feat: emit system log when plugin has failed to load

packages/build/src/core/build.ts

@@ -618,6 +618,8 @@ const runBuild = async function ({
     debug,
     verbose,
     netlifyConfig,
+    featureFlags,
+    systemLog,
   })
 
   const { steps, events } =

packages/build/src/core/feature_flags.ts

@@ -22,4 +22,5 @@ export const DEFAULT_FEATURE_FLAGS: FeatureFlags = {
   edge_functions_system_logger: false,
   netlify_build_reduced_output: false,
   netlify_build_updated_plugin_compatibility: false,
+  netlify_build_plugin_system_log: false,
 }

packages/build/src/plugins/load.js

@@ -1,9 +1,13 @@
+import { promisify } from 'util'
+
 import { addErrorInfo } from '../error/info.js'
 import { addPluginLoadErrorStatus } from '../status/load_error.js'
 import { measureDuration } from '../time/main.js'
 
 import { callChild } from './ipc.js'
 
+const pSetTimeout = promisify(setTimeout)
+
 // Retrieve all plugins steps
 // Can use either a module name or a file path to the plugin.
 export const loadPlugins = async function ({
@@ -15,10 +19,23 @@ export const loadPlugins = async function ({
   debug,
   verbose,
   netlifyConfig,
+  featureFlags,
+  systemLog,
 }) {
   return pluginsOptions.length === 0
     ? { pluginsSteps: [], timers }
-    : await loadAllPlugins({ pluginsOptions, childProcesses, packageJson, timers, logs, debug, verbose, netlifyConfig })
+    : await loadAllPlugins({
+        pluginsOptions,
+        childProcesses,
+        packageJson,
+        timers,
+        logs,
+        debug,
+        verbose,
+        netlifyConfig,
+        featureFlags,
+        systemLog,
+      })
 }
 
 const tLoadAllPlugins = async function ({
@@ -29,10 +46,22 @@ const tLoadAllPlugins = async function ({
   debug,
   verbose,
   netlifyConfig,
+  featureFlags,
+  systemLog,
 }) {
   const pluginsSteps = await Promise.all(
     pluginsOptions.map((pluginOptions, index) =>
-      loadPlugin(pluginOptions, { childProcesses, index, packageJson, logs, debug, verbose, netlifyConfig }),
+      loadPlugin(pluginOptions, {
+        childProcesses,
+        index,
+        packageJson,
+        logs,
+        debug,
+        verbose,
+        netlifyConfig,
+        featureFlags,
+        systemLog,
+      }),
     ),
   )
   const pluginsStepsA = pluginsSteps.flat()
@@ -46,11 +75,21 @@ const loadAllPlugins = measureDuration(tLoadAllPlugins, 'load_plugins')
 // Do it by executing the plugin `load` event handler.
 const loadPlugin = async function (
   { packageName, pluginPackageJson, pluginPackageJson: { version } = {}, pluginPath, inputs, loadedFrom, origin },
-  { childProcesses, index, packageJson, logs, debug, verbose, netlifyConfig },
+  { childProcesses, index, packageJson, logs, debug, verbose, netlifyConfig, featureFlags, systemLog },
 ) {
   const { childProcess } = childProcesses[index]
   const loadEvent = 'load'
 
+  // A buffer for any data piped into the child process' stderr. We'll pipe
+  // this to system logs if we fail to load the plugin.
+  const bufferedStdErr = []
+
+  if (featureFlags.netlify_build_plugin_system_log && childProcess.stderr) {
+    childProcess.stderr.on('data', (data) => {
+      bufferedStdErr.push(data.toString().trimEnd())
+    })
+  }
+
   try {
     const { events } = await callChild({
       childProcess,
@@ -69,6 +108,15 @@ const loadPlugin = async function (
     }))
     return pluginSteps
   } catch (error) {
+    if (featureFlags.netlify_build_plugin_system_log) {
+      // Wait for stderr to be flushed.
+      await pSetTimeout(0)
+
+      bufferedStdErr.forEach((line) => {
+        systemLog(line)
+      })
+    }
+
     addErrorInfo(error, {
       plugin: { packageName, pluginPackageJson },
       location: { event: loadEvent, packageName, loadedFrom, origin },

