Add support for phases within the next config object

Author: cyrilwanner

README.md

@@ -153,6 +153,17 @@ module.exports = withPlugins([
 ], nextConfig);
 ```
 
+Phases are also supported within the `nextConfiguration` object and have the same syntax as in [plugin `configuration` objects](#configuration-object).
+```javascript
+const { PHASE_DEVELOPMENT_SERVER } = require('next-server/constants');
+const nextConfig = {
+  distDir: 'build',
+  ['!' + PHASE_DEVELOPMENT_SERVER]: {
+    assetPrefix: 'https://my.cdn.com',
+  },
+};
+```
+
 ### Optional plugins
 
 If a plugin should only get loaded when it is used, you can use the `optional` helper function.

src/__tests__/index.test.js

@@ -101,4 +101,28 @@ describe('next-compose-plugins', () => {
     expect(plugin1).toHaveBeenCalledTimes(1);
     expect(plugin2).toHaveBeenCalledTimes(1);
   });
+
+  it('resolves phases specific configs in the next configuration', () => {
+    const baseConfig = withPlugins([], {
+      baseConfig: 'hello',
+      foo: 'bar',
+      [PHASE_DEVELOPMENT_SERVER]: {
+        foo: 'baz',
+      },
+      [`!${PHASE_PRODUCTION_SERVER}`]: {
+        prod: false,
+      },
+      [`!${PHASE_DEVELOPMENT_SERVER}`]: {
+        dev: false,
+      },
+    });
+
+    const result = baseConfig(PHASE_DEVELOPMENT_SERVER, {});
+
+    expect(result).toEqual({
+      baseConfig: 'hello',
+      foo: 'baz',
+      prod: false,
+    });
+  });
 });

src/compose.js

@@ -58,7 +58,7 @@ export const composePlugins = (phase, plugins, initialConfig) => {
     nextComposePlugins: true,
     phase,
   };
-  let config = { ...initialConfig };
+  let config = mergePhaseConfiguration(phase, { ...initialConfig });
 
   plugins.forEach((plugin) => {
     const { pluginFunction, pluginConfig, phases } = parsePluginConfig(plugin);