utils/cli: Introduce class to build CLI commands

Introduce a class allowing to programmatically generate CLI commands in
a clear, reliable and robust way for any calling code manipulating raw
command strings.

Author: pietos01-arm

devlib/utils/cli.py

@@ -0,0 +1,80 @@
+#    Copyright 2019 ARM Limited
+#
+# Licensed under the Apache License, Version 2.0 (the "License");
+# you may not use this file except in compliance with the License.
+# You may obtain a copy of the License at
+#
+#     http://www.apache.org/licenses/LICENSE-2.0
+#
+# Unless required by applicable law or agreed to in writing, software
+# distributed under the License is distributed on an "AS IS" BASIS,
+# WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+# See the License for the specific language governing permissions and
+# limitations under the License.
+#
+
+import collections
+import itertools
+import shlex
+
+class Command:
+    """Provides an abstraction for manipulating CLI commands
+    """
+    # pylint: disable=too-many-instance-attributes
+    # pylint: disable=too-few-public-methods
+    def __init__(self, command, flags=None, kwflags=None, kwflags_sep=' ',
+                 kwflags_join=',', options=None, end_of_options=None, args=None,
+                 stdout=None, stderr=None):
+        """
+        NB: if ``None`` in ``flags``, ``kwflags``, ``options``, replace with ``''``
+        empty flags are ignored
+        empty kwflag values are kept but striped
+        NB: caller responsible for escaping args as a single string
+        """ #TODO
+        # pylint: disable=too-many-arguments
+        these = lambda x: (x if isinstance(x, collections.abc.Iterable)
+                           and not isinstance(x, str) else [x])
+
+        self.command = shlex.split(command)
+        self.flags = map(str, filter(None, these(flags)))
+        self.kwflags_sep = kwflags_sep
+        self.kwflags_join = kwflags_join
+        self.kwflags = {} if kwflags is None else {
+            key: ['' if x is None else str(x) for x in these(values)]
+            for key, values in kwflags.items()
+        }
+        self.options = [] if options is None else [
+            '' if x is None else str(x) for x in these(options)]
+        if end_of_options:
+            self.options.append(str(end_of_options).strip())
+        if isinstance(args, collections.Mapping):
+            self.args = Command(**args)
+        else:
+            self.args = None if args is None else str(args)
+        self.stdout = stdout
+        self.stderr = stderr
+
+    def __str__(self):
+        filepipe = lambda f: (f if isinstance(f, str) and f.startswith('&')
+                              else shlex.quote(f))
+        quoted = itertools.chain(
+            self.command,
+            map(self._flagged, self.flags),
+            ('{}{}{}'.format(self._flagged(k),
+                             self.kwflags_sep,
+                             self.kwflags_join.join(v))
+             for k, v in self.kwflags.items()),
+            self.options
+        )
+        words = [shlex.quote(word) for word in quoted]
+        if self.args:
+            words.append(str(self.args))
+        if self.stdout:
+            words.append('1>{}'.format(filepipe(self.stdout)))
+        if self.stderr:
+            words.append('2>{}'.format(filepipe(self.stderr)))
+        return ' '.join(words)
+
+    @classmethod
+    def _flagged(cls, flag):
+        return '{}{}'.format('--' if len(flag) > 1 else '-', str(flag).strip())