From 3bd7fd2631a070f23ae35b311ab5f30c40db0fc6 Mon Sep 17 00:00:00 2001
From: snowdrop4 <82846066+snowdrop4@users.noreply.github.com>
Date: Mon, 25 Nov 2024 14:39:04 +0000
Subject: [PATCH 01/11] reduce false positives with single-letter names

---
 .../test/fixtures/pep8_naming/N811.py         |  5 ++++
 .../test/fixtures/pep8_naming/N814.py         |  5 ++++
 .../rules/camelcase_imported_as_constant.rs   |  5 ++++
 .../constant_imported_as_non_constant.rs      |  5 ++++
 ...les__pep8_naming__tests__N811_N811.py.snap | 28 +++++++++++--------
 ...les__pep8_naming__tests__N814_N814.py.snap | 28 +++++++++++--------
 6 files changed, 52 insertions(+), 24 deletions(-)

diff --git a/crates/ruff_linter/resources/test/fixtures/pep8_naming/N811.py b/crates/ruff_linter/resources/test/fixtures/pep8_naming/N811.py
index 0ef646edc9461..bf62e2de1840e 100644
--- a/crates/ruff_linter/resources/test/fixtures/pep8_naming/N811.py
+++ b/crates/ruff_linter/resources/test/fixtures/pep8_naming/N811.py
@@ -1,3 +1,8 @@
+# Error
 import mod.CONST as const
 from mod import CONSTANT as constant
 from mod import ANOTHER_CONSTANT as another_constant
+
+# Ok
+import django.db.models.Q as Query1
+from django.db.models import Q as Query2
diff --git a/crates/ruff_linter/resources/test/fixtures/pep8_naming/N814.py b/crates/ruff_linter/resources/test/fixtures/pep8_naming/N814.py
index 65a03383a5a28..82f0971c4ac7e 100644
--- a/crates/ruff_linter/resources/test/fixtures/pep8_naming/N814.py
+++ b/crates/ruff_linter/resources/test/fixtures/pep8_naming/N814.py
@@ -1,3 +1,8 @@
+# Error
 import mod.Camel as CAMEL
 from mod import CamelCase as CAMELCASE
 from mod import AnotherCamelCase as ANOTHER_CAMELCASE
+
+# Ok
+import mod.AppleFruit as A
+from mod import BananaFruit as B
diff --git a/crates/ruff_linter/src/rules/pep8_naming/rules/camelcase_imported_as_constant.rs b/crates/ruff_linter/src/rules/pep8_naming/rules/camelcase_imported_as_constant.rs
index f805bd2915e91..e41ac229c4044 100644
--- a/crates/ruff_linter/src/rules/pep8_naming/rules/camelcase_imported_as_constant.rs
+++ b/crates/ruff_linter/src/rules/pep8_naming/rules/camelcase_imported_as_constant.rs
@@ -53,6 +53,11 @@ pub(crate) fn camelcase_imported_as_constant(
     stmt: &Stmt,
     ignore_names: &IgnoreNames,
 ) -> Option<Diagnostic> {
+    // Single-character names are ambiguous. It could be a class or a constant.
+    if asname.chars().count() == 1 {
+        return None;
+    }
+
     if helpers::is_camelcase(name)
         && !str::is_cased_lowercase(asname)
         && str::is_cased_uppercase(asname)
diff --git a/crates/ruff_linter/src/rules/pep8_naming/rules/constant_imported_as_non_constant.rs b/crates/ruff_linter/src/rules/pep8_naming/rules/constant_imported_as_non_constant.rs
index 0f81043f60200..f71c5abd634f3 100644
--- a/crates/ruff_linter/src/rules/pep8_naming/rules/constant_imported_as_non_constant.rs
+++ b/crates/ruff_linter/src/rules/pep8_naming/rules/constant_imported_as_non_constant.rs
@@ -52,6 +52,11 @@ pub(crate) fn constant_imported_as_non_constant(
     stmt: &Stmt,
     ignore_names: &IgnoreNames,
 ) -> Option<Diagnostic> {
+    // Single-character names are ambiguous. It could be a class or a constant.
+    if name.chars().count() == 1 {
+        return None;
+    }
+
     if str::is_cased_uppercase(name) && !str::is_cased_uppercase(asname) {
         // Ignore any explicitly-allowed names.
         if ignore_names.matches(name) || ignore_names.matches(asname) {
diff --git a/crates/ruff_linter/src/rules/pep8_naming/snapshots/ruff_linter__rules__pep8_naming__tests__N811_N811.py.snap b/crates/ruff_linter/src/rules/pep8_naming/snapshots/ruff_linter__rules__pep8_naming__tests__N811_N811.py.snap
index fce6f320a792a..694ae6022ea9c 100644
--- a/crates/ruff_linter/src/rules/pep8_naming/snapshots/ruff_linter__rules__pep8_naming__tests__N811_N811.py.snap
+++ b/crates/ruff_linter/src/rules/pep8_naming/snapshots/ruff_linter__rules__pep8_naming__tests__N811_N811.py.snap
@@ -2,26 +2,30 @@
 source: crates/ruff_linter/src/rules/pep8_naming/mod.rs
 snapshot_kind: text
 ---
-N811.py:1:8: N811 Constant `CONST` imported as non-constant `const`
+N811.py:2:8: N811 Constant `CONST` imported as non-constant `const`
   |
-1 | import mod.CONST as const
+1 | # Error
+2 | import mod.CONST as const
   |        ^^^^^^^^^^^^^^^^^^ N811
-2 | from mod import CONSTANT as constant
-3 | from mod import ANOTHER_CONSTANT as another_constant
+3 | from mod import CONSTANT as constant
+4 | from mod import ANOTHER_CONSTANT as another_constant
   |
 
