From 1d010d093ae2b141855e00119136b50bcadc2692 Mon Sep 17 00:00:00 2001
From: Matt Bogosian <matt@bogosian.net>
Date: Fri, 31 Dec 2021 19:45:14 -0600
Subject: [PATCH 1/3] Revert to treating exclude in .ini as single string

Partially reverts #11329 (with respect to `.ini` documentation).
Modifies existing unit tests.

Fixes #11830.
---
 docs/source/config_file.rst | 9 +++++----
 mypy/config_parser.py       | 2 +-
 test-data/unit/cmdline.test | 7 ++++---
 3 files changed, 10 insertions(+), 8 deletions(-)

diff --git a/docs/source/config_file.rst b/docs/source/config_file.rst
index c34f23d9e169..28548398cff9 100644
--- a/docs/source/config_file.rst
+++ b/docs/source/config_file.rst
@@ -197,18 +197,19 @@ section of the command line docs.
 
 .. confval:: exclude
 
-    :type: newline separated list of regular expressions
+    :type: regular expressions
 
-    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 =
+      exclude = (?x)(
           ^file1\.py$
-          ^file2\.py$
+          |^file2\.py$
+        )
 
     For more details, see :option:`--exclude <mypy --exclude>`.
 
diff --git a/mypy/config_parser.py b/mypy/config_parser.py
index 24e61df0441c..f637e7d0ad14 100644
--- a/mypy/config_parser.py
+++ b/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
diff --git a/test-data/unit/cmdline.test b/test-data/unit/cmdline.test
index 6fa4d210a826..690b0cc06709 100644
--- a/test-data/unit/cmdline.test
+++ b/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]

From c197a70dd2c10c8c75ba96d38a3e666be19b9ab2 Mon Sep 17 00:00:00 2001
From: Matt Bogosian <matt@bogosian.net>
Date: Sat, 1 Jan 2022 18:26:23 -0600
Subject: [PATCH 2/3] Update docs/source/config_file.rst

Co-authored-by: Matthew W <matthew@willcockson.family>
---
 docs/source/config_file.rst | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/docs/source/config_file.rst b/docs/source/config_file.rst
index 28548398cff9..9a278b23327d 100644
--- a/docs/source/config_file.rst
+++ b/docs/source/config_file.rst
@@ -197,7 +197,7 @@ section of the command line docs.
 
 .. confval:: exclude
 
-    :type: regular expressions
+    :type: regular expression
 
     A regular expression that matches file names, directory names and paths
     which mypy should ignore while recursively discovering files to check.

From 6cb514d962f6e52443afb46ee7ac2fb7d4d2c177 Mon Sep 17 00:00:00 2001
From: Matt Bogosian <matt@bogosian.net>
Date: Sat, 1 Jan 2022 19:06:18 -0600
Subject: [PATCH 3/3] Proposal to address reviewer feedback

Add explanation of regex in ``.ini`` example per @mawillcockson's suggestion.
---
 docs/source/config_file.rst | 13 +++++++++++--
 1 file changed, 11 insertions(+), 2 deletions(-)

diff --git a/docs/source/config_file.rst b/docs/source/config_file.rst
index 9a278b23327d..889d6ebfa1b4 100644
--- a/docs/source/config_file.rst
+++ b/docs/source/config_file.rst
@@ -207,10 +207,19 @@ section of the command line docs.
 
       [mypy]
       exclude = (?x)(
-          ^file1\.py$
-          |^file2\.py$
+          ^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>`.
 
     This option may only be set in the global section (``[mypy]``).