feat: Introduce a check that the formatted output is the same as the input

Checks if all JSON files coply with the coding standard,
not only being valid JSON.

Author: prantlf

.vscode/launch.json

@@ -2,23 +2,22 @@
   "version": "0.2.0",
   "configurations": [
     {
+      "name": "cli",
       "type": "node",
       "request": "launch",
-      "name": "cli",
       "program": "${workspaceRoot}/lib/cli.js",
       "args": [
-        "-M",
-        "json5",
-        "test/passes/json5.txt"
+        "-k",
+        "package.json"
       ],
       "skipFiles": [
         "<node_internals>/**/*.js"
       ]
     },
     {
+      "name": "test",
       "type": "node",
       "request": "launch",
-      "name": "test",
       "program": "${workspaceRoot}/test/parse2.js",
       "args": [
         "--native-parser"
@@ -28,9 +27,9 @@
       ]
     },
     {
+      "name": "fail",
       "type": "node",
       "request": "launch",
-      "name": "fail",
       "program": "${workspaceRoot}/benchmarks/fail",
       "skipFiles": [
         "<node_internals>/**/*.js"

README.md

@@ -14,6 +14,7 @@ This is a fork of the original project ([zaach/jsonlint](https://github.com/zaac
 * Provides 100% compatible interface to the native `JSON.parse` method.
 * Optionally recognizes JavaScript-style comments (CJSON) and single quoted strings (JSON5).
 * Optionally ignores trailing commas and reports duplicate object keys as an error.
+* Optionally checks that also the expected format matches, including sorted object keys.
 * Supports [JSON Schema] drafts 04, 06 and 07.
 * Offers pretty-printing including comment-stripping and object keys without quotes (JSON5).
 * Prefers the native JSON parser if possible to run [7x faster than the custom parser].
@@ -92,6 +93,23 @@ The same parameters can be passed from a configuration file:
 }
 ```
 
+The input can be checked not only to be a valid JSON, but also to be formatted according to the coding standard. For example, check that there is a trailing li break in each JSON file, in addition to alphabetically sorted keys and no duplicate keys:
+
+    $ jsonlint -ksDr *.json
+
+    File: package.json
+    Formatted output differs
+    ===================================================================
+    --- package.json.orig
+    +++ package.json
+    @@ -105,4 +105,4 @@
+        "lint",
+        "jsonlint"
+      ]
+    -}
+    +}
+    \ No newline at end of file
+
 ### Usage
 
 Usage: `jsonlint [options] [<file, directory, pattern> ...]`
@@ -104,6 +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
+    -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)
     -c, --compact                compact error display

lib/cli.js

@@ -3,7 +3,6 @@
 const { readdirSync, readFileSync, statSync, writeFileSync } = require('fs')
 const { extname, join, normalize } = require('path')
 const { isDynamicPattern, sync } = require('fast-glob')
-const { cosmiconfigSync } = require('cosmiconfig')
 const { parse, tokenize } = require('./jsonlint')
 const { format } = require('./formatter')
 const { print } = require('./printer')
@@ -22,6 +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('-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')
   .option('-M, --mode [mode]', 'set other parsing flags according to a format type', 'json')
@@ -79,6 +79,7 @@ let options
 if (params.config === false) {
   options = params
 } else {
+  const { cosmiconfigSync } = require('cosmiconfig')
   const configurator = cosmiconfigSync('jsonlint')
   const { config = {} } = (params.config && configurator.load(params.config)) ||
     configurator.search() || {}
@@ -197,24 +198,49 @@ function processContents (source, file) {
   }
 }
 
+function ensureLineBreak (parsed, source) {
+  const lines = source.split(/\r?\n/)
+  const newLine = !lines[lines.length - 1]
+  if (options.trailingNewline === true ||
+      (options.trailingNewline !== false && newLine)) {
+    parsed += '\n'
+  }
+  return parsed
+}
+
+function checkContents (file, source, parsed) {
+  const { createTwoFilesPatch } = require('diff')
+  const diff = createTwoFilesPatch(`${file}.orig`, file, source, parsed, '', '', { context: 3 })
+  if (diff.split(/\r?\n/).length > 4) {
+    const err = new Error('Formatted output differs')
+    if (options.compact) {
+      logCompactError(err, file)
+    } else {
+      logNormalError(err, file)
+    }
+    console.log(diff)
+    if (options.continue) {
+      process.exitCode = 1
+    } else {
+      process.exit(1)
+    }
+  }
+}
+
 function processFile (file) {
   file = normalize(file)
   if (options.logFiles) {
     console.log(file)
   }
-  const original = readFileSync(file, 'utf8')
-  let source = processContents(original, file)
+  const source = readFileSync(file, 'utf8')
+  const parsed = processContents(source, file)
   if (options.inPlace) {
-    const lines = original.split(/\r?\n/)
-    const newLine = !lines[lines.length - 1]
-    if (options.trailingNewline === true ||
-        (options.trailingNewline !== false && newLine)) {
-      source += '\n'
-    }
-    writeFileSync(file, source)
+    writeFileSync(file, ensureLineBreak(parsed, source))
+  } else if (options.check) {
+    checkContents(file, source, ensureLineBreak(parsed, source))
   } else {
     if (!(options.quiet || options.logFiles)) {
-      console.log(source)
+      console.log(parsed)
     }
   }
 }
@@ -278,11 +304,14 @@ function main () {
       source += chunk.toString('utf8')
     })
     stdin.on('end', () => {
+      const file = '<stdin>'
       if (options.logFiles) {
-        console.log('<stdin>')
+        console.log(file)
       }
-      const parsed = processContents(source, '<stdin>')
-      if (!(options.quiet || options.logFiles)) {
+      const parsed = processContents(source, file)
+      if (options.check) {
+        checkContents(file, source, ensureLineBreak(parsed, source))
+      } else if (!(options.quiet || options.logFiles)) {
         console.log(parsed)
       }
     })

package.json

@@ -77,15 +77,16 @@
   "dependencies": {
     "ajv": "6.12.6",
     "commander": "9.2.0",
-    "cosmiconfig": "^7.0.1",
+    "cosmiconfig": "7.0.1",
+    "diff": "5.0.0",
     "fast-glob": "3.2.11"
   },
   "devDependencies": {
-    "@semantic-release/changelog": "^6.0.1",
-    "@semantic-release/git": "^10.0.1",
-    "@types/node": "17.0.30",
-    "@typescript-eslint/eslint-plugin": "5.21.0",
-    "@typescript-eslint/parser": "5.21.0",
+    "@semantic-release/changelog": "6.0.1",
+    "@semantic-release/git": "10.0.1",
+    "@types/node": "17.0.31",
+    "@typescript-eslint/eslint-plugin": "5.22.0",
+    "@typescript-eslint/parser": "5.22.0",
     "eslint": "8.14.0",
     "eslint-config-standard": "17.0.0",
     "eslint-plugin-import": "2.26.0",