-N811.py:2:17: N811 Constant `CONSTANT` imported as non-constant `constant`
+N811.py:3:17: N811 Constant `CONSTANT` imported as non-constant `constant`
   |
-1 | import mod.CONST as const
-2 | from mod import CONSTANT as constant
+1 | # Error
+2 | import mod.CONST as const
+3 | from mod import CONSTANT as constant
   |                 ^^^^^^^^^^^^^^^^^^^^ N811
-3 | from mod import ANOTHER_CONSTANT as another_constant
+4 | from mod import ANOTHER_CONSTANT as another_constant
   |
 
-N811.py:3:17: N811 Constant `ANOTHER_CONSTANT` imported as non-constant `another_constant`
+N811.py:4:17: N811 Constant `ANOTHER_CONSTANT` imported as non-constant `another_constant`
   |
-1 | import mod.CONST as const
-2 | from mod import CONSTANT as constant
-3 | from mod import ANOTHER_CONSTANT as another_constant
+2 | import mod.CONST as const
+3 | from mod import CONSTANT as constant
+4 | from mod import ANOTHER_CONSTANT as another_constant
   |                 ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^ N811
+5 | 
+6 | # Ok
   |
diff --git a/crates/ruff_linter/src/rules/pep8_naming/snapshots/ruff_linter__rules__pep8_naming__tests__N814_N814.py.snap b/crates/ruff_linter/src/rules/pep8_naming/snapshots/ruff_linter__rules__pep8_naming__tests__N814_N814.py.snap
index d14b3e35951d6..37d05d2ca626b 100644
--- a/crates/ruff_linter/src/rules/pep8_naming/snapshots/ruff_linter__rules__pep8_naming__tests__N814_N814.py.snap
+++ b/crates/ruff_linter/src/rules/pep8_naming/snapshots/ruff_linter__rules__pep8_naming__tests__N814_N814.py.snap
@@ -2,26 +2,30 @@
 source: crates/ruff_linter/src/rules/pep8_naming/mod.rs
 snapshot_kind: text
 ---
-N814.py:1:8: N814 Camelcase `Camel` imported as constant `CAMEL`
+N814.py:2:8: N814 Camelcase `Camel` imported as constant `CAMEL`
   |
-1 | import mod.Camel as CAMEL
+1 | # Error
+2 | import mod.Camel as CAMEL
   |        ^^^^^^^^^^^^^^^^^^ N814
-2 | from mod import CamelCase as CAMELCASE
-3 | from mod import AnotherCamelCase as ANOTHER_CAMELCASE
+3 | from mod import CamelCase as CAMELCASE
+4 | from mod import AnotherCamelCase as ANOTHER_CAMELCASE
   |
 
-N814.py:2:17: N814 Camelcase `CamelCase` imported as constant `CAMELCASE`
+N814.py:3:17: N814 Camelcase `CamelCase` imported as constant `CAMELCASE`
   |
-1 | import mod.Camel as CAMEL
-2 | from mod import CamelCase as CAMELCASE
+1 | # Error
+2 | import mod.Camel as CAMEL
+3 | from mod import CamelCase as CAMELCASE
   |                 ^^^^^^^^^^^^^^^^^^^^^^ N814
-3 | from mod import AnotherCamelCase as ANOTHER_CAMELCASE
+4 | from mod import AnotherCamelCase as ANOTHER_CAMELCASE
   |
 
-N814.py:3:17: N814 Camelcase `AnotherCamelCase` imported as constant `ANOTHER_CAMELCASE`
+N814.py:4:17: N814 Camelcase `AnotherCamelCase` imported as constant `ANOTHER_CAMELCASE`
   |
-1 | import mod.Camel as CAMEL
-2 | from mod import CamelCase as CAMELCASE
-3 | from mod import AnotherCamelCase as ANOTHER_CAMELCASE
+2 | import mod.Camel as CAMEL
+3 | from mod import CamelCase as CAMELCASE
+4 | from mod import AnotherCamelCase as ANOTHER_CAMELCASE
   |                 ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^ N814
+5 | 
+6 | # Ok
   |

From 3da4c284f93770d299849f8dd3579865eb4b800e Mon Sep 17 00:00:00 2001
From: snowdrop4 <82846066+snowdrop4@users.noreply.github.com>
Date: Mon, 25 Nov 2024 23:06:15 +0000
Subject: [PATCH 02/11] don't rely on compiler optimisation

---
 .../rules/pep8_naming/rules/camelcase_imported_as_constant.rs | 4 +---
 .../pep8_naming/rules/constant_imported_as_non_constant.rs    | 4 +---
 2 files changed, 2 insertions(+), 6 deletions(-)

diff --git a/crates/ruff_linter/src/rules/pep8_naming/rules/camelcase_imported_as_constant.rs b/crates/ruff_linter/src/rules/pep8_naming/rules/camelcase_imported_as_constant.rs
index e41ac229c4044..64e17bca616d6 100644
--- a/crates/ruff_linter/src/rules/pep8_naming/rules/camelcase_imported_as_constant.rs
+++ b/crates/ruff_linter/src/rules/pep8_naming/rules/camelcase_imported_as_constant.rs
@@ -54,9 +54,7 @@ pub(crate) fn camelcase_imported_as_constant(
     ignore_names: &IgnoreNames,
 ) -> Option<Diagnostic> {
     // Single-character names are ambiguous. It could be a class or a constant.
-    if asname.chars().count() == 1 {
-        return None;
-    }
+    asname.chars().skip(1).next()?;
 
     if helpers::is_camelcase(name)
         && !str::is_cased_lowercase(asname)
diff --git a/crates/ruff_linter/src/rules/pep8_naming/rules/constant_imported_as_non_constant.rs b/crates/ruff_linter/src/rules/pep8_naming/rules/constant_imported_as_non_constant.rs
index f71c5abd634f3..132a873c857ba 100644
--- a/crates/ruff_linter/src/rules/pep8_naming/rules/constant_imported_as_non_constant.rs
+++ b/crates/ruff_linter/src/rules/pep8_naming/rules/constant_imported_as_non_constant.rs
@@ -53,9 +53,7 @@ pub(crate) fn constant_imported_as_non_constant(
     ignore_names: &IgnoreNames,
 ) -> Option<Diagnostic> {
     // Single-character names are ambiguous. It could be a class or a constant.
-    if name.chars().count() == 1 {
-        return None;
-    }
+    name.chars().skip(1).next()?;
 
     if str::is_cased_uppercase(name) && !str::is_cased_uppercase(asname) {
         // Ignore any explicitly-allowed names.

