Subcommand help (#3956)

* change DvcParser to print subcommand help

* add tests for subcommand help

* docstring refactoring

* remote: finish separating RemoteTree methods (#3946)

* remote: move upload()/download() into tree

* remote: move path_info/path_cls into tree

* remote.azure: finish moving methods into tree

* remote.gs: finish moving methods into tree

* remote.hdfs: finish moving methods to tree

* remote.http: finish moving methods into tree

* remote.oss: finish moving methods into tree

* remote.s3: finish moving methods into tree

* remote.ssh: finish moving methods into tree

* remote.gdrive: finish moving methods into tree

* tests: update remote unit tests

* tests: update func tests

* remote: use walk_files() for all remotes

* list_cache_paths() now uses tree.walk_files() for all remotes except
  local/ssh

* fix DS warnings

* bugfixes

* Unify metrics behavior with dirs (#3935)

* run: disable directories for -m/-M flags

* run: reformatted string literals

* run: simplified metrics check

* tests: func: run: dirs as metrics outs

* tests: func: run: reformatted string literals

* tests: use pytest

Co-authored-by: Ruslan Kuprieiev <[email protected]>

* refactor/test multistage load for params and outputs (#3949)

* refactor multistage load for params and outputs

* tests: load params

* tests: output loading from pipeline file

* fix test

* fix typo in name

* split params load

* rename params func s/inject_values/fill_values

* fix tests

* simplify loads_params and output.load_from_pipeline

* address @pared's suggestions for tests

* remote: fix build errors (#3957)

* remote: fix remaining gdrive build issues (#3959)

* tests: fix gdrive build

* remote.gdrive: fix walk_files prefix relpath

* change DvcParser to print subcommand help

* add tests for subcommand help

* docstring refactoring

* change tests to pytest-style

* remove gettext

Co-authored-by: Peter Rowlands (변기호) <[email protected]>
Co-authored-by: nik123 <[email protected]>
Co-authored-by: Ruslan Kuprieiev <[email protected]>
Co-authored-by: Saugat Pachhai <[email protected]>

dvc/cli.py

@@ -81,18 +81,33 @@ COMMANDS = [
 class DvcParser(argparse.ArgumentParser):
     """Custom parser class for dvc CLI."""
 
-    def error(self, message):
+    def error(self, message, command=None):
         """Custom error method.
         Args:
             message (str): error message.
-
+            command (str): subcommand name for help message
         Raises:
             dvc.exceptions.DvcParser: dvc parser exception.
+
         """
         logger.error(message)
+        if command is not None:
+            for action in self._actions:
+                if action.dest == "cmd" and command in action.choices:
+                    subparser = action.choices[command]
+                    subparser.print_help()
+                    raise DvcParserError()
         self.print_help()
         raise DvcParserError()
 
+    # override this to send subcommand name to error method
+    def parse_args(self, args=None, namespace=None):
+        args, argv = self.parse_known_args(args, namespace)
+        if argv:
+            msg = "unrecognized arguments: %s"
+            self.error(msg % " ".join(argv), args.cmd)
+        return args
+
 
 class VersionAction(argparse.Action):  # pragma: no cover
     # pylint: disable=too-few-public-methods

tests/func/test_cli.py

@@ -12,7 +12,7 @@ from dvc.command.remove import CmdRemove
 from dvc.command.repro import CmdRepro
 from dvc.command.run import CmdRun
 from dvc.command.status import CmdDataStatus
-from dvc.exceptions import DvcException
+from dvc.exceptions import DvcException, DvcParserError
 from tests.basic_env import TestDvc
 
 
@@ -171,3 +171,36 @@ class TestFindRoot(TestDvc):
         args = A()
         with self.assertRaises(DvcException):
             CmdBase(args)
+
+
+def test_unknown_command_help(capsys):
+    try:
+        _ = parse_args(["unknown"])
+    except DvcParserError:
+        pass
+    captured = capsys.readouterr()
+    output = captured.out
+    try:
+        _ = parse_args(["--help"])
+    except SystemExit:
+        pass
+    captured = capsys.readouterr()
+    help_output = captured.out
+    assert output == help_output
+
+
+def test_unknown_subcommand_help(capsys):
+    sample_subcommand = "push"
+    try:
+        _ = parse_args([sample_subcommand, "--unknown"])
+    except DvcParserError:
+        pass
+    captured = capsys.readouterr()
+    output = captured.out
+    try:
+        _ = parse_args([sample_subcommand, "--help"])
+    except SystemExit:
+        pass
+    captured = capsys.readouterr()
+    help_output = captured.out
+    assert output == help_output