suggestions for unknown commands in subprocess mode

xonsh/built_ins.py

@@ -11,9 +11,9 @@ from io import TextIOWrapper, StringIO
 from glob import glob, iglob
 from subprocess import Popen, PIPE
 from contextlib import contextmanager
-from collections import Sequence, MutableMapping, Iterable, namedtuple
+from collections import Sequence, MutableMapping, Iterable, namedtuple, OrderedDict
 
-from xonsh.tools import string_types, redirect_stdout, redirect_stderr
+from xonsh.tools import string_types, redirect_stdout, redirect_stderr, levenshtein, levenshtein_sort_helper
 from xonsh.inspectors import Inspector
 from xonsh.environ import default_env
 from xonsh.aliases import DEFAULT_ALIASES
@@ -355,7 +355,34 @@ def run_subproc(cmds, captured=True):
             proc = Popen(aliased_cmd, universal_newlines=uninew, env=ENV.detype(),
                          stdin=stdin, stdout=stdout)
         except FileNotFoundError:
-            print('xonsh: subprocess mode: command not found: {0}'.format(aliased_cmd[0]))
+            cmd = aliased_cmd[0]
+            print('xonsh: subprocess mode: command not found: {0}'.format(cmd))
+            if(ENV.get('SUGGEST_COMMANDS', True)):
+                threshold = ENV.get('SUGGEST_ERROR_THRESHOLD', 3)
+                max_sugg = ENV.get('SUGGEST_MAX_NUM', 5)
+                if max_sugg < 0:
+                    max_sugg = float('inf')
+                suggested = {}
+                path = ENV.get('PATH',[])
+                for a in builtins.aliases:
+                    if a not in suggested and levenshtein(a, cmd) < threshold:
+                        suggested[a] = 'Alias'
+                for d in path:
+                    if os.path.isdir(d):
+                        for f in os.listdir(d):
+                            if f not in suggested and levenshtein(f, cmd) < threshold:
+                                fname = os.path.join(d,f)
+                                suggested[f] = 'Command ({0})'.format(fname)
+                suggested = OrderedDict(sorted(suggested.items(), 
+                                        key=lambda x: levenshtein_sort_helper(x[0], cmd)))
+                num = min(len(suggested), max_sugg)
+                if num>1:
+                    print('Did you mean one of the following?')
+                elif num>0:
+                    print('Did you mean the following?')
+                for i in range(num):
+                    k,v = suggested.popitem(False)
+                    print('    {0}: {1}'.format(k,v))
             return
         if prev_is_proxy:
             proc.communicate(input=prev_proc.stdout)

xonsh/tools.py

@@ -210,3 +210,34 @@ class redirect_stdout(_RedirectStream):
 class redirect_stderr(_RedirectStream):
     """Context manager for temporarily redirecting stderr to another file."""
     _stream = "stderr"
+
+
+# Public Domain code, by Magnus Lie Hetland
+# from http://hetland.org/coding/python/levenshtein.py 
+def levenshtein(a,b):
+    "Calculates the Levenshtein distance between a and b."
+    n, m = len(a), len(b)
+    if n > m:
+        # Make sure n <= m, to use O(min(n,m)) space
+        a,b = b,a
+        n,m = m,n
+        
+    current = range(n+1)
+    for i in range(1,m+1):
+        previous, current = current, [i]+[0]*n
+        for j in range(1,n+1):
+            add, delete = previous[j]+1, current[j-1]+1
+            change = previous[j-1]
+            if a[j-1] != b[i-1]:
+                change = change + 1
+            current[j] = min(add, delete, change)
+            
+    return current[n]
+
+def levenshtein_sort_helper(x, y):
+    x = x.lower()
+    y = y.lower()
+    lendiff = len(x)+len(y)
+    inx = len([i for i in x if i not in y])
+    iny = len([i for i in y if i not in x])
+    return lendiff + inx + iny