Refactor the handling of shellingham lazy-loading

pyproject.toml

@@ -209,8 +209,10 @@ known-first-party = ["reigns", "towns", "lands", "items", "users"]
 keep-runtime-typing = true
 
 [tool.ruff.lint.flake8-tidy-imports]
-# Import rich_utils from within functions (lazy), not at the module level (TID253)
-banned-module-level-imports = ["typer.rich_utils"]
+# Import rich_utils and shellingham from within functions (lazy),
+# not at the module level (TID253)
+banned-module-level-imports = ["typer.rich_utils", "shellingham"]
 
 [tool.ruff.lint.flake8-tidy-imports.banned-api]
 "rich".msg = "Use 'typer.rich_utils' instead of importing from 'rich' directly."
+"shellingham.detect_shell".msg = "Use 'typer._completion_shared._get_shell_name' instead of using 'shellingham.detect_shell' directly."

tests/test_completion/test_completion_install.py

@@ -4,7 +4,6 @@
 from pathlib import Path
 from unittest import mock
 
-import shellingham
 import typer
 from typer.testing import CliRunner
 
@@ -141,6 +140,8 @@ def test_completion_install_fish():
 
 @requires_completion_permission
 def test_completion_install_powershell():
+    import shellingham
+
     completion_path: Path = (
         Path.home() / ".config/powershell/Microsoft.PowerShell_profile.ps1"
     )

tests/test_completion/test_completion_show.py

@@ -3,7 +3,6 @@
 import sys
 from unittest import mock
 
-import shellingham
 import typer
 from typer.testing import CliRunner
 
@@ -142,6 +141,8 @@ def test_completion_source_pwsh():
 
 
 def test_completion_show_invalid_shell():
+    import shellingham
+
     with mock.patch.object(
         shellingham, "detect_shell", return_value=("xshell", "/usr/bin/xshell")
     ):

tests/test_others.py

@@ -7,7 +7,6 @@
 
 import click
 import pytest
-import shellingham
 import typer
 import typer.completion
 from typer.core import _split_opt
@@ -78,6 +77,8 @@ def convert(
 
 @requires_completion_permission
 def test_install_invalid_shell():
+    import shellingham
+
     app = typer.Typer()
 
     @app.command()

tests/utils.py

@@ -2,18 +2,7 @@
 from os import getenv
 
 import pytest
-
-try:
-    import shellingham
-    from shellingham import ShellDetectionFailure
-
-    shell = shellingham.detect_shell()[0]
-except ImportError:  # pragma: no cover
-    shellingham = None
-    shell = None
-except ShellDetectionFailure:  # pragma: no cover
-    shell = None
-
+from typer._completion_shared import _get_shell_name
 
 needs_py310 = pytest.mark.skipif(
     sys.version_info < (3, 10), reason="requires python3.10+"
@@ -23,8 +12,9 @@
     not sys.platform.startswith("linux"), reason="Test requires Linux"
 )
 
+shell = _get_shell_name()
 needs_bash = pytest.mark.skipif(
-    not shellingham or not shell or "bash" not in shell, reason="Test requires Bash"
+    shell is None or "bash" not in shell, reason="Test requires Bash"
 )
 
 requires_completion_permission = pytest.mark.skipif(

typer/_completion_classes.py

@@ -24,11 +24,6 @@
         split_arg_string as click_split_arg_string,
     )
 
-try:
-    import shellingham
-except ImportError:  # pragma: no cover
-    shellingham = None
-
 
 def _sanitize_help_text(text: str) -> str:
     """Sanitizes the help text by removing rich tags"""

typer/_completion_shared.py

@@ -3,14 +3,10 @@
 import subprocess
 from enum import Enum
 from pathlib import Path
-from typing import Optional, Tuple
+from typing import Optional, Tuple, Union
 
 import click
-
-try:
-    import shellingham
-except ImportError:  # pragma: no cover
-    shellingham = None
+from typer.core import HAS_SHELLINGHAM
 
 
 class Shells(str, Enum):
@@ -213,8 +209,8 @@ def install(
     if complete_var is None:
         complete_var = "_{}_COMPLETE".format(prog_name.replace("-", "_").upper())
     test_disable_detection = os.getenv("_TYPER_COMPLETE_TEST_DISABLE_SHELL_DETECTION")
-    if shell is None and shellingham is not None and not test_disable_detection:
-        shell, _ = shellingham.detect_shell()
+    if shell is None and not test_disable_detection:
+        shell = _get_shell_name()
     if shell == "bash":
         installed_path = install_bash(
             prog_name=prog_name, complete_var=complete_var, shell=shell
@@ -238,3 +234,25 @@ def install(
     else:
         click.echo(f"Shell {shell} is not supported.")
         raise click.exceptions.Exit(1)
+
+
+def _get_shell_name() -> Union[str, None]:
+    """Get the current shell name, if available.
+
+    The name will always be lowercase. If the shell cannot be detected, None is
+    returned.
+    """
+    name: Union[str, None]  # N.B. shellingham is untyped
+    if HAS_SHELLINGHAM:
+        import shellingham
+
+        try:
+            # N.B. detect_shell returns a tuple of (shell name, shell command).
+            # We only need the name.
+            name, _cmd = shellingham.detect_shell()  # noqa: TID251
+        except shellingham.ShellDetectionFailure:  # pragma: no cover
+            name = None
+    else:
+        name = None  # pragma: no cover
+
+    return name

typer/completion.py

@@ -5,24 +5,19 @@
 import click
 
 from ._completion_classes import completion_init
-from ._completion_shared import Shells, get_completion_script, install
+from ._completion_shared import Shells, _get_shell_name, get_completion_script, install
+from .core import HAS_SHELLINGHAM
 from .models import ParamMeta
 from .params import Option
 from .utils import get_params_from_function
 
-try:
-    import shellingham
-except ImportError:  # pragma: no cover
-    shellingham = None
-
-
 _click_patched = False
 
 
 def get_completion_inspect_parameters() -> Tuple[ParamMeta, ParamMeta]:
     completion_init()
     test_disable_detection = os.getenv("_TYPER_COMPLETE_TEST_DISABLE_SHELL_DETECTION")
-    if shellingham and not test_disable_detection:
+    if HAS_SHELLINGHAM and not test_disable_detection:
         parameters = get_params_from_function(_install_completion_placeholder_function)
     else:
         parameters = get_params_from_function(
@@ -54,8 +49,10 @@ def show_callback(ctx: click.Context, param: click.Parameter, value: Any) -> Any
     test_disable_detection = os.getenv("_TYPER_COMPLETE_TEST_DISABLE_SHELL_DETECTION")
     if isinstance(value, str):
         shell = value
-    elif shellingham and not test_disable_detection:
-        shell, _ = shellingham.detect_shell()
+    elif not test_disable_detection:
+        detected_shell = _get_shell_name()
+        if detected_shell is not None:
+            shell = detected_shell
     script_content = get_completion_script(
         prog_name=prog_name, complete_var=complete_var, shell=shell
     )

typer/core.py

@@ -32,6 +32,7 @@
 MarkupMode = Literal["markdown", "rich", None]
 
 HAS_RICH = importlib.util.find_spec("rich") is not None
+HAS_SHELLINGHAM = importlib.util.find_spec("shellingham") is not None
 
 if HAS_RICH:
     DEFAULT_MARKUP_MODE: MarkupMode = "rich"