feat: add npm diff

- As proposed in RFC: npm/rfcs#144

docs/content/commands/npm-diff.md

@@ -0,0 +1,159 @@
+---
+title: npm-diff
+section: 1
+description: The registry diff command
+---
+
+### Synopsis
+
+```bash
+npm diff
+npm diff <pkg-name>
+npm diff <version-a> [<version-b>]
+npm diff <spec-a> [<spec-b>]
+```
+
+### Description
+
+Similar to its `git diff` counterpart, this command will print diff patches
+of files for packages published to the npm registry.
+
+A variation of different arguments are supported, along with a range of
+familiar options from [git diff](https://git-scm.com/docs/git-diff#_options).
+
+* `npm diff <spec-a> <spec-b>`
+
+    Compares two package versions using their registry specifiers, e.g:
+    `npm diff foo@1.0.0 foo@^2.0.0`. It's also possible to compare across forks
+    of any package, e.g: `npm diff foo@1.0.0 foo-fork@1.0.0`.
+
+    Any valid spec can be used, so that it's also possible to compare
+    directories or git repositories, e.g: `npm diff foo@latest ./packages/foo`
+
+* `npm diff` (in a package directory, no arguments):
+
+    If the package is published to the registry, `npm diff` will fetch the
+    tarball version tagged as `latest` (this value can be configured using the
+    `tag` option) and proceed to compare the contents of files present in that
+    tarball, with the current files in your local file system.
+
+    This workflow provides a handy way for package authors to see what
+    package-tracked files have been changed in comparison with the latest
+    published version of that package.
+
+* `npm diff <version-a> [<version-b>]`
+
+    Using `npm diff` along with semver-valid version numbers is a shorthand
+    to compare different versions of the current package. It needs to be run
+    from a package directory, such that for a package named `foo` running
+    `npm diff 1.0.0 1.0.1` is the same as running
+    `npm diff foo@1.0.0 foo@1.0.1`. If only a single argument `<version-a>` is
+    provided, then the current local file system is going to be compared
+    against that version.
+
+* `npm diff <pkg-name>`
+
+    When using a single package name (with no version or tag specifier) as an
+    argument, `npm diff` will work in a similar way to
+    [`npm-outdated`](npm-outdated) and reach for the registry to figure out
+    what current published version of the package named <pkg-name> will satisfy
+    its dependent declared semver-range. Once that specific version is known
+    `npm diff` will print diff patches comparing the current version of
+    <pkg-name> found in the local file system with that specific version
+    returned by the registry.
+
+* `npm diff <spec-a>` (single specifier argument)
+
+    Similar to using only a single package name, it's also possible to declare
+    a full registry specifier version if you wish to compare the local version
+    of a installed package with the specific version/tag/semver-range provided
+    in `<spec-a>`. e.g: (assuming foo@1.0.0 is installed in the current
+    `node_modules` folder) running `npm diff foo@2.0.0` will effectively be
+    an alias to `npm diff foo@1.0.0 foo@2.0.0`.
+
+#### Filtering files
+
+It's possible to also specify file names or globs pattern matching in order to
+limit the result of diff patches to only a subset of files for a given package.
+
+Given the fact that paths are also valid specs, a separator `--` is required
+when specifying sets of files to filter in diff. Any extra argument declared
+after `--` will be treated as a filenames/globs and diff results will be
+limited to files included or matched by those. e.g:
+
+`npm diff foo@2 -- lib/* CHANGELOG.md`
+
+Note: When using `npm diff` with two spec/version arguments, the separator `--`
+becomes redudant and can be removed, e.g: `npm diff foo@1.0.0 foo@1.0.1 lib/*`
+
+### Configuration
+
+#### name-only
+
+* Type: Boolean
+* Default: false
+
+When set to `true` running `npm diff` only returns the names of the files that
+have any difference.
+
+#### unified
+
+* Alias: `-U`
+* Type: number
+* Default: `3`
+
+The number of lines of context to print in the unified diff format output.
+
+#### ignore-all-space
+
+* Alias: `-w`
+* Type: Boolean
+* Default: false
+
+Ignore whitespace when comparing lines. This ignores differences even if one
+line has whitespace where the other line has none.
+
+#### no-prefix
+
+* Type: Boolean
+* Default: false
+
+Do not show any source or destination prefix.
+
+#### src-prefix
+
+* Type: String
+* Default: `"a/"`
+
+Show the given source prefix in diff patches headers instead of using "a/".
+
+#### dst-prefix
+
+* Type: String
+* Default: `"b/"`
+
+Show the given source prefix in diff patches headers instead of using "b/".
+
+#### text
+
+* Alias: `-a`
+* Type: Boolean
+* Default: false
+
+Treat all files as text.
+
+#### tag
+
+* Type: String
+* Default: `"latest"`
+
+The tag used to fetch the tarball that will be compared with local file system
+files when running npm diff with no arguments.
+
+
+## See Also
+
+* [npm outdated](/commands/npm-outdated)
+* [npm install](/commands/npm-install)
+* [npm config](/commands/npm-config)
+* [npm registry](/using-npm/registry)

