5 files changed, 94 insertions, 5 deletions

diff --git a/lib/commands/ls.js b/lib/commands/ls.js
index 6812c3923..7eebdf691 100644
--- a/lib/commands/ls.js
+++ b/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
diff --git a/lib/npm.js b/lib/npm.js
index 763c9b7a3..9fbda9073 100644
--- a/lib/npm.js
+++ b/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
diff --git a/lib/utils/exit-handler.js b/lib/utils/exit-handler.js
index 2574a83fc..a9e061de7 100644
--- a/lib/utils/exit-handler.js
+++ b/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
diff --git a/test/fixtures/mock-npm.js b/test/fixtures/mock-npm.js
index 0318eadeb..8a744cd55 100644
--- a/test/fixtures/mock-npm.js
+++ b/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) => {
diff --git a/test/lib/utils/exit-handler.js b/test/lib/utils/exit-handler.js
index 7e3137013..d22ec4dd1 100644
--- a/test/lib/utils/exit-handler.js
+++ b/test/lib/utils/exit-handler.js
@@ -208,7 +208,7 @@ 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 },
   })
 
@@ -216,7 +216,7 @@ t.test('console.log output using --json', async (t) => {
 
   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)