fix: process mutated env by plugins in dev server

src/utils/run-build.ts

@@ -1,6 +1,8 @@
 import { promises as fs } from 'fs'
 import path, { join } from 'path'
 
+import { NetlifyConfig } from '@netlify/build'
+
 import BaseCommand from '../commands/base-command.js'
 import { $TSFixMe } from '../commands/types.js'
 import { getBootstrapURL } from '../lib/edge-functions/bootstrap.js'
@@ -87,7 +89,7 @@ export const runNetlifyBuild = async ({
     edgeFunctionsBootstrapURL: await getBootstrapURL(),
   }
 
-  const devCommand = async (settingsOverrides = {}) => {
+  const devCommand = async ({ netlifyConfig, settingsOverrides }: { netlifyConfig?: NetlifyConfig; settingsOverrides?: Partial<ServerSettings> } = {}) => {
     let cwd = command.workingDir
 
     if (!options.cwd && command.project.workspace?.packages.length) {
@@ -99,6 +101,11 @@ export const runNetlifyBuild = async ({
         ...settings,
         ...settingsOverrides,
         ...(options.skipWaitPort ? { skipWaitPort: true } : {}),
+        env: {
+          ...settings.env,
+          ...settingsOverrides?.env,
+          ...netlifyConfig?.build.environment
+        }
       },
       cwd,
     })
@@ -140,7 +147,7 @@ export const runNetlifyBuild = async ({
     if (!options.dir && netlifyConfig?.build?.publish) {
       settingsOverrides.dist = netlifyConfig.build.publish
     }
-    await devCommand(settingsOverrides)
+    await devCommand({ netlifyConfig, settingsOverrides })
 
     return { configPath: tempConfigPath }
   }

tests/integration/commands/dev/dev.test.ts

@@ -730,6 +730,59 @@ describe.concurrent('command/dev', () => {
           )
         })
       })
+
+      test('ensures dev server plugins can mutate env', async (t) => {
+        await withSiteBuilder(t, async (builder) => {
+          await builder
+            .withNetlifyToml({
+              config: {
+                plugins: [{ package: './plugins/plugin' }],
+                dev: {
+                  command: 'node index.mjs',
+                  targetPort: 4444
+                },
+              },
+            })
+            .withBuildPlugin({
+              name: 'plugin',
+              plugin: {
+                async onPreDev({ netlifyConfig }) {
+                  netlifyConfig.build.environment.SOME_ENV = 'value'
+                },
+              },
+            })
+            .withContentFile({
+              path: 'index.mjs',
+              content: `
+              import process from 'process';
+              import http from 'http';
+
+              const server = http.createServer((req, res) => {
+                res.write(process.env.SOME_ENV)
+                res.end();
+              })
+
+              server.listen(4444)
+              `,
+            })
+            .build()
+
+          await withDevServer(
+            {
+              cwd: builder.directory,
+            },
+            async (server) => {
+              const output = server.outputBuffer.map((buff) => buff.toString()).join('\n')
+              t.expect(output).toContain('Netlify configuration property "build.environment.SOME_ENV" value changed.')
+              t.expect(output).toContain('Server now ready')
+
+              const res = await fetch(new URL('/', server.url))
+              t.expect(res.status).toBe(200)
+              t.expect(await res.text()).toBe('value')
+            },
+          )
+        })
+      })
     })
   })
 })