Normalize implicit concatenated f-string quotes per part (#13539)

crates/ruff_python_formatter/generate.py

@@ -33,14 +33,15 @@ node_lines = (
 nodes = []
 for node_line in node_lines:
     node = node_line.split("(")[1].split(")")[0].split("::")[-1].split("<")[0]
-    # `FString` and `StringLiteral` has a custom implementation while the formatting for
+    # `FString` has a custom implementation while the formatting for
-    # `FStringLiteralElement` and `FStringExpressionElement` are handled by the `FString`
+    # `FStringLiteralElement`, `FStringFormatSpec` and `FStringExpressionElement` are handled by the `FString`
     # implementation.
     if node in (
         "FString",
-        "StringLiteral",
         "FStringLiteralElement",
         "FStringExpressionElement",
+        "FStringFormatSpec",
+        "Identifier",
     ):
         continue
     nodes.append(node)

crates/ruff_python_formatter/resources/test/fixtures/ruff/expression/fstring.py

@@ -307,3 +307,11 @@ hello {
           ]
       } --------
 """
+
+
+# Implicit concatenated f-string containing quotes
+_ = (
+    'This string should change its quotes to double quotes'
+    f'This string uses double quotes in an expression {"woah"}'
+    f'This f-string does not use any quotes.'
+)

crates/ruff_python_formatter/src/expression/expr_string_literal.rs

@@ -4,37 +4,17 @@ use ruff_python_ast::{AnyNodeRef, ExprStringLiteral};
 use crate::expression::parentheses::{
     in_parentheses_only_group, NeedsParentheses, OptionalParentheses,
 };
-use crate::other::string_literal::{FormatStringLiteral, StringLiteralKind};
+use crate::other::string_literal::StringLiteralKind;
 use crate::prelude::*;
 use crate::string::{AnyString, FormatImplicitConcatenatedString};
 
 #[derive(Default)]
 pub struct FormatExprStringLiteral {
-    kind: ExprStringLiteralKind,
+    kind: StringLiteralKind,
-}
-
-#[derive(Default, Copy, Clone, Debug)]
-pub enum ExprStringLiteralKind {
-    #[default]
-    String,
-    Docstring,
-}
-
-impl ExprStringLiteralKind {
-    const fn string_literal_kind(self) -> StringLiteralKind {
-        match self {
-            ExprStringLiteralKind::String => StringLiteralKind::String,
-            ExprStringLiteralKind::Docstring => StringLiteralKind::Docstring,
-        }
-    }
-
-    const fn is_docstring(self) -> bool {
-        matches!(self, ExprStringLiteralKind::Docstring)
-    }
 }
 
 impl FormatRuleWithOptions<ExprStringLiteral, PyFormatContext<'_>> for FormatExprStringLiteral {
-    type Options = ExprStringLiteralKind;
+    type Options = StringLiteralKind;
 
     fn with_options(mut self, options: Self::Options) -> Self {
         self.kind = options;
@@ -47,9 +27,7 @@ impl FormatNodeRule<ExprStringLiteral> for FormatExprStringLiteral {
         let ExprStringLiteral { value, .. } = item;
 
         match value.as_slice() {
-            [string_literal] => {
+            [string_literal] => string_literal.format().with_options(self.kind).fmt(f),
-                FormatStringLiteral::new(string_literal, self.kind.string_literal_kind()).fmt(f)
-            }
             _ => {
                 // This is just a sanity check because [`DocstringStmt::try_from_statement`]
                 // ensures that the docstring is a *single* string literal.

crates/ruff_python_formatter/src/generated.rs

@@ -2935,6 +2935,42 @@ impl<'ast> IntoFormat<PyFormatContext<'ast>> for ast::TypeParamParamSpec {
     }
 }
 
