Allow setting default args for commands / callbacks (#157)

Allows overriding the default keyword arguments passed to commands.
E.g., consider:

```python
@click.command()
@click.option("-f", "--flag")
@click.option("-t", "--test", default="not set")
def example(flag, test, default_kwd=None):
```
```toml
[tool.spin.kwargs]
".spin/cmds.py:example" = {"test" = "default override", "default_kwd" = 3}
```
This will override the `--test` flag's default value to `default override`.
It will also override the `default_kwd` keyword, which is not associated
with a flag.

Author: stefanv

README.md

@@ -147,6 +147,29 @@ def example():
     print(config["tool.spin"])
 ```
 
+### Argument overrides
+
+Default arguments can be overridden for any command.
+The custom command above, e.g., has the following signature:
+
+```python
+@click.command()
+@click.option("-f", "--flag")
+@click.option("-t", "--test", default="not set")
+def example(flag, test, default_kwd=None):
+    """🧪 Example custom command.
+    ...
+    """
+```
+
+Use the `[tool.spin.kwargs]` section to override default values for
+click options or function keywords:
+
+```toml
+[tool.spin.kwargs]
+".spin/cmds.py:example" = {"test" = "default override", "default_kwd" = 3}
+```
+
 ### Advanced: adding arguments to built-in commands
 
 Instead of rewriting a command from scratch, a project may want to add a flag to a built-in `spin` command, or perhaps do some pre- or post-processing.

example_pkg/.spin/cmds.py

@@ -7,7 +7,8 @@
 
 @click.command()
 @click.option("-f", "--flag")
-def example(flag):
+@click.option("-t", "--test", default="not set")
+def example(flag, test, default_kwd=None):
     """🧪 Example custom command.
 
     Accepts arbitrary flags, and shows how to access `pyproject.toml`
@@ -20,6 +21,11 @@ def example(flag):
     click.secho("Flag provided with --flag is: ", fg="yellow", nl=False)
     print(flag or None)
 
+    click.secho("Flag provided with --test is: ", fg="yellow", nl=False)
+    print(test or None)
+
+    click.secho(f"Default kwd is: {default_kwd}")
+
     click.secho("\nDefined commands:", fg="yellow")
     for section in commands:
         print(f"  {section}: ", end="")

example_pkg/pyproject.toml

@@ -48,3 +48,6 @@ package = 'example_pkg'
 "Install" = [
   "spin.cmds.pip.install"
 ]
+
+[tool.spin.kwargs]
+".spin/cmds.py:example" = {"test" = "default override", "default_kwd" = 3}

spin/__main__.py

@@ -94,6 +94,7 @@ def group(ctx):
         "spin.python": _cmds.meson.python,
         "spin.shell": _cmds.meson.shell,
     }
+    cmd_default_kwargs = toml_config.get("tool.spin.kwargs", {})
 
     for section, cmds in config_cmds.items():
         for cmd in cmds:
@@ -133,6 +134,18 @@ def group(ctx):
                     print(f"!! Could not load command `{func}` from file `{path}`.\n")
                     continue
 
+                default_kwargs = cmd_default_kwargs.get(cmd)
+                import functools
+
+                if default_kwargs:
+                    callback = cmd_func.callback
+                    cmd_func.callback = functools.partial(callback, **default_kwargs)
+
+                    # Also override option defaults
+                    for option in cmd_func.params:
+                        if option.name in default_kwargs:
+                            option.default = default_kwargs[option.name]
+
                 commands[cmd] = cmd_func
 
             group.add_command(commands[cmd], section=section)

spin/tests/test_build_cmds.py

@@ -4,41 +4,10 @@
 import tempfile
 from pathlib import Path
 
-import pytest
+from testutil import skip_on_windows, skip_unless_linux, spin, stdout
 
-import spin as libspin
 from spin.cmds.util import run
 
-skip_on_windows = pytest.mark.skipif(
-    sys.platform.startswith("win"), reason="Skipped; platform is Windows"
-)
-
-on_linux = pytest.mark.skipif(
-    not sys.platform.startswith("linux"), reason="Skipped; platform not Linux"
-)
-
-
-def spin(*args, **user_kwargs):
-    default_kwargs = {
-        "stdout": subprocess.PIPE,
-        "stderr": subprocess.PIPE,
-        "sys_exit": True,
-    }
-    return run(["spin"] + list(args), **{**default_kwargs, **user_kwargs})
-
-
-def stdout(p):
-    return p.stdout.decode("utf-8").strip()
-
-
-def stderr(p):
-    return p.stderr.decode("utf-8").strip()
-
-
-def test_get_version():
-    p = spin("--version")
-    assert stdout(p) == f"spin {libspin.__version__}"
-
 
 def test_basic_build():
     """Does the package build?"""
@@ -145,7 +114,7 @@ def test_spin_install():
             run(["pip", "uninstall", "-y", "--quiet", "example_pkg"])
 
 
-@on_linux
+@skip_unless_linux
 def test_gdb():
     p = spin(
         "gdb",

spin/tests/test_cli.py

@@ -0,0 +1,17 @@
+from testutil import spin, stdout
+
+import spin as libspin
+
+
+def test_get_version():
+    p = spin("--version")
+    assert stdout(p) == f"spin {libspin.__version__}"
+
+
+def test_arg_override():
+    p = spin("example")
+    assert "--test is: default override" in stdout(p)
+    assert "Default kwd is: 3" in stdout(p)
+
+    p = spin("example", "-t", 6)
+    assert "--test is: 6" in stdout(p)

spin/tests/testutil.py

@@ -0,0 +1,32 @@
+import subprocess
+import sys
+
+import pytest
+
+from spin.cmds.util import run
+
+skip_on_windows = pytest.mark.skipif(
+    sys.platform.startswith("win"), reason="Skipped; platform is Windows"
+)
+
+skip_unless_linux = pytest.mark.skipif(
+    not sys.platform.startswith("linux"), reason="Skipped; platform not Linux"
+)
+
+
+def spin(*args, **user_kwargs):
+    args = (str(el) for el in args)
+    default_kwargs = {
+        "stdout": subprocess.PIPE,
+        "stderr": subprocess.PIPE,
+        "sys_exit": True,
+    }
+    return run(["spin"] + list(args), **{**default_kwargs, **user_kwargs})
+
+
+def stdout(p):
+    return p.stdout.decode("utf-8").strip()
+
+
+def stderr(p):
+    return p.stderr.decode("utf-8").strip()