try to use urllib4 (#177)

<!-- This is an auto-generated comment: release notes by coderabbit.ai
-->
## Summary by CodeRabbit

- **New Features**
- Introduced a conditional loading mechanism for the MockAgent and
related functions, enhancing flexibility with different urllib versions.
- **Style**
- Reformatted the dependencies array in the package.json for improved
readability.
- Added a newline at the end of the package.json for the server project.
<!-- end of auto-generated comment: release notes by coderabbit.ai -->

---------

Co-authored-by: coderabbitai[bot] <136622811+coderabbitai[bot]@users.noreply.github.com>

lib/mock_agent.js

@@ -1,5 +1,23 @@
 const { debuglog } = require('util');
-const { MockAgent, setGlobalDispatcher, getGlobalDispatcher } = require('urllib');
+let { MockAgent, setGlobalDispatcher, getGlobalDispatcher } = require('urllib');
+if (typeof getGlobalDispatcher === 'undefined') {
+  let urllibNext;
+  // https://github.com/eggjs/egg/blob/3.x/package.json#L59
+  try {
+    // try to use urllib4
+    urllibNext = require('urllib4');
+  } catch {
+    // try to use urllib-next
+    try {
+      urllibNext = require('urllib-next');
+    } catch {
+      throw new Error('Please install urllib@4');
+    }
+  }
+  MockAgent = urllibNext.MockAgent;
+  setGlobalDispatcher = urllibNext.setGlobalDispatcher;
+  getGlobalDispatcher = urllibNext.getGlobalDispatcher;
+}
 
 const debug = debuglog('egg-mock:lib:mock_agent');
 

test/fixtures/apps/no-framework/plugin/a/package.json

@@ -1,6 +1,8 @@
 {
   "eggPlugin": {
     "name": "a",
-    "dependencies": [ "egg-mock" ]
+    "dependencies": [
+      "egg-mock"
+    ]
   }
 }

test/fixtures/server/package.json

@@ -1,4 +1,4 @@
 {
   "name": "server",
   "version": "1.0.0"
-}
+}