From b56d9334b12d36271e5d1af614e8ac18eba5ab55 Mon Sep 17 00:00:00 2001
From: snowdrop4 <82846066+snowdrop4@users.noreply.github.com>
Date: Mon, 25 Nov 2024 23:35:58 +0000
Subject: [PATCH 03/11] add one more test case

---
 .../test/fixtures/pep8_naming/N811.py         |  1 +
 ...les__pep8_naming__tests__N811_N811.py.snap | 40 ++++++++++++-------
 2 files changed, 26 insertions(+), 15 deletions(-)

diff --git a/crates/ruff_linter/resources/test/fixtures/pep8_naming/N811.py b/crates/ruff_linter/resources/test/fixtures/pep8_naming/N811.py
index bf62e2de1840e..e67e3afd9e8e0 100644
--- a/crates/ruff_linter/resources/test/fixtures/pep8_naming/N811.py
+++ b/crates/ruff_linter/resources/test/fixtures/pep8_naming/N811.py
@@ -1,4 +1,5 @@
 # Error
+import mod.CON as c
 import mod.CONST as const
 from mod import CONSTANT as constant
 from mod import ANOTHER_CONSTANT as another_constant
diff --git a/crates/ruff_linter/src/rules/pep8_naming/snapshots/ruff_linter__rules__pep8_naming__tests__N811_N811.py.snap b/crates/ruff_linter/src/rules/pep8_naming/snapshots/ruff_linter__rules__pep8_naming__tests__N811_N811.py.snap
index 694ae6022ea9c..0dcde0cfd21e2 100644
--- a/crates/ruff_linter/src/rules/pep8_naming/snapshots/ruff_linter__rules__pep8_naming__tests__N811_N811.py.snap
+++ b/crates/ruff_linter/src/rules/pep8_naming/snapshots/ruff_linter__rules__pep8_naming__tests__N811_N811.py.snap
@@ -2,30 +2,40 @@
 source: crates/ruff_linter/src/rules/pep8_naming/mod.rs
 snapshot_kind: text
 ---
-N811.py:2:8: N811 Constant `CONST` imported as non-constant `const`
+N811.py:2:8: N811 Constant `CON` imported as non-constant `c`
   |
 1 | # Error
-2 | import mod.CONST as const
-  |        ^^^^^^^^^^^^^^^^^^ N811
-3 | from mod import CONSTANT as constant
-4 | from mod import ANOTHER_CONSTANT as another_constant
+2 | import mod.CON as c
+  |        ^^^^^^^^^^^^ N811
+3 | import mod.CONST as const
+4 | from mod import CONSTANT as constant
   |
 
-N811.py:3:17: N811 Constant `CONSTANT` imported as non-constant `constant`
+N811.py:3:8: N811 Constant `CONST` imported as non-constant `const`
   |
 1 | # Error
-2 | import mod.CONST as const
-3 | from mod import CONSTANT as constant
+2 | import mod.CON as c
+3 | import mod.CONST as const
+  |        ^^^^^^^^^^^^^^^^^^ N811
+4 | from mod import CONSTANT as constant
+5 | from mod import ANOTHER_CONSTANT as another_constant
+  |
+
+N811.py:4:17: N811 Constant `CONSTANT` imported as non-constant `constant`
+  |
+2 | import mod.CON as c
+3 | import mod.CONST as const
+4 | from mod import CONSTANT as constant
   |                 ^^^^^^^^^^^^^^^^^^^^ N811
-4 | from mod import ANOTHER_CONSTANT as another_constant
+5 | from mod import ANOTHER_CONSTANT as another_constant
   |
 
-N811.py:4:17: N811 Constant `ANOTHER_CONSTANT` imported as non-constant `another_constant`
+N811.py:5:17: N811 Constant `ANOTHER_CONSTANT` imported as non-constant `another_constant`
   |
-2 | import mod.CONST as const
-3 | from mod import CONSTANT as constant
-4 | from mod import ANOTHER_CONSTANT as another_constant
+3 | import mod.CONST as const
+4 | from mod import CONSTANT as constant
+5 | from mod import ANOTHER_CONSTANT as another_constant
   |                 ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^ N811
-5 | 
-6 | # Ok
+6 | 
+7 | # Ok
   |

From 9396f38e60c0d4285d1ee8d6197ea087c6067e4a Mon Sep 17 00:00:00 2001
From: snowdrop4 <82846066+snowdrop4@users.noreply.github.com>
Date: Mon, 25 Nov 2024 23:36:09 +0000
Subject: [PATCH 04/11] add documentation about the ambiguity

---
 .../rules/camelcase_imported_as_constant.rs        | 14 ++++++++++++++
 .../rules/constant_imported_as_non_constant.rs     | 13 +++++++++++++
 2 files changed, 27 insertions(+)

