poetry run: deprecate uninstalled entry points

src/poetry/console/commands/run.py

@@ -63,6 +63,9 @@ def run_script(self, script: str | dict[str, str], args: list[str]) -> int:
             if script_path.exists():
                 args = [str(script_path), *args[1:]]
                 break
+        else:
+            # If reach this point, the script is not installed
+            self._warning_not_installed_script(args[0])
 
         if isinstance(script, dict):
             script = script["callable"]
@@ -81,3 +84,27 @@ def run_script(self, script: str | dict[str, str], args: list[str]) -> int:
         ]
 
         return self.env.execute(*cmd)
+
+    def _warning_not_installed_script(self, script: str) -> None:
+        self.line_error(
+            (
+                f"Warning: '{script}' is an entry point defined in pyproject.toml,"
+                " but it's not installed as a script."
+                " You may get improper `sys.argv[0]`."
+            ),
+            style="warning",
+        )
+        self.line_error("")
+        self.line_error(
+            (
+                "The support to run uninstalled scripts "
+                "will be removed in a future release."
+            ),
+            style="warning",
+        )
+        self.line_error("")
+        self.line_error(
+            "Run `poetry install` to resolve and get rid of this message.",
+            style="warning",
+        )
+        self.line_error("")

tests/console/commands/test_run.py

@@ -171,12 +171,15 @@ def test_run_script_sys_argv0(
         environment=tmp_venv,
     )
     assert install_tester.execute() == 0
-    if not installed_script:
-        for path in tmp_venv.script_dirs[0].glob("check-argv0*"):
+
+    script = "check-argv0"
+    if installed_script:
+        script = tmp_venv.script_dirs[0] / script
+    else:
+        for path in tmp_venv.script_dirs[0].glob(script + "*"):
             path.unlink()
 
     tester = command_tester_factory(
         "run", poetry=poetry_with_scripts, environment=tmp_venv
     )
-    argv1 = "absolute" if installed_script else "relative"
-    assert tester.execute(f"check-argv0 {argv1}") == 0
+    assert tester.execute(f"check-argv0 {script}") == 0

tests/fixtures/scripts/scripts/check_argv0.py

@@ -7,14 +7,13 @@
 
 def main() -> int:
     path = Path(sys.argv[0])
-    if sys.argv[1] == "absolute":
-        if not path.is_absolute():
-            raise RuntimeError(f"sys.argv[0] is not an absolute path: {path}")
-        if not path.exists():
+    if sys.argv[0] == sys.argv[1]:
+        if path.is_absolute() and not path.exists():
             raise RuntimeError(f"sys.argv[0] does not exist: {path}")
     else:
-        if path.is_absolute():
-            raise RuntimeError(f"sys.argv[0] is an absolute path: {path}")
+        raise RuntimeError(
+            f"unexpected sys.argv[0]: '{sys.argv[0]}', should be '{sys.argv[1]}'"
+        )
 
     return 0