fix: Set up listeners first, in case of long write to stdin. (#520)

Co-authored-by: Jordan Rickman <jordan@alloy.com>
Co-authored-by: Jordan Rickman <jordan.rickman.42@gmail.com>

Author: Jordan-Alloy

src/exec.js

@@ -12,7 +12,26 @@ const exec = (command, args, stdin, cwd) => {
 
     const process = childProcess.spawn(command, args, spawnOptions)
 
+    // All of these handlers can close the Promise, so guard against rejecting it twice.
+    let promiseAlreadyRejected = false
+    process.on('close', code => {
+      if (!promiseAlreadyRejected) {
+        promiseAlreadyRejected = true
+        if (code !== 0) {
+          return reject(Error(stderr))
+        } else {
+          return resolve(stripFinalNewline(stdout))
+        }
+      }
+    })
+
     if (stdin) {
+      process.stdin.on('error', err => {
+        if (!promiseAlreadyRejected) {
+          promiseAlreadyRejected = true
+          return reject(err)
+        }
+      })
       process.stdin.setEncoding('utf-8')
       process.stdin.write(stdin)
       process.stdin.end()
@@ -26,14 +45,6 @@ const exec = (command, args, stdin, cwd) => {
     process.stderr.on('data', data => {
       stderr += data
     })
-
-    process.on('close', code => {
-      if (code !== 0) {
-        return reject(Error(stderr))
-      } else {
-        return resolve(stripFinalNewline(stdout))
-      }
-    })
   })
 }
 

src/jq.test.js

@@ -1,5 +1,6 @@
 import { expect } from 'chai'
 import path from 'path'
+import { readFileSync } from 'fs'
 
 import { run } from './jq'
 import { FILTER_UNDEFINED_ERROR } from './command'
@@ -74,6 +75,31 @@ describe('jq core', () => {
       })
   })
 
+  it('should catch errors from child process stdin', done => {
+    // This is a very specific case of error, only triggered if:
+    // 1) The jq process exits early (e.g. due to an invalid filter)
+    // AND
+    // 2) We are trying to send a large amount of data over stdin,
+    //    (which will take longer to do than jq takes to exit).
+    const largeJsonString = JSON.parse(readFileSync(PATH_LARGE_JSON_FIXTURE))
+    run(FILTER_INVALID, largeJsonString, { input: 'json' })
+      .then(result => {
+        done('Expected an error to be thrown from child process stdin')
+      })
+      .catch(error => {
+        expect(error).to.be.an.instanceof(Error)
+        // On Mac/Linux, the error code is "EPIPE".
+        // On Windows, the equivalent code is "EOF".
+        expect(error.message).to.be.oneOf(['write EPIPE', 'write EOF'])
+        expect(error.code).to.be.oneOf(['EPIPE', 'EOF'])
+        expect(error.syscall).to.equal('write')
+        done()
+      })
+      .catch(error => {
+        done(error)
+      })
+  })
+
   it('should fail on an undefined filter', done => {
     run(undefined, PATH_JSON_FIXTURE)
       .catch(error => {