Revert to treating exclude in .ini as single string

docs/source/config_file.rst

@@ -197,18 +197,28 @@ section of the command line docs.
 
 .. confval:: exclude
 
- :type: newline separated list of regular expressions
+ :type: regular expression
 
- A newline list of regular expression that matches file names, directory names and paths
+ A regular expression that matches file names, directory names and paths
  which mypy should ignore while recursively discovering files to check.
  Use forward slashes on all platforms.
 
  .. code-block:: ini
 
  [mypy]
- exclude =
- ^file1\.py$
- ^file2\.py$
+ exclude = (?x)(
+ ^one\.py$ # files named "one.py"
+ | two\.pyi$ # or files ending with "two.pyi"
+ | ^three\. # or files starting with "three."
+ )
+
+ Crafting a single regular expression that excludes multiple files while remaining
+ human-readable can be a challenge. The above example demonstrates one approach.
+ ``(?x)`` enables the ``VERBOSE`` flag for the subsequent regular expression, which
+ `ignores most whitespace and supports comments`__. The above is equivalent to:
+ ``(^one\.py$|two\.pyi$|^three\.)``.
+
+ .. __: https://docs.python.org/3/library/re.html#re.X
 
  For more details, see :option:`--exclude <mypy --exclude>`.
 

mypy/config_parser.py

@@ -126,7 +126,7 @@ def check_follow_imports(choice: str) -> str:
  'cache_dir': expand_path,
  'python_executable': expand_path,
  'strict': bool,
- 'exclude': lambda s: [p.strip() for p in s.split('\n') if p.strip()],
+ 'exclude': lambda s: [s.strip()],
 }
 
 # Reuse the ini_config_types and overwrite the diff

test-data/unit/cmdline.test

@@ -1354,9 +1354,10 @@ b/bpkg.py:1: error: "int" not callable
 # cmd: mypy .
 [file mypy.ini]
 \[mypy]
-exclude =
- abc
- b
+exclude = (?x)(
+ ^abc/
+ |^b/
+ )
 [file abc/apkg.py]
 1()
 [file b/bpkg.py]