feat: adds recommendCommands() for command suggestions (#580)

* feat: provide suggestions if unknown command is called

* add y18n locale support for command recommendations

* fix tests for command recommendations

* make german translation more personal

* update .recommendCommands() following @nexdrew's review

* add more tests for .recommendCommands()

* add didyoumean threshold

* mention in readme no parameter is required for .recommendCommands()

* fix silly mistake

* feat: adds recommendCommands()

* fix: implement @nexdrew's suggestion; sort commands so that we recommend longest first

README.md

@@ -1406,6 +1406,12 @@ as a configuration object.
 `cwd` can optionally be provided, the package.json will be read
 from this location.
 
+.recommendCommands()
+---------------------------
+
+Should yargs provide suggestions regarding similar commands if no matching
+command is found?
+
 .require(key, [msg | boolean])
 ------------------------------
 .required(key, [msg | boolean])

lib/levenshtein.js

@@ -0,0 +1,47 @@
+/*
+Copyright (c) 2011 Andrei Mackenzie
+
+Permission is hereby granted, free of charge, to any person obtaining a copy of this software and associated documentation files (the "Software"), to deal in the Software without restriction, including without limitation the rights to use, copy, modify, merge, publish, distribute, sublicense, and/or sell copies of the Software, and to permit persons to whom the Software is furnished to do so, subject to the following conditions:
+
+The above copyright notice and this permission notice shall be included in all copies or substantial portions of the Software.
+
+THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY, FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM, OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE SOFTWARE.
+*/
+
+// levenshtein distance algorithm, pulled from Andrei Mackenzie's MIT licensed.
+// gist, which can be found here: https://gist.github.com/andrei-m/982927
+
+// Compute the edit distance between the two given strings
+module.exports = function (a, b) {
+  if (a.length === 0) return b.length
+  if (b.length === 0) return a.length
+
+  var matrix = []
+
+  // increment along the first column of each row
+  var i
+  for (i = 0; i <= b.length; i++) {
+    matrix[i] = [i]
+  }
+
+  // increment each column in the first row
+  var j
+  for (j = 0; j <= a.length; j++) {
+    matrix[0][j] = j
+  }
+
+  // Fill in the rest of the matrix
+  for (i = 1; i <= b.length; i++) {
+    for (j = 1; j <= a.length; j++) {
+      if (b.charAt(i - 1) === a.charAt(j - 1)) {
+        matrix[i][j] = matrix[i - 1][j - 1]
+      } else {
+        matrix[i][j] = Math.min(matrix[i - 1][j - 1] + 1, // substitution
+                                Math.min(matrix[i][j - 1] + 1, // insertion
+                                         matrix[i - 1][j] + 1)) // deletion
+      }
+    }
+  }
+
+  return matrix[b.length][a.length]
+}

lib/validation.js

@@ -274,6 +274,23 @@ module.exports = function (yargs, usage, y18n) {
     }
   }
 
+  self.recommendCommands = function (cmd, potentialCommands) {
+    const distance = require('./levenshtein')
+    const threshold = 3 // if it takes more than three edits, let's move on.
+    potentialCommands = potentialCommands.sort(function (a, b) { return b.length - a.length })
+
+    var recommended = null
+    var bestDistance = Infinity
+    for (var i = 0, candidate; (candidate = potentialCommands[i]) !== undefined; i++) {
+      var d = distance(cmd, candidate)
+      if (d <= threshold && d < bestDistance) {
+        bestDistance = d
+        recommended = candidate
+      }
+    }
+    if (recommended) usage.fail(__('Did you mean %s?', recommended))
+  }
+
   self.reset = function (globalLookup) {
     implied = objFilter(implied, function (k, v) {
       return globalLookup[k]

locales/de.json

@@ -33,5 +33,6 @@
   "Invalid JSON config file: %s": "Fehlerhafte JSON-Config Datei: %s",
   "Path to JSON config file": "Pfad zur JSON-Config Datei",
   "Show help": "Hilfe anzeigen",
-  "Show version number": "Version anzeigen"
+  "Show version number": "Version anzeigen",
+  "Did you mean %s?": "Meintest du %s?"
 }

locales/en.json

@@ -33,5 +33,6 @@
   "Invalid JSON config file: %s": "Invalid JSON config file: %s",
   "Path to JSON config file": "Path to JSON config file",
   "Show help": "Show help",
-  "Show version number": "Show version number"
+  "Show version number": "Show version number",
+  "Did you mean %s?": "Did you mean %s?"
 }

test/yargs.js

@@ -261,6 +261,40 @@ describe('yargs dsl tests', function () {
         .argv
     })
 
+    it('recommends a similar command if no command handler is found', function () {
+      var r = checkOutput(function () {
+        yargs(['boat'])
+          .command('goat')
+          .recommendCommands()
+          .argv
+      })
+
+      r.errors[1].should.match(/Did you mean goat/)
+    })
+
+    it('does not recommend a similiar command if no similar command exists', function () {
+      var r = checkOutput(function () {
+        yargs(['foo'])
+          .command('nothingSimilar')
+          .recommendCommands()
+          .argv
+      })
+
+      r.logs.should.be.empty
+    })
+
+    it('recommends the longest match first', function () {
+      var r = checkOutput(function () {
+        yargs(['boat'])
+          .command('bot')
+          .command('goat')
+          .recommendCommands()
+          .argv
+      })
+
+      r.errors[1].should.match(/Did you mean goat/)
+    })
+
     it("skips executing top-level command if builder's help is executed", function () {
       var r = checkOutput(function () {
         yargs(['blerg', '-h'])

yargs.js

@@ -640,6 +640,12 @@ function Yargs (processArgs, cwd, parentRequire) {
     return detectLocale
   }
 
+  var recommendCommands
+  self.recommendCommands = function () {
+    recommendCommands = true
+    return self
+  }
+
   self.getUsageInstance = function () {
     return usage
   }
@@ -715,10 +721,21 @@ function Yargs (processArgs, cwd, parentRequire) {
       // if there's a handler associated with a
       // command defer processing to it.
       var handlerKeys = command.getCommands()
-      for (var i = 0, cmd; (cmd = argv._[i]) !== undefined; i++) {
-        if (~handlerKeys.indexOf(cmd) && cmd !== completionCommand) {
-          setPlaceholderKeys(argv)
-          return command.runCommand(cmd, self, parsed)
+      if (handlerKeys.length) {
+        var firstUnknownCommand
+        for (var i = 0, cmd; (cmd = argv._[i]) !== undefined; i++) {
+          if (~handlerKeys.indexOf(cmd) && cmd !== completionCommand) {
+            setPlaceholderKeys(argv)
+            return command.runCommand(cmd, self, parsed)
+          } else if (!firstUnknownCommand && cmd !== completionCommand) {
+            firstUnknownCommand = cmd
+          }
+        }
+
+        // recommend a command if recommendCommands() has
+        // been enabled, and no commands were found to execute
+        if (recommendCommands && firstUnknownCommand) {
+          validation.recommendCommands(firstUnknownCommand, handlerKeys)
         }
       }