lib/diff.js

@@ -0,0 +1,200 @@
+const semver = require('semver')
+const libdiff = require('libnpmdiff')
+const npa = require('npm-package-arg')
+const Arborist = require('@npmcli/arborist')
+const npmlog = require('npmlog')
+const pacote = require('pacote')
+const pickManifest = require('npm-pick-manifest')
+
+const npm = require('./npm.js')
+const usageUtil = require('./utils/usage.js')
+const output = require('./utils/output.js')
+const completion = require('./utils/completion/none.js')
+const readLocalPkg = require('./utils/read-local-package.js')
+
+const usage = usageUtil(
+  'diff',
+  'npm diff' +
+  '\nnpm diff [--ignore-all-space] [--name-only] [-- <path>...]' +
+  '\nnpm diff <pkg-name>' +
+  '\nnpm diff <version-a> [<version-b>]' +
+  '\nnpm diff <spec-a> [<spec-b>]'
+)
+
+const cmd = (args, cb) => diff(args).then(() => cb()).catch(cb)
+
+const diff = async (args) => {
+  const [a, b, ...files] = parseArgs(args)
+  const specs = await retrieveSpecs([a, b])
+  npmlog.info(`diff a:${specs.a} b:${specs.b}`)
+  const res = await libdiff(specs, {
+    ...npm.flatOptions,
+    ...{ diffOpts: {
+      files,
+      ...getDiffOpts(),
+    }},
+  })
+  return output(res)
+}
+
+const parseArgs = (args) => {
+  const argv = npm.config.parsedArgv.cooked
+  const sep = argv.indexOf('--')
+
+  if (sep > -1) {
+    const files = argv.slice(sep + 1)
+    const notFiles = argv.slice(0, sep)
+    const [a, b] = args.map(arg => notFiles.includes(arg) ? arg : undefined)
+    return [a, b, ...files]
+  }
+
+  return args
+}
+
+const retrieveSpecs = async (args) => {
+  const [a, b] = await convertVersionsToSpecs(args)
+
+  if (!a) {
+    const spec = await defaultSpec()
+    return { a: spec }
+  }
+
+  if (!b)
+    return await transformSingleSpec(a)
+
+  return { a, b }
+}
+
+const convertVersionsToSpecs = (args) =>
+  Promise.all(args.map(async arg => {
+    if (semver.valid(arg)) {
+      let pkgName
+      try {
+        pkgName = await readLocalPkg()
+      } catch (e) {}
+
+      if (!pkgName) {
+        throw new Error(
+          'Needs to be run from a project dir in order to use versions.\n\n' +
+          `Usage:\n${usage}`
+        )
+      }
+
+      return `${pkgName}@${arg}`
+    }
+    return arg
+  }))
+
+const defaultSpec = async () => {
+  let pkgName
+  try {
+    pkgName = await readLocalPkg()
+  } catch (e) {}
+
+  if (!pkgName) {
+    throw new Error(
+      'Needs multiple arguments to compare or run from a project dir.\n\n' +
+      `Usage:\n${usage}`
+    )
+  }
+
+  return `${pkgName}@${npm.flatOptions.defaultTag}`
+}
+
+const transformSingleSpec = async (a) => {
+  const spec = npa(a)
+  let pkgName
+
+  try {
+    pkgName = await readLocalPkg()
+  } catch (e) {}
+
+  if (!pkgName) {
+    throw new Error(
