fix: add support for {pdm} placeholder in scripts (#2408)

* add support for `{pdm}` placeholder in scripts

* check should_interpolate

* fix docs

* add news item

* Fix feedback and Windows

docs/docs/usage/scripts.md

@@ -243,6 +243,31 @@ $ pdm run test
     `call` scripts don't support the `{args}` placeholder as they have
     access to `sys.argv` directly to handle such complexe cases and more.
 
+### `{pdm}` placeholder
+
+Sometimes you may have multiple PDM installations, or `pdm` installed with a different name. This
+could for example occur in a CI/CD situation, or when working with different PDM versions in
+different repos. To make your scripts more robust you can use `{pdm}` to use the PDM entrypoint
+executing the script. This will expand to `{sys.executable} -m pdm`.
+
+```toml
+[tool.pdm.scripts]
+whoami = { shell = "echo `{pdm} -V` was called as '{pdm} -V'" }
+```
+will produce the following output:
+```shell
+$ pdm whoami
+PDM, version 0.1.dev2501+g73651b7.d20231115 was called as /usr/bin/python3 -m pdm -V
+
+$ pdm2.8 whoami
+PDM, version 2.8.0 was called as <snip>/venvs/pdm2-8/bin/python -m pdm -V
+```
+
+!!! note
+    While the above example uses PDM 2.8, this functionality was introduced in the 2.10 series and only backported for the showcase.
+
+
+
 ## Show the List of Scripts
 
 Use `pdm run --list/-l` to show the list of available script shortcuts:

news/2408.feature.md

@@ -0,0 +1 @@
+Add support for {pdm} placeholder in script definitions to call the same PDM entrypoint

src/pdm/cli/commands/run.py

@@ -8,6 +8,7 @@
 import signal
 import subprocess
 import sys
+from pathlib import Path
 from types import FrameType
 from typing import TYPE_CHECKING, Mapping, NamedTuple, Sequence, cast
 
@@ -44,9 +45,10 @@ def exec_opts(*options: TaskOptions | None) -> dict[str, Any]:
 
 
 RE_ARGS_PLACEHOLDER = re.compile(r"{args(?::(?P<default>[^}]*))?}")
+RE_PDM_PLACEHOLDER = re.compile(r"{pdm}")
 
 
-def interpolate(script: str, args: Sequence[str]) -> tuple[str, bool]:
+def _interpolate_args(script: str, args: Sequence[str]) -> tuple[str, bool]:
     """Interpolate the `{args:[defaults]} placeholder in a string"""
     import shlex
 
@@ -58,6 +60,25 @@ def replace(m: re.Match[str]) -> str:
     return interpolated, count > 0
 
 
+def _interpolate_pdm(script: str) -> str:
+    """Interpolate the `{pdm} placeholder in a string"""
+    executable_path = Path(sys.executable)
+
+    def replace(m: re.Match[str]) -> str:
+        return sh_join([executable_path.as_posix(), "-m", "pdm"])
+
+    interpolated = RE_PDM_PLACEHOLDER.sub(replace, script)
+    return interpolated
+
+
+def interpolate(script: str, args: Sequence[str]) -> tuple[str, bool]:
+    """Interpolate the `{args:[defaults]} placeholder in a string"""
+
+    script, args_interpolated = _interpolate_args(script, args)
+    script = _interpolate_pdm(script)
+    return script, args_interpolated
+
+
 class Task(NamedTuple):
     kind: str
     name: str
@@ -251,6 +272,7 @@ def run_task(self, task: Task, args: Sequence[str] = (), opts: TaskOptions | Non
         if kind == "composite":
             args = list(args)
             should_interpolate = any(RE_ARGS_PLACEHOLDER.search(script) for script in value)
+            should_interpolate = should_interpolate or any(RE_PDM_PLACEHOLDER.search(script) for script in value)
             code = 0
             for script in value:
                 if should_interpolate:

tests/cli/test_run.py

@@ -308,6 +308,20 @@ def test_run_script_with_args_placeholder_with_default(project, pdm, capfd, scri
     assert out.strip().splitlines()[1:] == expected
 
 
+def test_run_shell_script_with_pdm_placeholder(project, pdm):
+    project.pyproject.settings["scripts"] = {
+        "test_script": {
+            "shell": "{pdm} -V > output.txt",
+            "help": "test it won't fail",
+        }
+    }
+    project.pyproject.write()
+    with cd(project.root):
+        result = pdm(["run", "test_script"], obj=project)
+    assert result.exit_code == 0
+    assert (project.root / "output.txt").read_text().strip().startswith("PDM, version")
+
+
 def test_run_expand_env_vars(project, pdm, capfd, monkeypatch):
     (project.root / "test_script.py").write_text("import os; print(os.getenv('FOO'))")
     project.pyproject.settings["scripts"] = {