Change sys.exit to raise ImportError (#2440)

The fix for #1688 in #1761 breaks help("modules") introspection and also leads
to unhappy results when inadvertently importing blackd from Python. Basically
the sys.exit(-1) causes the whole Python REPL to exit -- not great to suffice.

Commit history before merge:

* Change sys.exit to Raise.
* Add #2440 to changelog.
* Fix lint error from prettier
* Remove exception chain for more helpful user message.

Co-authored-by: Richard Si <63936253+ichard26@users.noreply.github.com>

diff --git a/CHANGES.md b/CHANGES.md
index 22ddc423e557e3f46031bd83a5cbb6b4bf2bf1d5..ed08ab3b9adb531e67d65c41ef77bb4d2fedb9b6 100644 (file)
--- a/CHANGES.md
+++ b/CHANGES.md
@@ -10,6 +10,10 @@
 - The failsafe for accidentally added backslashes in f-string expressions has been
   hardened to handle more edge cases during quote normalization (#2437)
 
+### _Blackd_
+
+- Replace sys.exit(-1) with raise ImportError (#2440)
+
 ### Integrations
 
 - The provided pre-commit hooks no longer specify `language_version` to avoid overriding

diff --git a/src/blackd/__init__.py b/src/blackd/__init__.py
index 3e2a7e7c30f3eb3ed18d51bd18b4322069b588c3..5fdec1522261b9775a90a2ee465d3304590ee8e6 100644 (file)
--- a/src/blackd/__init__.py
+++ b/src/blackd/__init__.py
@@ -1,6 +1,5 @@
 import asyncio
 import logging
-import sys
 from concurrent.futures import Executor, ProcessPoolExecutor
 from datetime import datetime
 from functools import partial
@@ -11,13 +10,11 @@ try:
     from aiohttp import web
     import aiohttp_cors
 except ImportError as ie:
-    print(
+    raise ImportError(
         f"aiohttp dependency is not installed: {ie}. "
         + "Please re-install black with the '[d]' extra install "
-        + "to obtain aiohttp_cors: `pip install black[d]`",
-        file=sys.stderr,
-    )
-    sys.exit(-1)
+        + "to obtain aiohttp_cors: `pip install black[d]`"
+    ) from None
 
 import black
 from black.concurrency import maybe_install_uvloop