diff --git a/crates/ruff_linter/src/rules/pep8_naming/rules/camelcase_imported_as_constant.rs b/crates/ruff_linter/src/rules/pep8_naming/rules/camelcase_imported_as_constant.rs
index 64e17bca616d6..9257ae632166f 100644
--- a/crates/ruff_linter/src/rules/pep8_naming/rules/camelcase_imported_as_constant.rs
+++ b/crates/ruff_linter/src/rules/pep8_naming/rules/camelcase_imported_as_constant.rs
@@ -30,6 +30,20 @@ use crate::rules::pep8_naming::settings::IgnoreNames;
 /// from example import MyClassName
 /// ```
 ///
+/// ## Note
+/// Identifiers consisting of a single uppercase character are ambigous under
+/// the rules of PEP8, which specifies PascalCase for classes and
+/// ALL_CAPS_SNAKE_CASE for constants. Without a second character, it is not
+/// possible to reliably guess whether the identifier is intended to be part
+/// of a PascalCase string for a class or an ALL_CAPS_SNAKE_CASE string for
+/// a constant, since both conventions will produce the same output when given
+/// a single input character. Therefore, this lint rule does not apply to cases
+/// where the alias for the imported identifier consists of a single uppercase
+/// character.
+///
+/// A common example of a single uppercase character being used for a class
+/// name can be found in Django's `django.db.models.Q` class.
+///
 /// [PEP 8]: https://peps.python.org/pep-0008/
 #[violation]
 pub struct CamelcaseImportedAsConstant {
diff --git a/crates/ruff_linter/src/rules/pep8_naming/rules/constant_imported_as_non_constant.rs b/crates/ruff_linter/src/rules/pep8_naming/rules/constant_imported_as_non_constant.rs
index 132a873c857ba..0bf33f6681e0a 100644
--- a/crates/ruff_linter/src/rules/pep8_naming/rules/constant_imported_as_non_constant.rs
+++ b/crates/ruff_linter/src/rules/pep8_naming/rules/constant_imported_as_non_constant.rs
@@ -29,6 +29,19 @@ use crate::rules::pep8_naming::settings::IgnoreNames;
 /// from example import CONSTANT_VALUE
 /// ```
 ///
+/// ## Note
+/// Identifiers consisting of a single uppercase character are ambigous under
+/// the rules of PEP8, which specifies PascalCase for classes and
+/// ALL_CAPS_SNAKE_CASE for constants. Without a second character, it is not
+/// possible to reliably guess whether the identifier is intended to be part
+/// of a PascalCase string for a class or an ALL_CAPS_SNAKE_CASE string for
+/// a constant, since both conventions will produce the same output when given
+/// a single input character. Therefore, this lint rule does not apply to cases
+/// where the imported identifier consists of a single uppercase character.
+///
+/// A common example of a single uppercase character being used for a class
+/// name can be found in Django's `django.db.models.Q` class.
+///
 /// [PEP 8]: https://peps.python.org/pep-0008/
 #[violation]
 pub struct ConstantImportedAsNonConstant {

From c811971d7a1e03a88ca624133dcf0a031310997f Mon Sep 17 00:00:00 2001
From: Micha Reiser <micha@reiser.io>
Date: Tue, 26 Nov 2024 09:08:39 +0100
Subject: [PATCH 05/11] Clippy and typo

---
 .../rules/pep8_naming/rules/camelcase_imported_as_constant.rs | 4 ++--
 .../pep8_naming/rules/constant_imported_as_non_constant.rs    | 4 ++--
 2 files changed, 4 insertions(+), 4 deletions(-)

diff --git a/crates/ruff_linter/src/rules/pep8_naming/rules/camelcase_imported_as_constant.rs b/crates/ruff_linter/src/rules/pep8_naming/rules/camelcase_imported_as_constant.rs
index 9257ae632166f..017dcd120481f 100644
--- a/crates/ruff_linter/src/rules/pep8_naming/rules/camelcase_imported_as_constant.rs
+++ b/crates/ruff_linter/src/rules/pep8_naming/rules/camelcase_imported_as_constant.rs
@@ -31,7 +31,7 @@ use crate::rules::pep8_naming::settings::IgnoreNames;
 /// ```
 ///
 /// ## Note
-/// Identifiers consisting of a single uppercase character are ambigous under
+/// Identifiers consisting of a single uppercase character are ambiguous under
 /// the rules of PEP8, which specifies PascalCase for classes and
 /// ALL_CAPS_SNAKE_CASE for constants. Without a second character, it is not
 /// possible to reliably guess whether the identifier is intended to be part
@@ -68,7 +68,7 @@ pub(crate) fn camelcase_imported_as_constant(
     ignore_names: &IgnoreNames,
 ) -> Option<Diagnostic> {
     // Single-character names are ambiguous. It could be a class or a constant.
-    asname.chars().skip(1).next()?;
+    asname.chars().nth(1)?;
 
     if helpers::is_camelcase(name)
         && !str::is_cased_lowercase(asname)
diff --git a/crates/ruff_linter/src/rules/pep8_naming/rules/constant_imported_as_non_constant.rs b/crates/ruff_linter/src/rules/pep8_naming/rules/constant_imported_as_non_constant.rs
index 0bf33f6681e0a..aeeb166ff6acf 100644
--- a/crates/ruff_linter/src/rules/pep8_naming/rules/constant_imported_as_non_constant.rs
+++ b/crates/ruff_linter/src/rules/pep8_naming/rules/constant_imported_as_non_constant.rs
@@ -30,7 +30,7 @@ use crate::rules::pep8_naming::settings::IgnoreNames;
 /// ```
 ///
 /// ## Note
-/// Identifiers consisting of a single uppercase character are ambigous under
+/// Identifiers consisting of a single uppercase character are ambiguous under
 /// the rules of PEP8, which specifies PascalCase for classes and
 /// ALL_CAPS_SNAKE_CASE for constants. Without a second character, it is not
 /// possible to reliably guess whether the identifier is intended to be part
@@ -66,7 +66,7 @@ pub(crate) fn constant_imported_as_non_constant(
     ignore_names: &IgnoreNames,
 ) -> Option<Diagnostic> {
     // Single-character names are ambiguous. It could be a class or a constant.
-    name.chars().skip(1).next()?;
+    name.chars().nth(1)?;
 
     if str::is_cased_uppercase(name) && !str::is_cased_uppercase(asname) {
         // Ignore any explicitly-allowed names.

