GitHub Issue #86 - support passing code directly via stdin

README.md

@@ -91,6 +91,9 @@ standard-clj fix
 
 ## or pass a config file explicitly using the --config argument
 standard-clj list --config /home/user1/my-project/my-standard-cfg.json
+
+## pipe code directly to the fix command using "-"
+echo '(ns my.company.core (:require [clojure.string :as str]))' | standard-clj fix -
 ```
 
 #### `list` command
@@ -137,6 +140,17 @@ Returns exit code 0 if all files have been formatted, 1 otherwise.
 standard-clj fix src/ test/ deps.edn
 ```
 
+#### `fix -` command (stdin / stdout)
+
+Use `standard-clj fix -` to pipe code directly via stdin.
+
+Prints the formatted code to stdout with error code 0 if successful. Prints an
+error message to stderr with error code 1 otherwise.
+
+```sh
+echo '(ns my.company.core (:require [clojure.string :as str]))' | standard-clj fix -
+```
+
 #### Which files will be formatted?
 
 `standard-clj` accepts several ways to know which files to format:

cli.mjs

@@ -377,7 +377,8 @@ function processCheckCmd (argv) {
   }
 }
 
-function processFixCmd (argv) {
+// this is the fix command when not reading input from stdin
+function processFixCmdNotStdin (argv) {
   setLogLevel(argv['log-level'])
 
   printProgramInfo({ command: 'fix' })
@@ -420,6 +421,38 @@ function processFixCmd (argv) {
   }
 }
 
+// fix command when reading input from stdin
+async function processFixCmdStdin (argv) {
+  const stdinStr = await readStream(process.stdin)
+
+  if (!isString(stdinStr) || stdinStr === '') {
+    exitSad('Nothing found on stdin. Please pipe some Clojure code to stdin when using "standard-clj fix -"')
+  } else {
+    let formatResult = null
+    try {
+      formatResult = standardClj.format(stdinStr)
+    } catch (e) {}
+
+    if (formatResult && formatResult.status === 'success') {
+      console.log(formatResult.out)
+      exitHappy()
+    } else if (formatResult && formatResult.status === 'error' && isString(formatResult.reason)) {
+      exitSad('Failed to format code: ' + formatResult.reason)
+    } else {
+      exitSad('Failed to format your code due to unknown error with the format() function. Please help the standard-clj project by opening an issue to report this 🙏')
+    }
+  }
+}
+
+function processFixCmd (argv) {
+  const lastArg = getLastItemInArray(argv._)
+  if (lastArg === '-') {
+    processFixCmdStdin(argv)
+  } else {
+    processFixCmdNotStdin(argv)
+  }
+}
+
 function processListCmd (argv) {
   const filesSet = getFilesFromArgv(argv, 'list')
   const sortedFiles = setToArray(filesSet).sort()
@@ -501,6 +534,16 @@ function setToArray (s) {
   return Array.from(s)
 }
 
+// returns the last item in an Array, or null if the Array is empty
+function getLastItemInArray (a) {
+  const size = a.length
+  if (size === 0) {
+    return null
+  } else {
+    return a[size - 1]
+  }
+}
+
 // some older versions of node.js do not have Set.difference
 function setDifference (setA, setB) {
   if (typeof Set.prototype.difference === 'function') {
@@ -548,3 +591,10 @@ function fileStr (numFiles) {
   if (numFiles === 1) return 'file'
   else return 'files'
 }
+
+// https://stackoverflow.com/a/54565854
+async function readStream (stream) {
+  const chunks = []
+  for await (const chunk of stream) { chunks.push(chunk) }
+  return Buffer.concat(chunks).toString('utf8')
+}