packages/build/tests/plugins/fixtures/syntax_error/manifest.yml

@@ -0,0 +1,2 @@
+name: test
+inputs: []

packages/build/tests/plugins/fixtures/syntax_error/netlify.toml

@@ -0,0 +1,2 @@
+[[plugins]]
+package = "./plugin"

packages/build/tests/plugins/fixtures/syntax_error/plugin.js

@@ -0,0 +1,2 @@
+console.error("An error message thrown by Node.js")
+process.exit(1)

packages/build/tests/plugins/snapshots/tests.js.md

@@ -2747,3 +2747,58 @@ Generated by [AVA](https://avajs.dev).
     ────────────────────────────────────────────────────────────────␊
     ␊
     (Netlify Build completed in 1ms)`
+
+## Plugin errors that occur during the loading phase are piped to system logs
+
+> Snapshot 1
+
+    `␊
+    Netlify Build                                                 ␊
+    ────────────────────────────────────────────────────────────────␊
+    ␊
+    > Version␊
+      @netlify/build 1.0.0␊
+    ␊
+    > Flags␊
+      debug: false␊
+    ␊
+    > Current directory␊
+      packages/build/tests/plugins/fixtures/syntax_error␊
+    ␊
+    > Config file␊
+      packages/build/tests/plugins/fixtures/syntax_error/netlify.toml␊
+    ␊
+    > Context␊
+      production␊
+    ␊
+    > Loading plugins␊
+       - ./plugin@1.0.0 from netlify.toml␊
+    ␊
+    Plugin "./plugin" internal error                              ␊
+    ────────────────────────────────────────────────────────────────␊
+    ␊
+      Error message␊
+      Plugin exited with exit code 1 and signal null.␊
+      The plugin might have exited due to a bug terminating the process, such as an infinite loop.␊
+      The plugin might also have explicitly terminated the process, for example with process.exit().␊
+      Plugin methods should instead:␊
+        - on success: return␊
+        - on failure: call utils.build.failPlugin() or utils.build.failBuild()␊
+    ␊
+      Plugin details␊
+      Package:        ./plugin␊
+      Version:        1.0.0␊
+      Repository:     git+https://github.com/netlify/build.git␊
+      Report issues:  https://github.com/netlify/build/issues␊
+    ␊
+      Error location␊
+      While loading "./plugin" from netlify.toml␊
+    ␊
+      Resolved config␊
+      build:␊
+        publish: packages/build/tests/plugins/fixtures/syntax_error␊
+        publishOrigin: default␊
+      plugins:␊
+        - inputs: {}␊
+          origin: config␊
+          package: ./plugin`

packages/build/tests/plugins/tests.js

@@ -347,3 +347,22 @@ test('Plugin events that do not emit to stderr/stdout are hidden from the logs',
     .runWithBuild()
   t.snapshot(normalizeOutput(output))
 })
+
+test('Plugin errors that occur during the loading phase are piped to system logs', async (t) => {
+  const systemLogFile = await tmp.file()
+  const output = await new Fixture('./fixtures/syntax_error')
+    .withFlags({
+      debug: false,
+      featureFlags: { netlify_build_reduced_output: true, netlify_build_plugin_system_log: true },
+      systemLogFile: systemLogFile.fd,
+    })
+    .runWithBuild()
+
+  if (platform !== 'win32') {
+    const systemLog = await fs.readFile(systemLogFile.path, { encoding: 'utf8' })
+
+    t.is(systemLog.trim(), 'An error message thrown by Node.js')
+  }
+
+  t.snapshot(normalizeOutput(output))
+})