From 1732d6b4e448ce76745b739a6206af846bfcd834 Mon Sep 17 00:00:00 2001
From: snowdrop4 <82846066+snowdrop4@users.noreply.github.com>
Date: Wed, 27 Nov 2024 13:57:44 +0000
Subject: [PATCH 06/11] remove comments from test files

---
 crates/ruff_linter/resources/test/fixtures/pep8_naming/N811.py | 2 --
 crates/ruff_linter/resources/test/fixtures/pep8_naming/N814.py | 2 --
 2 files changed, 4 deletions(-)

diff --git a/crates/ruff_linter/resources/test/fixtures/pep8_naming/N811.py b/crates/ruff_linter/resources/test/fixtures/pep8_naming/N811.py
index e67e3afd9e8e0..f71ae67dee81e 100644
--- a/crates/ruff_linter/resources/test/fixtures/pep8_naming/N811.py
+++ b/crates/ruff_linter/resources/test/fixtures/pep8_naming/N811.py
@@ -1,9 +1,7 @@
-# Error
 import mod.CON as c
 import mod.CONST as const
 from mod import CONSTANT as constant
 from mod import ANOTHER_CONSTANT as another_constant
 
-# Ok
 import django.db.models.Q as Query1
 from django.db.models import Q as Query2
diff --git a/crates/ruff_linter/resources/test/fixtures/pep8_naming/N814.py b/crates/ruff_linter/resources/test/fixtures/pep8_naming/N814.py
index 82f0971c4ac7e..0d47a4d0347fb 100644
--- a/crates/ruff_linter/resources/test/fixtures/pep8_naming/N814.py
+++ b/crates/ruff_linter/resources/test/fixtures/pep8_naming/N814.py
@@ -1,8 +1,6 @@
-# Error
 import mod.Camel as CAMEL
 from mod import CamelCase as CAMELCASE
 from mod import AnotherCamelCase as ANOTHER_CAMELCASE
 
-# Ok
 import mod.AppleFruit as A
 from mod import BananaFruit as B

From cfc70bb152cd289a55ff637061aabf4b82674e75 Mon Sep 17 00:00:00 2001
From: snowdrop4 <82846066+snowdrop4@users.noreply.github.com>
Date: Wed, 27 Nov 2024 13:58:46 +0000
Subject: [PATCH 07/11] change ordering of test file

---
 crates/ruff_linter/resources/test/fixtures/pep8_naming/N811.py | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/crates/ruff_linter/resources/test/fixtures/pep8_naming/N811.py b/crates/ruff_linter/resources/test/fixtures/pep8_naming/N811.py
index f71ae67dee81e..859edcc29b323 100644
--- a/crates/ruff_linter/resources/test/fixtures/pep8_naming/N811.py
+++ b/crates/ruff_linter/resources/test/fixtures/pep8_naming/N811.py
@@ -1,7 +1,7 @@
-import mod.CON as c
 import mod.CONST as const
 from mod import CONSTANT as constant
 from mod import ANOTHER_CONSTANT as another_constant
+import mod.CON as c
 
 import django.db.models.Q as Query1
 from django.db.models import Q as Query2

From 3de5771e656430be123b76e83cb0ce1d47929fd0 Mon Sep 17 00:00:00 2001
From: snowdrop4 <82846066+snowdrop4@users.noreply.github.com>
Date: Wed, 27 Nov 2024 14:03:36 +0000
Subject: [PATCH 08/11] docs

---
 .../rules/pep8_naming/rules/camelcase_imported_as_constant.rs | 4 ++--
 .../pep8_naming/rules/constant_imported_as_non_constant.rs    | 4 ++--
 2 files changed, 4 insertions(+), 4 deletions(-)

diff --git a/crates/ruff_linter/src/rules/pep8_naming/rules/camelcase_imported_as_constant.rs b/crates/ruff_linter/src/rules/pep8_naming/rules/camelcase_imported_as_constant.rs
index 017dcd120481f..49bda02d0ab8f 100644
--- a/crates/ruff_linter/src/rules/pep8_naming/rules/camelcase_imported_as_constant.rs
+++ b/crates/ruff_linter/src/rules/pep8_naming/rules/camelcase_imported_as_constant.rs
@@ -32,10 +32,10 @@ use crate::rules::pep8_naming::settings::IgnoreNames;
 ///
 /// ## Note
 /// Identifiers consisting of a single uppercase character are ambiguous under
-/// the rules of PEP8, which specifies PascalCase for classes and
+/// the rules of [PEP 8], which specifies CamelCase for classes and
 /// ALL_CAPS_SNAKE_CASE for constants. Without a second character, it is not
 /// possible to reliably guess whether the identifier is intended to be part
-/// of a PascalCase string for a class or an ALL_CAPS_SNAKE_CASE string for
+/// of a CamelCase string for a class or an ALL_CAPS_SNAKE_CASE string for
 /// a constant, since both conventions will produce the same output when given
 /// a single input character. Therefore, this lint rule does not apply to cases
 /// where the alias for the imported identifier consists of a single uppercase
diff --git a/crates/ruff_linter/src/rules/pep8_naming/rules/constant_imported_as_non_constant.rs b/crates/ruff_linter/src/rules/pep8_naming/rules/constant_imported_as_non_constant.rs
index aeeb166ff6acf..e2dae630d19ea 100644
--- a/crates/ruff_linter/src/rules/pep8_naming/rules/constant_imported_as_non_constant.rs
+++ b/crates/ruff_linter/src/rules/pep8_naming/rules/constant_imported_as_non_constant.rs
@@ -31,10 +31,10 @@ use crate::rules::pep8_naming::settings::IgnoreNames;
 ///
 /// ## Note
 /// Identifiers consisting of a single uppercase character are ambiguous under
-/// the rules of PEP8, which specifies PascalCase for classes and
+/// the rules of [PEP 8], which specifies CamelCase for classes and
 /// ALL_CAPS_SNAKE_CASE for constants. Without a second character, it is not
 /// possible to reliably guess whether the identifier is intended to be part
-/// of a PascalCase string for a class or an ALL_CAPS_SNAKE_CASE string for
+/// of a CamelCase string for a class or an ALL_CAPS_SNAKE_CASE string for
 /// a constant, since both conventions will produce the same output when given
 /// a single input character. Therefore, this lint rule does not apply to cases
 /// where the imported identifier consists of a single uppercase character.

