feat: Add option "diff" to print the difference instead of the output

README.md

@@ -122,6 +122,7 @@ Usage: `jsonlint [options] [<file, directory, pattern> ...]`
     -E, --extensions [ext]       file extensions to process for directory walk
                                   (default: ["json","JSON"])
     -i, --in-place               overwrite the input files
+    -j, --diff                   print difference instead of writing the output
     -k, --check                  check that the input is equal to the output
     -t, --indent [num|char]      number of spaces or specific characters
                                   to use for indentation (default: 2)
@@ -187,6 +188,8 @@ The configuration is an object with the following properties, described above, w
 | sort-keys | sortKeys |
 | extensions | |
 | in-place | inPlace |
+| diff | |
+| check | |
 | indent | |
 | compact | |
 | mode | |

lib/cli.js

@@ -21,6 +21,7 @@ const commander = require('commander')
   .option('-s, --sort-keys', 'sort object keys (not when prettifying)')
   .option('-E, --extensions [ext]', 'file extensions to process for directory walk', collectValues, ['json', 'JSON'])
   .option('-i, --in-place', 'overwrite the input files')
+  .option('-j, --diff', 'print difference instead of writing the output')
   .option('-k, --check', 'check that the input is equal to the output')
   .option('-t, --indent [num|char]', 'number of spaces or specific characters to use for indentation', 2)
   .option('-c, --compact', 'compact error display')
@@ -87,6 +88,7 @@ if (params.config === false) {
 }
 
 const extensions = options.extensions.map(extension => '.' + extension)
+let reported
 
 function convertConfig (config) {
   const result = {}
@@ -108,10 +110,16 @@ function mergeOptions (target, ...sources) {
   return target
 }
 
-function logNormalError (error, file) {
-  if (process.exitCode > 0) {
+function separateBlocks() {
+  if (reported) {
     console.log()
+  } else {
+    reported = true
   }
+}
+
+function logNormalError (error, file) {
+  separateBlocks()
   console.log('File:', file)
   console.error(error.message)
 }
@@ -227,6 +235,33 @@ function checkContents (file, source, parsed) {
   }
 }
 
+function diffContents(file, source, parsed) {
+  const { createTwoFilesPatch, structuredPatch } = require('diff')
+  const compact = options.quiet || options.compact
+  let diff, length
+  if (compact) {
+    diff = structuredPatch(`${file}.orig`, file, source, parsed, '', '', { context: 3 })
+    length = diff.hunks && diff.hunks.length
+  } else {
+    diff = createTwoFilesPatch(`${file}.orig`, file, source, parsed, '', '', { context: 3 })
+    length = diff.split(/\r?\n/).length - 4
+  }
+  if (length > 0) {
+    if (compact) {
+      const hunk = length === 1 ? 'hunk' : 'hunks'
+      console.info(`${file}: ${length} ${hunk}`)
+    } else {
+      separateBlocks()
+      console.log('File:', file)
+      console.log(diff)
+    }
+  } else {
+    if (compact) {
+      console.info(`${file}: no difference`)
+    }
+  }
+}
+
 function processFile (file) {
   file = normalize(file)
   if (options.logFiles) {
@@ -238,6 +273,8 @@ function processFile (file) {
     writeFileSync(file, ensureLineBreak(parsed, source))
   } else if (options.check) {
     checkContents(file, source, ensureLineBreak(parsed, source))
+  } else if (options.diff) {
+    diffContents(file, source, ensureLineBreak(parsed, source))
   } else {
     if (!(options.quiet || options.logFiles)) {
       console.log(parsed)
@@ -311,6 +348,8 @@ function main () {
       const parsed = processContents(source, file)
       if (options.check) {
         checkContents(file, source, ensureLineBreak(parsed, source))
+      } else if (options.diff) {
+        diffContents(file, source, ensureLineBreak(parsed, source))
       } else if (!(options.quiet || options.logFiles)) {
         console.log(parsed)
       }