feat: allow filtering properties, close #2

README.md

@@ -70,6 +70,25 @@ execaWrap('failing-command', ['its', 'arguments'])
   })
 ```
 
+### Filtering properties
+
+If you are not interested in every returned property, you can filter and get only some
+properties. For example, let us grab `command` and `stdout`
+
+```js
+execaWrap('ls', ['src'], {filter: ['cmd', 'stdout']})
+// command: ls src
+// stdout
+// ------
+```
+
+For a single filter, just use a string or single item array
+
+```js
+execaWrap('ls', ['src'], {filter: 'cmd'})
+// command: ls src
+```
+
 ### Small print
 
 Author: Gleb Bahmutov <gleb.bahmutov@gmail.com> © 2017

__snapshots__/execa-wrap-spec.js

@@ -1,3 +1,14 @@
+exports['fields filter 1'] = `
+  command: ls src
+  stdout:
+  -------
+  execa-wrap-spec.js
+  index.js
+  windows-spec.js
+  -------
+  
+`
+
 exports['ls src 1'] = `
 
   command: ls src
@@ -39,3 +50,13 @@ exports['boo src 1'] = `
   -------
   
 `
+
+exports['single field filter 1'] = `
+  stdout:
+  -------
+  execa-wrap-spec.js
+  index.js
+  windows-spec.js
+  -------
+  
+`

src/execa-wrap-spec.js

@@ -14,5 +14,16 @@ if (os.platform() !== 'win32') {
     it('failing', () => {
       return execaWrap('boo', ['src']).then(snapshot.bind(null, 'boo src'))
     })
+
+    it('can filter single field', () => {
+      return execaWrap('ls', ['src'], { filter: 'stdout' }).then(
+        snapshot.bind(null, 'single field filter')
+      )
+    })
+    it('can filter several fields', () => {
+      return execaWrap('ls', ['src'], { filter: ['cmd', 'stdout'] }).then(
+        snapshot.bind(null, 'fields filter')
+      )
+    })
   })
 }

src/index.js

@@ -9,10 +9,42 @@ const stripFields = R.evolve({
   stderr: stripAnsi
 })
 
-const makeText = execResult => {
-  const stdout = indentString(stripLeadingIndent(execResult.stdout), 2).trim()
-  const stderr = indentString(stripLeadingIndent(execResult.stderr), 2).trim()
+const makeFilteredText = result => {
+  // indent with 2 spaces every line
+  let message = ''
+  if (result.cmd) {
+    message += `  command: ${result.cmd}\n`
+  }
+  if (result.code) {
+    message += `  code: ${result.code}\n`
+  }
+  if (result.failed) {
+    message += `  failed: ${result.failed}\n`
+  }
+  if (result.killed) {
+    message += `  killed: ${result.killed}\n`
+  }
+  if (result.signal) {
+    message += `  signal: ${result.signal}\n`
+  }
+  if (result.stdout) {
+    message += `  stdout:
+  -------
+  ${result.stdout}
+  -------
+  `
+  }
+  if (result.stderr) {
+    message += `  stderr:
+  -------
+  ${result.stderr}
+  -------
+  `
+  }
+  return message
+}
 
+const makeAllText = execResult => {
   return `
   command: ${execResult.cmd}
   code: ${execResult.code}
@@ -23,20 +55,37 @@ const makeText = execResult => {
 
   stdout:
   -------
-  ${stdout}
+  ${execResult.stdout}
   -------
   stderr:
   -------
-  ${stderr}
+  ${execResult.stderr}
   -------
   `
 }
 
-function execWrapper (cmd, args) {
+const makeText = (options = {}) => execResult => {
+  let { filter } = options
+
+  const result = R.clone(execResult)
+  result.stdout = indentString(stripLeadingIndent(result.stdout), 2).trim()
+  result.stderr = indentString(stripLeadingIndent(result.stderr), 2).trim()
+
+  if (typeof filter === 'string') {
+    filter = [filter]
+  }
+  if (Array.isArray(filter) && filter.length) {
+    return makeFilteredText(R.pick(filter, result))
+  }
+
+  return makeAllText(result)
+}
+
+function execWrapper (cmd, args, options = {}) {
   const child = execa(cmd, args)
   child.stdout.pipe(process.stdout)
   child.stderr.pipe(process.stderr)
-  return child.then(stripFields, stripFields).then(makeText)
+  return child.then(stripFields, stripFields).then(makeText(options))
 }
 
 module.exports = execWrapper