Implement D200 (OneLinerDocstring) (#397)

resources/test/fixtures/D200.py

@@ -0,0 +1,25 @@
+def f():
+    """
+    Fail.
+    """
+
+
+def f():
+    """Fail.
+    """
+
+
+def f():
+    """
+    Fail."""
+
+
+def f():
+    """Pass."""
+
+
+def f():
+    """Pass.
+
+    More content here.
+    """

src/check_ast.rs

@@ -1890,6 +1890,9 @@ impl<'a> Checker<'a> {
 
     fn check_docstrings(&mut self) {
         while let Some(docstring) = self.docstrings.pop() {
+            if self.settings.enabled.contains(&CheckCode::D200) {
+                docstrings::one_liner(self, &docstring);
+            }
             if self.settings.enabled.contains(&CheckCode::D400) {
                 docstrings::ends_with_period(self, &docstring);
             }

src/checks.rs

@@ -151,6 +151,7 @@ pub enum CheckCode {
     U007,
     U008,
     // pydocstyle
+    D200,
     D400,
     D419,
     // Meta
@@ -250,6 +251,7 @@ pub enum CheckKind {
     UsePEP604Annotation,
     SuperCallWithParameters,
     // pydocstyle
+    OneLinerDocstring,
     EmptyDocstring,
     DocstringEndsInNonPeriod,
     // Meta
@@ -361,6 +363,7 @@ impl CheckCode {
             CheckCode::U007 => CheckKind::UsePEP604Annotation,
             CheckCode::U008 => CheckKind::SuperCallWithParameters,
             // pydocstyle
+            CheckCode::D200 => CheckKind::OneLinerDocstring,
             CheckCode::D400 => CheckKind::DocstringEndsInNonPeriod,
             CheckCode::D419 => CheckKind::EmptyDocstring,
             // Meta
@@ -451,6 +454,7 @@ impl CheckKind {
             CheckKind::UselessObjectInheritance(_) => &CheckCode::U004,
             CheckKind::SuperCallWithParameters => &CheckCode::U008,
             // pydocstyle
+            CheckKind::OneLinerDocstring => &CheckCode::D200,
             CheckKind::DocstringEndsInNonPeriod => &CheckCode::D400,
             CheckKind::EmptyDocstring => &CheckCode::D419,
             // Meta
@@ -697,6 +701,7 @@ impl CheckKind {
                 "Use `super()` instead of `super(__class__, self)`".to_string()
             }
             // pydocstyle
+            CheckKind::OneLinerDocstring => "One-line docstring should fit on one line".to_string(),
             CheckKind::DocstringEndsInNonPeriod => {
                 "First line should end with a period".to_string()
             }

src/docstrings.rs

@@ -61,6 +61,33 @@ pub fn extract<'a, 'b>(
     None
 }
 
+pub fn one_liner(checker: &mut Checker, docstring: &Docstring) {
+    if let ExprKind::Constant {
+        value: Constant::Str(string),
+        ..
+    } = &docstring.expr.node
+    {
+        let mut line_count = 0;
+        let mut non_empty_line_count = 0;
+        for line in string.lines() {
+            line_count += 1;
+            if !line.trim().is_empty() {
+                non_empty_line_count += 1;
+            }
+            if non_empty_line_count > 1 {
+                return;
+            }
+        }
+
+        if non_empty_line_count == 1 && line_count > 1 {
+            checker.add_check(Check::new(
+                CheckKind::OneLinerDocstring,
+                Range::from_located(docstring.expr),
+            ));
+        }
+    }
+}
+
 pub fn not_empty(checker: &mut Checker, docstring: &Docstring) {
     if let ExprKind::Constant {
         value: Constant::Str(string),

src/linter.rs

@@ -978,6 +978,18 @@ mod tests {
         Ok(())
     }
 
+    #[test]
+    fn d200() -> Result<()> {
+        let mut checks = check_path(
+            Path::new("./resources/test/fixtures/D200.py"),
+            &settings::Settings::for_rule(CheckCode::D200),
+            &fixer::Mode::Generate,
+        )?;
+        checks.sort_by_key(|check| check.location);
+        insta::assert_yaml_snapshot!(checks);
+        Ok(())
+    }
+
     #[test]
     fn d400() -> Result<()> {
         let mut checks = check_path(

src/snapshots/ruff__linter__tests__d200.snap

@@ -0,0 +1,29 @@
+---
+source: src/linter.rs
+expression: checks
+---
+- kind: OneLinerDocstring
+  location:
+    row: 2
+    column: 6
+  end_location:
+    row: 4
+    column: 8
+  fix: ~
+- kind: OneLinerDocstring
+  location:
+    row: 8
+    column: 6
+  end_location:
+    row: 9
+    column: 8
+  fix: ~
+- kind: OneLinerDocstring
+  location:
+    row: 13
+    column: 6
+  end_location:
+    row: 14
+    column: 13
+  fix: ~
+

src/snapshots/ruff__linter__tests__d400.snap

@@ -2,7 +2,7 @@
 source: src/linter.rs
 expression: checks
 ---
-- kind: DocstringEndsInPeriod
+- kind: DocstringEndsInNonPeriod
   location:
     row: 9
     column: 6
@@ -10,7 +10,7 @@ expression: checks
     row: 12
     column: 8
   fix: ~
-- kind: DocstringEndsInPeriod
+- kind: DocstringEndsInNonPeriod
   location:
     row: 16
     column: 6

src/snapshots/ruff__linter__tests__d400.snap.new

@@ -1,22 +0,0 @@
----
-source: src/linter.rs
-assertion_line: 989
-expression: checks
----
-- kind: DocstringEndsInNonPeriod
-  location:
-    row: 9
-    column: 6
-  end_location:
-    row: 12
-    column: 8
-  fix: ~
-- kind: DocstringEndsInNonPeriod
-  location:
-    row: 16
-    column: 6
-  end_location:
-    row: 19
-    column: 8
-  fix: ~
-