From d261a0e04c4e39948519e7bccf3f911cee35e4c0 Mon Sep 17 00:00:00 2001
From: snowdrop4 <82846066+snowdrop4@users.noreply.github.com>
Date: Wed, 27 Nov 2024 14:05:34 +0000
Subject: [PATCH 09/11] new snaps

---
 ...les__pep8_naming__tests__N811_N811.py.snap | 50 +++++++++----------
 ...les__pep8_naming__tests__N814_N814.py.snap | 30 ++++++-----
 2 files changed, 38 insertions(+), 42 deletions(-)

diff --git a/crates/ruff_linter/src/rules/pep8_naming/snapshots/ruff_linter__rules__pep8_naming__tests__N811_N811.py.snap b/crates/ruff_linter/src/rules/pep8_naming/snapshots/ruff_linter__rules__pep8_naming__tests__N811_N811.py.snap
index 0dcde0cfd21e2..f4df43bc5b953 100644
--- a/crates/ruff_linter/src/rules/pep8_naming/snapshots/ruff_linter__rules__pep8_naming__tests__N811_N811.py.snap
+++ b/crates/ruff_linter/src/rules/pep8_naming/snapshots/ruff_linter__rules__pep8_naming__tests__N811_N811.py.snap
@@ -2,40 +2,38 @@
 source: crates/ruff_linter/src/rules/pep8_naming/mod.rs
 snapshot_kind: text
 ---
-N811.py:2:8: N811 Constant `CON` imported as non-constant `c`
+N811.py:1:8: N811 Constant `CONST` imported as non-constant `const`
   |
-1 | # Error
-2 | import mod.CON as c
-  |        ^^^^^^^^^^^^ N811
-3 | import mod.CONST as const
-4 | from mod import CONSTANT as constant
-  |
-
-N811.py:3:8: N811 Constant `CONST` imported as non-constant `const`
-  |
-1 | # Error
-2 | import mod.CON as c
-3 | import mod.CONST as const
+1 | import mod.CONST as const
   |        ^^^^^^^^^^^^^^^^^^ N811
-4 | from mod import CONSTANT as constant
-5 | from mod import ANOTHER_CONSTANT as another_constant
+2 | from mod import CONSTANT as constant
+3 | from mod import ANOTHER_CONSTANT as another_constant
   |
 
-N811.py:4:17: N811 Constant `CONSTANT` imported as non-constant `constant`
+N811.py:2:17: N811 Constant `CONSTANT` imported as non-constant `constant`
   |
-2 | import mod.CON as c
-3 | import mod.CONST as const
-4 | from mod import CONSTANT as constant
+1 | import mod.CONST as const
+2 | from mod import CONSTANT as constant
   |                 ^^^^^^^^^^^^^^^^^^^^ N811
-5 | from mod import ANOTHER_CONSTANT as another_constant
+3 | from mod import ANOTHER_CONSTANT as another_constant
+4 | import mod.CON as c
   |
 
-N811.py:5:17: N811 Constant `ANOTHER_CONSTANT` imported as non-constant `another_constant`
+N811.py:3:17: N811 Constant `ANOTHER_CONSTANT` imported as non-constant `another_constant`
   |
-3 | import mod.CONST as const
-4 | from mod import CONSTANT as constant
-5 | from mod import ANOTHER_CONSTANT as another_constant
+1 | import mod.CONST as const
+2 | from mod import CONSTANT as constant
+3 | from mod import ANOTHER_CONSTANT as another_constant
   |                 ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^ N811
-6 | 
-7 | # Ok
+4 | import mod.CON as c
+  |
+
+N811.py:4:8: N811 Constant `CON` imported as non-constant `c`
+  |
+2 | from mod import CONSTANT as constant
+3 | from mod import ANOTHER_CONSTANT as another_constant
+4 | import mod.CON as c
+  |        ^^^^^^^^^^^^ N811
+5 | 
+6 | import django.db.models.Q as Query1
   |
diff --git a/crates/ruff_linter/src/rules/pep8_naming/snapshots/ruff_linter__rules__pep8_naming__tests__N814_N814.py.snap b/crates/ruff_linter/src/rules/pep8_naming/snapshots/ruff_linter__rules__pep8_naming__tests__N814_N814.py.snap
index 37d05d2ca626b..df0d4f983f684 100644
--- a/crates/ruff_linter/src/rules/pep8_naming/snapshots/ruff_linter__rules__pep8_naming__tests__N814_N814.py.snap
+++ b/crates/ruff_linter/src/rules/pep8_naming/snapshots/ruff_linter__rules__pep8_naming__tests__N814_N814.py.snap
@@ -2,30 +2,28 @@
 source: crates/ruff_linter/src/rules/pep8_naming/mod.rs
 snapshot_kind: text
 ---
-N814.py:2:8: N814 Camelcase `Camel` imported as constant `CAMEL`
+N814.py:1:8: N814 Camelcase `Camel` imported as constant `CAMEL`
   |
-1 | # Error
-2 | import mod.Camel as CAMEL
+1 | import mod.Camel as CAMEL
   |        ^^^^^^^^^^^^^^^^^^ N814
-3 | from mod import CamelCase as CAMELCASE
-4 | from mod import AnotherCamelCase as ANOTHER_CAMELCASE
+2 | from mod import CamelCase as CAMELCASE
+3 | from mod import AnotherCamelCase as ANOTHER_CAMELCASE
   |
 
-N814.py:3:17: N814 Camelcase `CamelCase` imported as constant `CAMELCASE`
+N814.py:2:17: N814 Camelcase `CamelCase` imported as constant `CAMELCASE`
   |
-1 | # Error
-2 | import mod.Camel as CAMEL
-3 | from mod import CamelCase as CAMELCASE
+1 | import mod.Camel as CAMEL
+2 | from mod import CamelCase as CAMELCASE
   |                 ^^^^^^^^^^^^^^^^^^^^^^ N814
-4 | from mod import AnotherCamelCase as ANOTHER_CAMELCASE
+3 | from mod import AnotherCamelCase as ANOTHER_CAMELCASE
   |
 