+      'Needs to be run from a project dir in order to use a single package name.\n\n' +
+      `Usage:\n${usage}`
+    )
+  }
+
+  // when using a single package name as arg and it's part of the current
+  // install tree, then retrieve the current installed version and compare
+  // it against the same value `npm outdated` would suggest you to update to
+  if (spec.registry && spec.name !== pkgName) {
+    const opts = {
+      ...npm.flatOptions,
+      path: npm.flatOptions.prefix,
+    }
+    const arb = new Arborist(opts)
+    const actualTree = await arb.loadActual(opts)
+    const [node] = [
+      ...actualTree.inventory
+        .query('name', spec.name)
+        .values(),
+    ]
+
+    if (!node || !node.name || !node.package || !node.package.version) {
+      throw new Error(
+        `Package ${a} not found in the current installed tree.\n\n` +
+        `Usage:\n${usage}`
+      )
+    }
+
+    const tryRootNodeSpec = () =>
+      (actualTree.edgesOut.get(spec.name) || {}).spec
+
+    const tryAnySpec = () => {
+      for (const edge of node.edgesIn)
+        return edge.spec
+    }
+
+    const aSpec = node.package.version
+
+    // finds what version of the package to compare against, if a exact
+    // version or tag was passed than it should use that, otherwise
+    // work from the top of the arborist tree to find the original semver
+    // range declared in the package that depends on the package.
+    let bSpec
+    if (spec.rawSpec)
+      bSpec = spec.rawSpec
+    else {
+      const bTargetVersion =
+        tryRootNodeSpec()
+        || tryAnySpec()
+        || `${npm.flatOptions.savePrefix}${node.package.version}`
+
+      // figure out what to compare against,
+      // follows same logic to npm outdated "Wanted" results
+      const packument = await pacote.packument(spec, {
+        ...npm.flatOptions,
+        preferOnline: true,
+      })
+      bSpec = pickManifest(
+        packument,
+        bTargetVersion,
+        { ...npm.flatOptions }
+      ).version
+    }
+
+    return {
+      a: `${spec.name}@${aSpec}`,
+      b: `${spec.name}@${bSpec}`,
+    }
+  }
+
+  return { a }
+}
+
+const getDiffOpts = () => ({
+  nameOnly: npm.config.get('name-only', 'cli'),
+  context: npm.config.get('unified', 'cli') ||
+    npm.config.get('U', 'cli'),
+  ignoreWhitespace: npm.config.get('ignore-all-space', 'cli') ||
+    npm.config.get('w', 'cli'),
+  noPrefix: npm.config.get('no-prefix', 'cli'),
+  srcPrefix: npm.config.get('src-prefix', 'cli'),
+  dstPrefix: npm.config.get('dst-prefix', 'cli'),
+  text: npm.config.get('text', 'cli') ||
+    npm.config.get('a', 'cli'),
+})
+
+module.exports = Object.assign(cmd, { completion, usage })

lib/utils/cmd-list.js

@@ -119,6 +119,7 @@ const cmdList = [
   'prefix',
   'bin',
   'whoami',
+  'diff',
   'dist-tag',
   'ping',