feat: output json formatted errors on stdout

This also adds a new output method `outputBuffer()` which will buffer all output until it is flushed in the exit handler. This allows the exit handler to catch any errors and append them to the output when in json mode. This was necessary to not introduce a regression in the case of #2150. BREAKING CHANGE: `npm` now outputs some json errors on stdout. Previously `npm` would output all json formatted errors on stderr, making it difficult to parse as the stderr stream usually has logs already written to it. In the future, `npm` will differentiate between errors and crashes. Errors, such as `E404` and `ERESOLVE`, will be handled and will continue to be output on stdout. In the case of a crash, `npm` will log the error as usual but will not attempt to display it as json, even in `--json` mode. Moving a case from the category of an error to a crash will not be considered a breaking change. For more information see npm/rfcs#482. Closes #2740 Closes npm/statusboard#589

Author: lukekarrys

lib/commands/ls.js

@@ -177,7 +177,7 @@ class LS extends ArboristWorkspaceCmd {
  const [rootError] = tree.errors.filter(e =>
  e.code === 'EJSONPARSE' && e.path === resolve(path, 'package.json'))
 
- this.npm.output(
+ this.npm.outputBuffer(
  json
  ? jsonOutput({ path, problems, result, rootError, seenItems })
  : parseable

lib/npm.js

@@ -40,6 +40,7 @@ class Npm extends EventEmitter {
  #argvClean = []
  #chalk = null
 
+ #outputBuffer = []
  #logFile = new LogFile()
  #display = new Display()
  #timers = new Timers({
@@ -466,6 +467,37 @@ class Npm extends EventEmitter {
  log.showProgress()
  }
 
+ outputBuffer (item) {
+ this.#outputBuffer.push(item)
+ }
+
+ flushOutput (jsonError) {
+ if (!jsonError && !this.#outputBuffer.length) {
+ return
+ }
+
+ if (this.config.get('json')) {
+ const jsonOutput = this.#outputBuffer.reduce((acc, item) => {
+ if (typeof item === 'string') {
+ // try to parse it as json in case its a string
+ try {
+ item = JSON.parse(item)
+ } catch {
+ return acc
+ }
+ }
+ return { ...acc, ...item }
+ }, {})
+ this.output(JSON.stringify({ ...jsonOutput, ...jsonError }, null, 2))
+ } else {
+ for (const item of this.#outputBuffer) {
+ this.output(item)
+ }
+ }
+
+ this.#outputBuffer.length = 0
+ }
+
  outputError (...msg) {
  log.clearProgress()
  // eslint-disable-next-line no-console

lib/utils/exit-handler.js

@@ -136,6 +136,7 @@ const exitHandler = err => {
 
  let exitCode
  let noLogMessage
+ let jsonError
 
  if (err) {
  exitCode = 1
@@ -198,14 +199,13 @@ const exitHandler = err => {
  }
 
  if (hasLoadedNpm && npm.config.get('json')) {
- const error = {
+ jsonError = {
  error: {
  code: err.code,
  summary: messageText(summary),
  detail: messageText(detail),
  },
  }
- npm.outputError(JSON.stringify(error, null, 2))
  }
 
  if (typeof err.errno === 'number') {
@@ -216,6 +216,10 @@ const exitHandler = err => {
  }
  }
 
+ if (hasLoadedNpm) {
+ npm.flushOutput(jsonError)
+ }
+
  log.verbose('exit', exitCode || 0)
 
  showLogFileError = (hasLoadedNpm && npm.silent) || noLogMessage

test/fixtures/mock-npm.js

@@ -238,6 +238,15 @@ class MockNpm {
  }
  this._mockOutputs.push(msg)
  }
+
+ // with the older fake mock npm there is no
+ // difference between output and outputBuffer
+ // since it just collects the output and never
+ // calls the exit handler, so we just mock the
+ // method the same as output.
+ outputBuffer (...msg) {
+ this.output(...msg)
+ }
 }
 
 const FakeMockNpm = (base = {}, t) => {

test/lib/utils/exit-handler.js

@@ -208,15 +208,15 @@ t.test('exit handler called - no npm with error without stack', async (t) => {
 })
 
 t.test('console.log output using --json', async (t) => {
- const { exitHandler, outputErrors } = await mockExitHandler(t, {
+ const { exitHandler, outputs } = await mockExitHandler(t, {
  config: { json: true },
  })
 
  await exitHandler(err('Error: EBADTHING Something happened'))
 
  t.equal(process.exitCode, 1)
  t.same(
- JSON.parse(outputErrors[0]),
+ JSON.parse(outputs[0]),
  {
  error: {
  code: 'EBADTHING', // should default error code to E[A-Z]+
@@ -228,6 +228,50 @@ t.test('console.log output using --json', async (t) => {
  )
 })
 
+t.test('merges output buffers errors with --json', async (t) => {
+ const { exitHandler, outputs, npm } = await mockExitHandler(t, {
+ config: { json: true },
+ })
+
+ npm.outputBuffer({ output_data: 1 })
+ npm.outputBuffer(JSON.stringify({ more_data: 2 }))
+ npm.outputBuffer('not json, will be ignored')
+
+ await exitHandler(err('Error: EBADTHING Something happened'))
+
+ t.equal(process.exitCode, 1)
+ t.same(
+ JSON.parse(outputs[0]),
+ {
+ output_data: 1,
+ more_data: 2,
+ error: {
+ code: 'EBADTHING', // should default error code to E[A-Z]+
+ summary: 'Error: EBADTHING Something happened',
+ detail: 'Error: EBADTHING Something happened',
+ },
+ },
+ 'should output expected json output'
+ )
+})
+
+t.test('output buffer without json', async (t) => {
+ const { exitHandler, outputs, npm, logs } = await mockExitHandler(t)
+
+ npm.outputBuffer('output_data')
+ npm.outputBuffer('more_data')
+
+ await exitHandler(err('Error: EBADTHING Something happened'))
+
+ t.equal(process.exitCode, 1)
+ t.same(
+ outputs,
+ [['output_data'], ['more_data']],
+ 'should output expected output'
+ )
+ t.match(logs.error, [['code', 'EBADTHING']])
+})
+
 t.test('throw a non-error obj', async (t) => {
  const { exitHandler, logs } = await mockExitHandler(t)