Fix using run with file descriptors

changelog.d/1293.bugfix.md

@@ -0,0 +1 @@
+Fix run command with bash substitution (e.g. `pipx run <(pbpaste)`)

src/pipx/commands/run.py

@@ -50,7 +50,11 @@ def maybe_script_content(app: str, is_path: bool) -> Optional[Union[str, Path]]:
     app_path = Path(app)
     if app_path.is_file():
         return app_path
-    elif is_path:
+    # In case it's a named pipe, read it out to pass to the interpreter
+    if app_path.is_fifo():
+        return app_path.read_text(encoding="utf-8")
+
+    if is_path:
         raise PipxError(f"The specified path {app} does not exist")
 
     # Check for a URL

tests/test_run.py

@@ -370,6 +370,35 @@ def test_run_script_by_relative_name(caplog, pipx_temp_env, monkeypatch, tmp_pat
     assert out.read_text() == test_str
 
 
+@mock.patch("os.execvpe", new=execvpe_mock)
+@pytest.mark.skipif(sys.platform.startswith("win"), reason="uses file descriptor")
+def test_run_script_by_file_descriptor(caplog, pipx_temp_env, monkeypatch, tmp_path):
+    read_fd, write_fd = os.pipe()
+    out = tmp_path / "output.txt"
+    test_str = "Hello, world!"
+
+    os.write(
+        write_fd,
+        textwrap.dedent(
+            f"""
+                from pathlib import Path
+                Path({repr(str(out))}).write_text({repr(test_str)})
+            """
+        )
+        .strip()
+        .encode("utf-8"),
+    )
+    os.close(write_fd)
+
+    with monkeypatch.context() as m:
+        m.chdir(tmp_path)
+        try:
+            run_pipx_cli_exit(["run", f"/dev/fd/{read_fd}"])
+        finally:
+            os.close(read_fd)
+    assert out.read_text() == test_str
+
+
 @pytest.mark.skipif(not sys.platform.startswith("win"), reason="uses windows version format")
 @mock.patch("os.execvpe", new=execvpe_mock)
 def test_run_with_windows_python_version(caplog, pipx_temp_env, tmp_path):