Handle missing COMP_WORDS and COMP_CWORD in completion script

Author: orf

news/12401.bugfix.rst

@@ -0,0 +1 @@
+Fix exception with completions when COMP_CWORD is not set

src/pip/_internal/cli/autocompletion.py

@@ -17,6 +17,10 @@ def autocomplete() -> None:
     # Don't complete if user hasn't sourced bash_completion file.
     if "PIP_AUTO_COMPLETE" not in os.environ:
         return
+    # Don't complete if autocompletion environment variables
+    # are not present
+    if not os.environ.get("COMP_WORDS") or not os.environ.get("COMP_CWORD"):
+        return
     cwords = os.environ["COMP_WORDS"].split()[1:]
     cword = int(os.environ["COMP_CWORD"])
     try:

tests/functional/test_completion.py

@@ -128,7 +128,11 @@ def autocomplete_script(
 
 class DoAutocomplete(Protocol):
     def __call__(
-        self, words: str, cword: str, cwd: Union[Path, str, None] = None
+        self,
+        words: str,
+        cword: str,
+        cwd: Union[Path, str, None] = None,
+        include_env: bool = True,
     ) -> Tuple[TestPipResult, PipTestEnvironment]:
         ...
 
@@ -141,10 +145,14 @@ def autocomplete(
     autocomplete_script.environ["PIP_AUTO_COMPLETE"] = "1"
 
     def do_autocomplete(
-        words: str, cword: str, cwd: Union[Path, str, None] = None
+        words: str,
+        cword: str,
+        cwd: Union[Path, str, None] = None,
+        include_env: bool = True,
     ) -> Tuple[TestPipResult, PipTestEnvironment]:
-        autocomplete_script.environ["COMP_WORDS"] = words
-        autocomplete_script.environ["COMP_CWORD"] = cword
+        if include_env:
+            autocomplete_script.environ["COMP_WORDS"] = words
+            autocomplete_script.environ["COMP_CWORD"] = cword
         result = autocomplete_script.run(
             "python",
             "-c",
@@ -409,3 +417,16 @@ def test_completion_uses_same_executable_name(
         expect_stderr=deprecated_python,
     )
     assert executable_name in result.stdout
+
+
+def test_completion_without_env_vars(autocomplete: DoAutocomplete) -> None:
+    """
+    Test getting completion <path> after options in command
+    given absolute path
+    """
+    res, env = autocomplete(
+        words="pip install ",
+        cword="",
+        include_env=False,
+    )
+    assert res.stdout == ""