perf(reporter): print a warning summary

Sometimes, when installing new dependencies that rely on many peer dependencies,
or when running installation on a huge monorepo, there will be hundreds or thousands of warnings.
Printing many messages to the terminal is expensive and reduces speed,
so pnpm will only print a few warnings and report the total number of the unprinted warnings.

PR #2826

.changeset/tidy-dingos-happen.md

@@ -0,0 +1,5 @@
+---
+"@pnpm/default-reporter": minor
+---
+
+Sometimes, when installing new dependencies that rely on many peer dependencies, or when running installation on a huge monorepo, there will be hundreds or thousands of warnings. Printing many messages to the terminal is expensive and reduces speed, so pnpm will only print a few warnings and report the total number of the unprinted warnings.

packages/default-reporter/src/reporterForClient/reportMisc.ts

@@ -1,6 +1,7 @@
 import { Config } from '@pnpm/config'
 import { Log, RegistryLog } from '@pnpm/core-loggers'
 import { LogLevel } from '@pnpm/logger'
+import PushStream from '@zkochan/zen-push'
 import reportError from '../reportError'
 import formatWarn from './utils/formatWarn'
 import { autozoom } from './utils/zooming'
@@ -16,6 +17,8 @@ const LOG_LEVEL_NUMBER: Record<LogLevel, number> = {
 }
 // eslint-enable:object-literal-sort-keys
 
+const MAX_SHOWN_WARNINGS = 5
+
 export default (
   log$: {
     registry: most.Stream<RegistryLog>
@@ -29,22 +32,54 @@ export default (
   }
 ) => {
   const maxLogLevel = LOG_LEVEL_NUMBER[opts.logLevel ?? 'info'] ?? LOG_LEVEL_NUMBER['info']
+  const reportWarning = makeWarningReporter(opts)
   return most.merge(log$.registry, log$.other)
     .filter((obj) => LOG_LEVEL_NUMBER[obj.level] <= maxLogLevel &&
       (obj.level !== 'info' || !obj['prefix'] || obj['prefix'] === opts.cwd))
     .map((obj) => {
       switch (obj.level) {
-      case 'warn':
-        return autozoom(opts.cwd, obj.prefix, formatWarn(obj.message), opts)
+      case 'warn': {
+        return reportWarning(obj)
+      }
       case 'error':
         if (obj['message']?.['prefix'] && obj['message']['prefix'] !== opts.cwd) {
-          return `${obj['message']['prefix'] as string}:` + os.EOL + reportError(obj, opts.config)
+          return most.of({
+            msg: `${obj['message']['prefix'] as string}:` + os.EOL + reportError(obj, opts.config),
+          })
         }
-        return reportError(obj, opts.config)
+        return most.of({ msg: reportError(obj, opts.config) })
       default:
-        return obj['message']
+        return most.of({ msg: obj['message'] })
       }
     })
-    .map((msg) => ({ msg }))
-    .map(most.of)
+}
+
+// Sometimes, when installing new dependencies that rely on many peer dependencies,
+// or when running installation on a huge monorepo, there will be hundreds or thousands of warnings.
+// Printing many messages to the terminal is expensive and reduces speed,
+// so pnpm will only print a few warnings and report the total number of the unprinted warnings.
+function makeWarningReporter (
+  opts: {
+    cwd: string
+    zoomOutCurrent: boolean
+  }
+) {
+  let warningsCounter = 0
+  let collapsedWarnings: PushStream<{ msg: string }>
+  return (obj: { prefix: string, message: string }) => {
+    warningsCounter++
+    if (warningsCounter <= MAX_SHOWN_WARNINGS) {
+      return most.of({ msg: autozoom(opts.cwd, obj.prefix, formatWarn(obj.message), opts) })
+    }
+    const warningMsg = formatWarn(`${warningsCounter - MAX_SHOWN_WARNINGS} other warnings`)
+    if (!collapsedWarnings) {
+      collapsedWarnings = new PushStream()
+      // For some reason, without using setTimeout, the warning summary is printed above the rest of the warnings
+      // Even though the summary event happens last. Probably a bug in "most".
+      setTimeout(() => collapsedWarnings.next({ msg: warningMsg }), 0)
+      return most.from(collapsedWarnings.observable)
+    }
+    setTimeout(() => collapsedWarnings!.next({ msg: warningMsg }), 0)
+    return most.never()
+  }
 }

packages/default-reporter/test/index.ts

@@ -1029,3 +1029,40 @@ test('logLevel=error', t => {
     },
   })
 })
+
+test('warnings are collapsed', t => {
+  const prefix = process.cwd()
+  const output$ = toOutput$({
+    context: {
+      argv: ['install'],
+      config: { dir: prefix } as Config,
+    },
+    reportingOptions: {
+      logLevel: 'warn',
+    },
+    streamParser: createStreamParser(),
+  })
+
+  logger.warn({ message: 'Some issue 1', prefix })
+  logger.warn({ message: 'Some issue 2', prefix })
+  logger.warn({ message: 'Some issue 3', prefix })
+  logger.warn({ message: 'Some issue 4', prefix })
+  logger.warn({ message: 'Some issue 5', prefix })
+  logger.warn({ message: 'Some issue 6', prefix })
+  logger.warn({ message: 'Some issue 7', prefix })
+
+  t.plan(1)
+
+  output$.skip(6).take(1).subscribe({
+    complete: () => t.end(),
+    error: t.end,
+    next: output => {
+      t.equal(output, `${WARN} Some issue 1
+${WARN} Some issue 2
+${WARN} Some issue 3
+${WARN} Some issue 4
+${WARN} Some issue 5
+${WARN} 2 other warnings`)
+    },
+  })
+})