+impl FormatRule<ast::StringLiteral, PyFormatContext<'_>>
+    for crate::other::string_literal::FormatStringLiteral
+{
+    #[inline]
+    fn fmt(&self, node: &ast::StringLiteral, f: &mut PyFormatter) -> FormatResult<()> {
+        FormatNodeRule::<ast::StringLiteral>::fmt(self, node, f)
+    }
+}
+impl<'ast> AsFormat<PyFormatContext<'ast>> for ast::StringLiteral {
+    type Format<'a> = FormatRefWithRule<
+        'a,
+        ast::StringLiteral,
+        crate::other::string_literal::FormatStringLiteral,
+        PyFormatContext<'ast>,
+    >;
+    fn format(&self) -> Self::Format<'_> {
+        FormatRefWithRule::new(
+            self,
+            crate::other::string_literal::FormatStringLiteral::default(),
+        )
+    }
+}
+impl<'ast> IntoFormat<PyFormatContext<'ast>> for ast::StringLiteral {
+    type Format = FormatOwnedWithRule<
+        ast::StringLiteral,
+        crate::other::string_literal::FormatStringLiteral,
+        PyFormatContext<'ast>,
+    >;
+    fn into_format(self) -> Self::Format {
+        FormatOwnedWithRule::new(
+            self,
+            crate::other::string_literal::FormatStringLiteral::default(),
+        )
+    }
+}
+
 impl FormatRule<ast::BytesLiteral, PyFormatContext<'_>>
     for crate::other::bytes_literal::FormatBytesLiteral
 {

crates/ruff_python_formatter/src/other/f_string.rs

@@ -1,10 +1,12 @@
+use crate::prelude::*;
+use crate::preview::{
+    is_f_string_formatting_enabled, is_f_string_implicit_concatenated_string_literal_quotes_enabled,
+};
+use crate::string::{Quoting, StringNormalizer, StringQuotes};
 use ruff_formatter::write;
 use ruff_python_ast::{AnyStringFlags, FString, StringFlags};
 use ruff_source_file::Locator;
-
+use ruff_text_size::Ranged;
-use crate::prelude::*;
-use crate::preview::is_f_string_formatting_enabled;
-use crate::string::{Quoting, StringNormalizer, StringQuotes};
 
 use super::f_string_element::FormatFStringElement;
 
@@ -29,8 +31,17 @@ impl Format<PyFormatContext<'_>> for FormatFString<'_> {
     fn fmt(&self, f: &mut PyFormatter) -> FormatResult<()> {
         let locator = f.context().locator();
 
+        // If the preview style is enabled, make the decision on what quotes to use locally for each
+        // f-string instead of globally for the entire f-string expression.
+        let quoting =
+            if is_f_string_implicit_concatenated_string_literal_quotes_enabled(f.context()) {
+                f_string_quoting(self.value, &locator)
+            } else {
+                self.quoting
+            };
+
         let normalizer = StringNormalizer::from_context(f.context())
-            .with_quoting(self.quoting)
+            .with_quoting(quoting)
             .with_preferred_quote_style(f.options().quote_style());
 
         // If f-string formatting is disabled (not in preview), then we will
@@ -140,3 +151,20 @@ impl FStringLayout {
         matches!(self, FStringLayout::Multiline)
     }
 }
+
+fn f_string_quoting(f_string: &FString, locator: &Locator) -> Quoting {
+    let triple_quoted = f_string.flags.is_triple_quoted();
+
+    if f_string.elements.expressions().any(|expression| {
+        let string_content = locator.slice(expression.range());
+        if triple_quoted {
+            string_content.contains(r#"""""#) || string_content.contains("'''")
+        } else {
+            string_content.contains(['"', '\''])
+        }
+    }) {
+        Quoting::Preserve
+    } else {
+        Quoting::CanChange
+    }
+}

crates/ruff_python_formatter/src/other/f_string_part.rs

@@ -1,7 +1,7 @@
 use ruff_python_ast::FStringPart;
 
 use crate::other::f_string::FormatFString;
-use crate::other::string_literal::{FormatStringLiteral, StringLiteralKind};
+use crate::other::string_literal::StringLiteralKind;
 use crate::prelude::*;
 use crate::string::Quoting;
 
@@ -25,13 +25,12 @@ impl<'a> FormatFStringPart<'a> {
 impl Format<PyFormatContext<'_>> for FormatFStringPart<'_> {
     fn fmt(&self, f: &mut PyFormatter) -> FormatResult<()> {
         match self.part {
-            FStringPart::Literal(string_literal) => FormatStringLiteral::new(
+            #[allow(deprecated)]
-                string_literal,
+            FStringPart::Literal(string_literal) => string_literal
-                // If an f-string part is a string literal, the f-string is always
+                .format()
-                // implicitly concatenated e.g., `"foo" f"bar {x}"`. A standalone
+                .with_options(StringLiteralKind::InImplicitlyConcatenatedFString(
-                // string literal would be a string expression, not an f-string.
+                    self.quoting,
-                StringLiteralKind::InImplicitlyConcatenatedFString(self.quoting),
+                ))
-            )
                 .fmt(f),
             FStringPart::FString(f_string) => FormatFString::new(f_string, self.quoting).fmt(f),
         }

crates/ruff_python_formatter/src/other/string_literal.rs

@@ -1,23 +1,28 @@
+use ruff_formatter::FormatRuleWithOptions;
 use ruff_python_ast::StringLiteral;
 
 use crate::prelude::*;
+use crate::preview::is_f_string_implicit_concatenated_string_literal_quotes_enabled;
 use crate::string::{docstring, Quoting, StringNormalizer};
 use crate::QuoteStyle;
 