-N814.py:4:17: N814 Camelcase `AnotherCamelCase` imported as constant `ANOTHER_CAMELCASE`
+N814.py:3:17: N814 Camelcase `AnotherCamelCase` imported as constant `ANOTHER_CAMELCASE`
   |
-2 | import mod.Camel as CAMEL
-3 | from mod import CamelCase as CAMELCASE
-4 | from mod import AnotherCamelCase as ANOTHER_CAMELCASE
+1 | import mod.Camel as CAMEL
+2 | from mod import CamelCase as CAMELCASE
+3 | from mod import AnotherCamelCase as ANOTHER_CAMELCASE
   |                 ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^ N814
-5 | 
-6 | # Ok
+4 | 
+5 | import mod.AppleFruit as A
   |

From e9af7fac2a389fa43f12e220499a19784330210b Mon Sep 17 00:00:00 2001
From: snowdrop4 <82846066+snowdrop4@users.noreply.github.com>
Date: Wed, 27 Nov 2024 14:13:36 +0000
Subject: [PATCH 10/11] backticks in docs to appease clippy

---
 .../pep8_naming/rules/camelcase_imported_as_constant.rs     | 6 +++---
 .../pep8_naming/rules/constant_imported_as_non_constant.rs  | 6 +++---
 2 files changed, 6 insertions(+), 6 deletions(-)

diff --git a/crates/ruff_linter/src/rules/pep8_naming/rules/camelcase_imported_as_constant.rs b/crates/ruff_linter/src/rules/pep8_naming/rules/camelcase_imported_as_constant.rs
index 49bda02d0ab8f..e4fdce67bc931 100644
--- a/crates/ruff_linter/src/rules/pep8_naming/rules/camelcase_imported_as_constant.rs
+++ b/crates/ruff_linter/src/rules/pep8_naming/rules/camelcase_imported_as_constant.rs
@@ -32,10 +32,10 @@ use crate::rules::pep8_naming::settings::IgnoreNames;
 ///
 /// ## Note
 /// Identifiers consisting of a single uppercase character are ambiguous under
-/// the rules of [PEP 8], which specifies CamelCase for classes and
-/// ALL_CAPS_SNAKE_CASE for constants. Without a second character, it is not
+/// the rules of [PEP 8], which specifies `CamelCase` for classes and
+/// `ALL_CAPS_SNAKE_CASE` for constants. Without a second character, it is not
 /// possible to reliably guess whether the identifier is intended to be part
-/// of a CamelCase string for a class or an ALL_CAPS_SNAKE_CASE string for
+/// of a `CamelCase` string for a class or an `ALL_CAPS_SNAKE_CASE` string for
 /// a constant, since both conventions will produce the same output when given
 /// a single input character. Therefore, this lint rule does not apply to cases
 /// where the alias for the imported identifier consists of a single uppercase
diff --git a/crates/ruff_linter/src/rules/pep8_naming/rules/constant_imported_as_non_constant.rs b/crates/ruff_linter/src/rules/pep8_naming/rules/constant_imported_as_non_constant.rs
index e2dae630d19ea..92e6b135a6596 100644
--- a/crates/ruff_linter/src/rules/pep8_naming/rules/constant_imported_as_non_constant.rs
+++ b/crates/ruff_linter/src/rules/pep8_naming/rules/constant_imported_as_non_constant.rs
@@ -31,10 +31,10 @@ use crate::rules::pep8_naming::settings::IgnoreNames;
 ///
 /// ## Note
 /// Identifiers consisting of a single uppercase character are ambiguous under
-/// the rules of [PEP 8], which specifies CamelCase for classes and
-/// ALL_CAPS_SNAKE_CASE for constants. Without a second character, it is not
+/// the rules of [PEP 8], which specifies `CamelCase` for classes and
+/// `ALL_CAPS_SNAKE_CASE` for constants. Without a second character, it is not
 /// possible to reliably guess whether the identifier is intended to be part
-/// of a CamelCase string for a class or an ALL_CAPS_SNAKE_CASE string for
+/// of a `CamelCase` string for a class or an `ALL_CAPS_SNAKE_CASE` string for
 /// a constant, since both conventions will produce the same output when given
 /// a single input character. Therefore, this lint rule does not apply to cases
 /// where the imported identifier consists of a single uppercase character.

From 7ae363ccd236e9cfff26bd514a60ccf728e02632 Mon Sep 17 00:00:00 2001
From: Alex Waygood <alex.waygood@gmail.com>
Date: Wed, 27 Nov 2024 14:20:12 +0000
Subject: [PATCH 11/11] Ensure N811 flags single-character constants imported
 as lowercase

---
 .../resources/test/fixtures/pep8_naming/N811.py   |  2 ++
 .../resources/test/fixtures/pep8_naming/N814.py   |  1 +
 .../rules/constant_imported_as_non_constant.rs    | 13 ++++++++-----
 ...__rules__pep8_naming__tests__N811_N811.py.snap | 15 ++++++++++++---
 ...__rules__pep8_naming__tests__N814_N814.py.snap |  3 +--
 5 files changed, 24 insertions(+), 10 deletions(-)

diff --git a/crates/ruff_linter/resources/test/fixtures/pep8_naming/N811.py b/crates/ruff_linter/resources/test/fixtures/pep8_naming/N811.py
index 859edcc29b323..c18b8f992d859 100644
--- a/crates/ruff_linter/resources/test/fixtures/pep8_naming/N811.py
+++ b/crates/ruff_linter/resources/test/fixtures/pep8_naming/N811.py
@@ -2,6 +2,8 @@
 from mod import CONSTANT as constant
 from mod import ANOTHER_CONSTANT as another_constant
 import mod.CON as c
+from mod import C as c
 
