fix: same interpreter from venv to get pkg name (#957)

CHANGELOG.md

@@ -1,6 +1,7 @@
 ## dev
 
 - Fallback to user's log path if the default log path (`$PIPX_HOME/logs`) is not writable to aid with pipx being used for multi-user (e.g. system-wide) installs of applications
+- Fix wrong interpreter usage when injecting local pip-installable dependencies into venvs
 
 ## 1.2.0
 

src/pipx/commands/inject.py

@@ -1,3 +1,4 @@
+import os
 import sys
 from pathlib import Path
 from typing import List, Optional
@@ -47,7 +48,10 @@ def inject_dep(
     #   zip file, or tar.gz file.
     if package_name is None:
         package_name = package_name_from_spec(
-            package_spec, venv.python, pip_args=pip_args, verbose=verbose
+            package_spec,
+            os.fspath(venv.python_path),
+            pip_args=pip_args,
+            verbose=verbose,
         )
 
     venv.install_package(