Add command suggestions feature

Author: krepysh

invoke/program.py

@@ -1,3 +1,4 @@
+import difflib
 import getpass
 import inspect
 import json
@@ -86,6 +87,12 @@ def core_args(self) -> List["Argument"]:
                 default=False,
                 help="Echo executed commands before running.",
             ),
+            Argument(
+                names=("suggestions", "s"),
+                kind=bool,
+                default=True,
+                help="Show possible commands suggestions.",
+            ),
             Argument(
                 names=("help", "h"),
                 optional=True,
@@ -403,6 +410,11 @@ def run(self, argv: Optional[List[str]] = None, exit: bool = True) -> None:
             # problems.
             if isinstance(e, ParseError):
                 print(e, file=sys.stderr)
+                if self.args.suggestions.value:
+                    unrecognised_cmd = str(e).replace("No idea what '", "")
+                    unrecognised_cmd = unrecognised_cmd.replace("' is!", "")
+                    msg = self._possible_commands_msg(unrecognised_cmd)
+                    print(msg, file=sys.stderr)
             if isinstance(e, Exit) and e.message:
                 print(e.message, file=sys.stderr)
             if isinstance(e, UnexpectedExit) and e.result.hide:
@@ -985,3 +997,23 @@ def print_columns(
             else:
                 print(spec.rstrip())
         print("")
+
+    def _possible_commands_msg(self, unknown_cmd: str) -> str:
+        try:
+            all_tasks = self.scoped_collection.task_names
+        except AttributeError:
+            all_tasks = {}
+
+        possible_cmds = list(all_tasks.keys())
+        suggestions = difflib.get_close_matches(
+            unknown_cmd, possible_cmds, n=3, cutoff=0.7
+        )
+        output_message = f"'{unknown_cmd}' is not an invoke command. "
+        output_message += "See 'invoke --list'.\n"
+        if suggestions:
+            output_message += "\nThe most similar command(s):\n"
+            for cmd in suggestions:
+                output_message += f"    {cmd}\n"
+        else:
+            output_message += "\nNo suggestions was found.\n"
+        return output_message

tests/program.py

@@ -41,6 +41,13 @@
 
 
 pytestmark = pytest.mark.usefixtures("integration")
+no_idea_what_template = """
+No idea what '{0}' is!
+'{0}' is not an invoke command. See 'invoke --list'.
+
+No suggestions was found.
+
+""".lstrip()
 
 
 class Program_:
@@ -360,7 +367,7 @@ def seeks_and_loads_tasks_module_by_default(self):
         def does_not_seek_tasks_module_if_namespace_was_given(self):
             expect(
                 "foo",
-                err="No idea what 'foo' is!\n",
+                err=no_idea_what_template.format("foo"),
                 program=Program(namespace=Collection("blank")),
             )
 
@@ -402,7 +409,7 @@ def ParseErrors_display_message_and_exit_1(self, mock_exit):
             # "no idea what foo is!") and exit 1. (Intent is to display that
             # info w/o a full traceback, basically.)
             stderr = sys.stderr.getvalue()
-            assert stderr == "No idea what '{}' is!\n".format(nah)
+            assert stderr == no_idea_what_template.format(nah)
             mock_exit.assert_called_with(1)
 
         @trap
@@ -599,6 +606,7 @@ def core_help_option_prints_core_help(self):
   -r STRING, --search-root=STRING    Change root directory used for finding
                                      task modules.
   -R, --dry                          Echo commands instead of running.
+  -s, --[no-]suggestions             Show possible commands suggestions.
   -T INT, --command-timeout=INT      Specify a global command execution
                                      timeout, in seconds.
   -V, --version                      Show version and exit.
@@ -736,7 +744,8 @@ def exits_after_printing(self):
                 expect("-c decorators -h punch --list", out=expected)
 
             def complains_if_given_invalid_task_name(self):
-                expect("-h this", err="No idea what 'this' is!\n")
+                expected = no_idea_what_template.format("this")
+                expect("-h this", err=expected)
 
     class task_list:
         "--list"