+# These are all OK:
 import django.db.models.Q as Query1
 from django.db.models import Q as Query2
diff --git a/crates/ruff_linter/resources/test/fixtures/pep8_naming/N814.py b/crates/ruff_linter/resources/test/fixtures/pep8_naming/N814.py
index 0d47a4d0347fb..4a6809043000c 100644
--- a/crates/ruff_linter/resources/test/fixtures/pep8_naming/N814.py
+++ b/crates/ruff_linter/resources/test/fixtures/pep8_naming/N814.py
@@ -2,5 +2,6 @@
 from mod import CamelCase as CAMELCASE
 from mod import AnotherCamelCase as ANOTHER_CAMELCASE
 
+# These are all OK:
 import mod.AppleFruit as A
 from mod import BananaFruit as B
diff --git a/crates/ruff_linter/src/rules/pep8_naming/rules/constant_imported_as_non_constant.rs b/crates/ruff_linter/src/rules/pep8_naming/rules/constant_imported_as_non_constant.rs
index 92e6b135a6596..ef6197aa08f8a 100644
--- a/crates/ruff_linter/src/rules/pep8_naming/rules/constant_imported_as_non_constant.rs
+++ b/crates/ruff_linter/src/rules/pep8_naming/rules/constant_imported_as_non_constant.rs
@@ -4,7 +4,7 @@ use ruff_python_ast::{Alias, Stmt};
 use ruff_python_stdlib::str;
 use ruff_text_size::Ranged;
 
-use crate::rules::pep8_naming::settings::IgnoreNames;
+use crate::rules::pep8_naming::{helpers, settings::IgnoreNames};
 
 /// ## What it does
 /// Checks for constant imports that are aliased to non-constant-style
@@ -65,10 +65,13 @@ pub(crate) fn constant_imported_as_non_constant(
     stmt: &Stmt,
     ignore_names: &IgnoreNames,
 ) -> Option<Diagnostic> {
-    // Single-character names are ambiguous. It could be a class or a constant.
-    name.chars().nth(1)?;
-
-    if str::is_cased_uppercase(name) && !str::is_cased_uppercase(asname) {
+    if str::is_cased_uppercase(name)
+        && !(str::is_cased_uppercase(asname)
+            // Single-character names are ambiguous.
+            // It could be a class or a constant, so allow it to be imported
+            // as `SCREAMING_SNAKE_CASE` *or* `CamelCase`.
+            || (name.chars().nth(1).is_none() && helpers::is_camelcase(asname)))
+    {
         // Ignore any explicitly-allowed names.
         if ignore_names.matches(name) || ignore_names.matches(asname) {
             return None;
diff --git a/crates/ruff_linter/src/rules/pep8_naming/snapshots/ruff_linter__rules__pep8_naming__tests__N811_N811.py.snap b/crates/ruff_linter/src/rules/pep8_naming/snapshots/ruff_linter__rules__pep8_naming__tests__N811_N811.py.snap
index f4df43bc5b953..680195dbffe53 100644
--- a/crates/ruff_linter/src/rules/pep8_naming/snapshots/ruff_linter__rules__pep8_naming__tests__N811_N811.py.snap
+++ b/crates/ruff_linter/src/rules/pep8_naming/snapshots/ruff_linter__rules__pep8_naming__tests__N811_N811.py.snap
@@ -1,6 +1,5 @@
 ---
 source: crates/ruff_linter/src/rules/pep8_naming/mod.rs
-snapshot_kind: text
 ---
 N811.py:1:8: N811 Constant `CONST` imported as non-constant `const`
   |
@@ -26,6 +25,7 @@ N811.py:3:17: N811 Constant `ANOTHER_CONSTANT` imported as non-constant `another
 3 | from mod import ANOTHER_CONSTANT as another_constant
   |                 ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^ N811
 4 | import mod.CON as c
+5 | from mod import C as c
   |
 
 N811.py:4:8: N811 Constant `CON` imported as non-constant `c`
@@ -34,6 +34,15 @@ N811.py:4:8: N811 Constant `CON` imported as non-constant `c`
 3 | from mod import ANOTHER_CONSTANT as another_constant
 4 | import mod.CON as c
   |        ^^^^^^^^^^^^ N811
-5 | 
-6 | import django.db.models.Q as Query1
+5 | from mod import C as c
+  |
+
+N811.py:5:17: N811 Constant `C` imported as non-constant `c`
+  |
+3 | from mod import ANOTHER_CONSTANT as another_constant
+4 | import mod.CON as c
+5 | from mod import C as c
+  |                 ^^^^^^ N811
+6 | 
+7 | # These are all OK:
   |
diff --git a/crates/ruff_linter/src/rules/pep8_naming/snapshots/ruff_linter__rules__pep8_naming__tests__N814_N814.py.snap b/crates/ruff_linter/src/rules/pep8_naming/snapshots/ruff_linter__rules__pep8_naming__tests__N814_N814.py.snap
index df0d4f983f684..57da8ddfaeed8 100644
--- a/crates/ruff_linter/src/rules/pep8_naming/snapshots/ruff_linter__rules__pep8_naming__tests__N814_N814.py.snap
+++ b/crates/ruff_linter/src/rules/pep8_naming/snapshots/ruff_linter__rules__pep8_naming__tests__N814_N814.py.snap
@@ -1,6 +1,5 @@
 ---
 source: crates/ruff_linter/src/rules/pep8_naming/mod.rs
-snapshot_kind: text
 ---
 N814.py:1:8: N814 Camelcase `Camel` imported as constant `CAMEL`
   |
@@ -25,5 +24,5 @@ N814.py:3:17: N814 Camelcase `AnotherCamelCase` imported as constant `ANOTHER_CA
 3 | from mod import AnotherCamelCase as ANOTHER_CAMELCASE
   |                 ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^ N814
 4 | 
-5 | import mod.AppleFruit as A
+5 | # These are all OK:
   |