-pub(crate) struct FormatStringLiteral<'a> {
+#[derive(Default)]
-    value: &'a StringLiteral,
+pub struct FormatStringLiteral {
     layout: StringLiteralKind,
 }
 
-impl<'a> FormatStringLiteral<'a> {
+impl FormatRuleWithOptions<StringLiteral, PyFormatContext<'_>> for FormatStringLiteral {
-    pub(crate) fn new(value: &'a StringLiteral, layout: StringLiteralKind) -> Self {
+    type Options = StringLiteralKind;
-        Self { value, layout }
+
+    fn with_options(mut self, layout: StringLiteralKind) -> Self {
+        self.layout = layout;
+        self
     }
 }
 
 /// The kind of a string literal.
 #[derive(Copy, Clone, Debug, Default)]
-pub(crate) enum StringLiteralKind {
+pub enum StringLiteralKind {
     /// A normal string literal e.g., `"foo"`.
     #[default]
     String,
@@ -26,6 +31,8 @@ pub(crate) enum StringLiteralKind {
     /// A string literal that is implicitly concatenated with an f-string. This
     /// makes the overall expression an f-string whose quoting detection comes
     /// from the parent node (f-string expression).
+    #[deprecated]
+    #[allow(private_interfaces)]
     InImplicitlyConcatenatedFString(Quoting),
 }
 
@@ -36,16 +43,28 @@ impl StringLiteralKind {
     }
 
     /// Returns the quoting to be used for this string literal.
-    fn quoting(self) -> Quoting {
+    fn quoting(self, context: &PyFormatContext) -> Quoting {
         match self {
             StringLiteralKind::String | StringLiteralKind::Docstring => Quoting::CanChange,
-            StringLiteralKind::InImplicitlyConcatenatedFString(quoting) => quoting,
+            #[allow(deprecated)]
+            StringLiteralKind::InImplicitlyConcatenatedFString(quoting) => {
+                // Allow string literals to pick the "optimal" quote character
+                // even if any other fstring in the implicit concatenation uses an expression
+                // containing a quote character.
+                // TODO: Remove StringLiteralKind::InImplicitlyConcatenatedFString when promoting
+                //   this style to stable and remove the layout from `AnyStringPart::String`.
+                if is_f_string_implicit_concatenated_string_literal_quotes_enabled(context) {
+                    Quoting::CanChange
+                } else {
+                    quoting
+                }
+            }
         }
     }
 }
 
-impl Format<PyFormatContext<'_>> for FormatStringLiteral<'_> {
+impl FormatNodeRule<StringLiteral> for FormatStringLiteral {
-    fn fmt(&self, f: &mut PyFormatter) -> FormatResult<()> {
+    fn fmt_fields(&self, item: &StringLiteral, f: &mut PyFormatter) -> FormatResult<()> {
         let quote_style = f.options().quote_style();
         let quote_style = if self.layout.is_docstring() && !quote_style.is_preserve() {
             // Per PEP 8 and PEP 257, always prefer double quotes for docstrings,
@@ -56,9 +75,9 @@ impl Format<PyFormatContext<'_>> for FormatStringLiteral<'_> {
         };
 
         let normalized = StringNormalizer::from_context(f.context())
-            .with_quoting(self.layout.quoting())
+            .with_quoting(self.layout.quoting(f.context()))
             .with_preferred_quote_style(quote_style)
-            .normalize(self.value.into());
+            .normalize(item.into());
 
         if self.layout.is_docstring() {
             docstring::format(&normalized, f)

crates/ruff_python_formatter/src/preview.rs

@@ -19,6 +19,13 @@ pub(crate) fn is_f_string_formatting_enabled(context: &PyFormatContext) -> bool
     context.is_preview()
 }
 
