optimize output configuration

treevalue/entry/cli/graph.py

@@ -4,6 +4,7 @@ import os
 import pickle
 import shutil
 import tempfile
+import warnings
 from functools import partial
 from itertools import chain
 from string import Template
@@ -14,7 +15,7 @@ import dill
 from graphviz import Digraph
 
 from .base import CONTEXT_SETTINGS
-from .utils import _multiple_validator, _EXPECTED_TREE_ERRORS
+from .utils import _multiple_validator, _EXPECTED_TREE_ERRORS, _click_pending
 from ...tree import TreeValue, load, graphics
 from ...utils import dynamic_call, post_process
 
@@ -139,13 +140,16 @@ def _save_image(g: Digraph, path: str, fmt: str):
 _IMAGE_FMTS = {'svg', 'png'}
 
 
-def _save_graph(g: Digraph, path: str, fmt: Optional[str] = None):
-    path = os.path.abspath(path)
+def _save_graph_fmt_infer(path: str, fmt: Optional[str] = None):
     if not fmt:
         _basename, _extname = os.path.splitext(path)
         if _extname:
             fmt = _extname[1:]
+    return fmt if fmt else None
+
 
+def _save_graph(g: Digraph, path: str, fmt: str):
+    path = os.path.abspath(path)
     _saver = partial(_save_image, fmt=fmt) if fmt in _IMAGE_FMTS else _save_source_code
     return _saver(g, path)
 
@@ -195,8 +199,14 @@ def _graph_cli(cli: click.Group):
         )
 
         if print_to_stdout:
+            if outputs:
+                warnings.warn(RuntimeWarning('The output destinations in -o options '
+                                             'will be ignored due to the enablement of -O option.'))
             click.echo(g.source)
-        for output in outputs:
-            _save_graph(g, output, fmt)
+        else:
+            for output in outputs:
+                _fmt = _save_graph_fmt_infer(output, fmt)
+                with _click_pending(f'Exporting graph to {repr(output)} as format {repr(_fmt)} ... '):
+                    _save_graph(g, output, _fmt)
 
     return cli

treevalue/entry/cli/utils.py

+from contextlib import contextmanager
 from functools import wraps
+from typing import Callable, Union
 
 import click
 
@@ -47,3 +49,28 @@ def _build_cli(base_cli, *wrappers):
     for wrapper in wrappers:
         _cli = wrapper(_cli or base_cli)
     return _cli
+
+
+@contextmanager
+def _click_pending(text: str, ok: Union[Callable, str] = 'OK', error: Union[Callable, str] = 'ERROR'):
+    if not hasattr(ok, '__call__'):
+        _okay_text = str(ok)
+        ok = lambda: _okay_text
+    ok = dynamic_call(ok)
+
+    if not hasattr(error, '__call__'):
+        _error_text = str(error)
+        error = lambda: _error_text
+    error = dynamic_call(error)
+
+    click.echo(text, nl=False)
+
+    try:
+        yield
+    except BaseException as err:
+        click.secho(click.style(error(err), fg='red'), nl=False)
+        raise err
+    else:
+        click.secho(click.style(ok(), fg='green'), nl=False)
+    finally:
+        click.echo('.', nl=True)