commands: add new generic --skip-if command line options

Previously, sambacc had the `--skip-if-file=` command line option that
would skip running a command if a named file exists. I have a need for
doing something similar for environment variable contents. In order to
avoid needing to add a plethora of new --skip-if-x type options over
time, add a more generic `--skip-if=` option and have the value contain
an initial prefix like `file:` or `env:` that determines how the rest of
the value will be parsed and how the skip will be determined (or not).
Deprecate `--skip-if-file`.

Maybe it's a case of over engineering, but at least it's easy to unit
test.

Examples:
* `--skip-if=env:CHAT==yes`, if the environment variable `CHAT` contains
  a value equal to "yes" the command will be skipped
* `--skip-if=file:/foo/bar` if the file `/foo/bar` exists the command
  will be skipped
* `--skip-if=file:!/foo/bar` if the file `/foo/bar` does not exist the command
  will be skipped
* `--skip-if=env:MODE!=777`, if the environment variable `MODE` contains
  a value not equal to "777" the command will be skipped
* `--skip-if=always:`, always skip this command (mainly to be used for
  testing/hacking on things)

Signed-off-by: John Mulligan <[email protected]>

Author: phlogistonjohn

sambacc/commands/dcmain.py

@@ -19,10 +19,10 @@
 import typing
 
 from . import addc
+from . import skips
 from .cli import Fail
 from .main import (
     CommandContext,
-    action_filter,
     enable_logging,
     env_to_cli,
     global_args,
@@ -41,9 +41,10 @@ def main(args: typing.Optional[typing.Sequence[str]] = None) -> None:
         raise Fail("missing container identity")
 
     pre_action(cli)
-    skip = action_filter(cli)
+    ctx = CommandContext(cli)
+    skip = skips.test(ctx)
     if skip:
-        print(f"Action skipped: {skip}")
+        print(f"Command Skipped: {skip}")
         return
     cfunc = getattr(cli, "cfunc", default_cfunc)
     cfunc(CommandContext(cli))

sambacc/commands/main.py

@@ -36,6 +36,7 @@
 from . import initialize  # noqa: F401
 from . import join  # noqa: F401
 from . import run  # noqa: F401
+from . import skips
 from . import users  # noqa: F401
 from .cli import commands, Fail, Parser
 
@@ -98,10 +99,23 @@ def global_args(parser: Parser) -> None:
         "--samba-command-prefix",
         help="Wrap samba commands within a supplied command prefix",
     )
+    parser.add_argument(
+        "--skip-if",
+        dest="skip_conditions",
+        action="append",
+        type=skips.parse,
+        help=(
+            "Skip execution based on a condition. Conditions include"
+            " 'file:<path>', 'env:<var>(==|!=)<value>', and 'always:'."
+            " (Pass `?` for more details)"
+        ),
+    )
     parser.add_argument(
         "--skip-if-file",
         action="append",
-        help="Perform no action if the specified path exists.",
+        dest="skip_conditions",
+        type=skips.SkipFile.parse,
+        help="(DEPRECATED) Perform no action if the specified path exists.",
     )
     parser.add_argument(
         "--validate-config",
@@ -309,13 +323,6 @@ def enable_logging(cli: typing.Any) -> None:
     logger.addHandler(handler)
 
 
-def action_filter(cli: typing.Any) -> typing.Optional[str]:
-    for path in cli.skip_if_file or []:
-        if os.path.exists(path):
-            return f"skip-if-file: {path} exists"
-    return None
-
-
 def main(args: typing.Optional[typing.Sequence[str]] = None) -> None:
     cli = commands.assemble(arg_func=global_args).parse_args(args)
     env_to_cli(cli)
@@ -324,12 +331,13 @@ def main(args: typing.Optional[typing.Sequence[str]] = None) -> None:
         raise Fail("missing container identity")
 
     pre_action(cli)
-    skip = action_filter(cli)
+    ctx = CommandContext(cli)
+    skip = skips.test(ctx)
     if skip:
-        print(f"Action skipped: {skip}")
+        print(f"Command Skipped: {skip}")
         return
     cfunc = getattr(cli, "cfunc", default_cfunc)
-    cfunc(CommandContext(cli))
+    cfunc(ctx)
     return