added color support

lib/diff.js

@@ -1,5 +1,7 @@
 const fs = require('fs')
+const { EOL } = require('os')
 const { promisify } = require('util')
+const ansi = require('ansi-styles')
 const Arborist = require('@npmcli/arborist')
 const jsDiff = require('diff')
 const pacote = require('pacote')
@@ -50,6 +52,8 @@ const getMime = () => {
     'patents',
     'readme',
     'ts',
+    'yml',
+    'yaml',
     'flow'
   ], 'text/plain')
 
@@ -112,7 +116,34 @@ const untar = ({ files, item, prefix, opts, refs }) =>
       .end(item)
   })
 
-const printDiff = ({ files, refs, versions }) => {
+const colorizeDiff = ({ res, headerLength }) => {
+  const colors = {
+    charsRemoved: ansi.bgRed,
+    charsAdded: ansi.bgGreen,
+    removed: ansi.red,
+    added: ansi.green,
+    header: ansi.yellow,
+    section: ansi.magenta
+  }
+  const colorize = (str, colorId) => {
+    var { open, close } = colors[colorId]
+    // avoid highlighting the "\n" (would highlight till the end of the line)
+    return str.replace(/[^\n\r]+/g, open + '$&' + close)
+  }
+
+  // this RegExp will include all the `\n` chars into the lines, easier to join
+  const lines = res.split(/^/m)
+
+  const start = colorize(lines.slice(0, headerLength || 2).join(''), 'header')
+  const end = lines.slice(headerLength || 2).join('')
+    .replace(/^-.*/gm, colorize('$&', 'removed'))
+    .replace(/^\+.*/gm, colorize('$&', 'added'))
+    .replace(/^@@.+@@/gm, colorize('$&', 'section'))
+
+  return start + end
+}
+
+const printDiff = ({ files, opts, refs, versions }) => {
   for (const filename of files.values()) {
     const names = {
       a: `a/${filename}`,
@@ -135,9 +166,31 @@ const printDiff = ({ files, refs, versions }) => {
 
     if (contents.a === contents.b) continue
 
-    let res
+    let res = ''
+    let headerLength = 0
+    const header = str => {
+      headerLength++
+      res += `${str}${EOL}`
+    }
+
+    // manually build a git diff-compatible header
+    header(`diff --git ${names.a} ${names.b}`)
+    if (modes.a === modes.b) {
+      fileMode = filenames.a.mode
+    } else {
+      if (modes.a && modes.b) {
+        header(`old mode ${modes.a}`)
+        header(`new mode ${modes.b}`)
+      } else if (modes.a && !modes.b) {
+        header(`deleted file mode ${modes.a}`)
+      } else if (!modes.a && modes.b) {
+        header(`new file mode ${modes.b}`)
+      }
+    }
+    header(`index ${versions.a}..${versions.b} ${fileMode}`)
+
     if (diffFileType(filename)) {
-      res = jsDiff.createTwoFilesPatch(
+      res += jsDiff.createTwoFilesPatch(
         names.a,
         names.b,
         contents.a || '',
@@ -149,27 +202,17 @@ const printDiff = ({ files, refs, versions }) => {
         '===================================================================\n',
         ''
       )
+      headerLength += 2
     } else {
-      res = `--- ${names.a}\n+++ ${names.b}`
+      header(`--- ${names.a}`)
+      header(`+++ ${names.b}`)
     }
 
-    output(`diff --git ${names.a} ${names.b}`)
-
-    if (modes.a === modes.b) {
-      fileMode = filenames.a.mode
-    } else {
-      if (modes.a && modes.b) {
-        output(`old mode ${modes.a}`)
-        output(`new mode ${modes.b}`)
-      } else if (modes.a && !modes.b) {
-        output(`deleted file mode ${modes.a}`)
-      } else if (!modes.a && modes.b) {
-        output(`new file mode ${modes.b}`)
-      }
-    }
-
-    output(`index ${versions.a}..${versions.b} ${fileMode}`)
-    output(res)
+    output(
+      opts.color
+        ? colorizeDiff({ res, headerLength })
+        : res
+    )
   }
 }
 
@@ -224,6 +267,7 @@ const diffSelf = async () => {
 
   printDiff({
     files,
+    opts,
     refs,
     versions
   })
@@ -293,6 +337,7 @@ const diffComparison = async (specs) => {
 
   printDiff({
     files,
+    opts,
     refs,
     versions
   })