+/// See [#13539](https://github.com/astral-sh/ruff/pull/13539)
+pub(crate) fn is_f_string_implicit_concatenated_string_literal_quotes_enabled(
+    context: &PyFormatContext,
+) -> bool {
+    context.is_preview()
+}
+
 pub(crate) fn is_with_single_item_pre_39_enabled(context: &PyFormatContext) -> bool {
     context.is_preview()
 }

crates/ruff_python_formatter/src/statement/suite.rs

@@ -11,7 +11,7 @@ use crate::comments::{
     leading_comments, trailing_comments, Comments, LeadingDanglingTrailingComments,
 };
 use crate::context::{NodeLevel, TopLevelStatementPosition, WithIndentLevel, WithNodeLevel};
-use crate::expression::expr_string_literal::ExprStringLiteralKind;
+use crate::other::string_literal::StringLiteralKind;
 use crate::prelude::*;
 use crate::statement::stmt_expr::FormatStmtExpr;
 use crate::verbatim::{
@@ -850,7 +850,7 @@ impl Format<PyFormatContext<'_>> for DocstringStmt<'_> {
                         .then_some(source_position(self.docstring.start())),
                     string_literal
                         .format()
-                        .with_options(ExprStringLiteralKind::Docstring),
+                        .with_options(StringLiteralKind::Docstring),
                     f.options()
                         .source_map_generation()
                         .is_enabled()

crates/ruff_python_formatter/src/string/any.rs

@@ -11,7 +11,7 @@ use ruff_text_size::{Ranged, TextRange};
 
 use crate::expression::expr_f_string::f_string_quoting;
 use crate::other::f_string::FormatFString;
-use crate::other::string_literal::{FormatStringLiteral, StringLiteralKind};
+use crate::other::string_literal::StringLiteralKind;
 use crate::prelude::*;
 use crate::string::Quoting;
 
@@ -160,6 +160,7 @@ impl<'a> Iterator for AnyStringPartsIter<'a> {
                 match part {
                     ast::FStringPart::Literal(string_literal) => AnyStringPart::String {
                         part: string_literal,
+                        #[allow(deprecated)]
                         layout: StringLiteralKind::InImplicitlyConcatenatedFString(*quoting),
                     },
                     ast::FStringPart::FString(f_string) => AnyStringPart::FString {
@@ -226,9 +227,7 @@ impl Ranged for AnyStringPart<'_> {
 impl Format<PyFormatContext<'_>> for AnyStringPart<'_> {
     fn fmt(&self, f: &mut PyFormatter) -> FormatResult<()> {
         match self {
-            AnyStringPart::String { part, layout } => {
+            AnyStringPart::String { part, layout } => part.format().with_options(*layout).fmt(f),
-                FormatStringLiteral::new(part, *layout).fmt(f)
-            }
             AnyStringPart::Bytes(bytes_literal) => bytes_literal.format().fmt(f),
             AnyStringPart::FString { part, quoting } => FormatFString::new(part, *quoting).fmt(f),
         }

crates/ruff_python_formatter/tests/snapshots/format@expression__fstring.py.snap

@@ -313,6 +313,14 @@ hello {
           ]
       } --------
 """
+
+
+# Implicit concatenated f-string containing quotes
+_ = (
+    'This string should change its quotes to double quotes'
+    f'This string uses double quotes in an expression {"woah"}'
+    f'This f-string does not use any quotes.'
+)
 ```
 
 ## Outputs
@@ -649,6 +657,14 @@ hello {
                 ]
             } --------
 """
+
+
+# Implicit concatenated f-string containing quotes
+_ = (
+    "This string should change its quotes to double quotes"
+    f'This string uses double quotes in an expression {"woah"}'
+    f"This f-string does not use any quotes."
+)
 ```
 
 
@@ -973,6 +989,14 @@ hello {
           ]
       } --------
 """
+
+
+# Implicit concatenated f-string containing quotes
+_ = (
+    'This string should change its quotes to double quotes'
+    f'This string uses double quotes in an expression {"woah"}'
+    f'This f-string does not use any quotes.'
+)
 ```
 
 
@@ -1279,7 +1303,7 @@ hello {
      # comment 27
      # comment 28
  } woah {x}"
-@@ -287,19 +299,19 @@
+@@ -287,27 +299,27 @@
          if indent2:
              foo = f"""hello world
  hello {
@@ -1314,4 +1338,14 @@ hello {
 +                ]
 +            } --------
  """
+ 
+ 
+ # Implicit concatenated f-string containing quotes
+ _ = (
+-    'This string should change its quotes to double quotes'
++    "This string should change its quotes to double quotes"
+     f'This string uses double quotes in an expression {"woah"}'
+-    f'This f-string does not use any quotes.'
++    f"This f-string does not use any quotes."
+ )
 ```