Support concatenated literals in format-literals (#4974)

crates/ruff/resources/test/fixtures/pyupgrade/UP030_0.py

@@ -21,10 +21,6 @@ x = "foo {0}" \
 
 "\N{snowman} {0}".format(1)
 
-'{' '0}'.format(1)
-
-# These will not change because we are waiting for libcst to fix this issue:
-# https://github.com/Instagram/LibCST/issues/846
 print(
     'foo{0}'
     'bar{1}'.format(1, 2)
@@ -34,3 +30,5 @@ print(
     'foo{0}'  # ohai\n"
     'bar{1}'.format(1, 2)
 )
+
+'{' '0}'.format(1)

crates/ruff/resources/test/fixtures/pyupgrade/UP030_1.py

@@ -13,3 +13,5 @@ f"{0}".format(a)
 f"{0}".format(1)
 
 print(f"{0}".format(1))
+
+''.format(1)

crates/ruff/src/rules/pyupgrade/rules/format_literals.rs

@@ -1,14 +1,14 @@
-use anyhow::{anyhow, bail, Result};
-use libcst_native::Arg;
+use anyhow::{anyhow, Result};
+use libcst_native::{Arg, Expression};
 use once_cell::sync::Lazy;
 use regex::Regex;
 use rustpython_parser::ast::{Expr, Ranged};
 
-use crate::autofix::codemods::CodegenStylist;
 use ruff_diagnostics::{AutofixKind, Diagnostic, Edit, Fix, Violation};
 use ruff_macros::{derive_message_formats, violation};
 use ruff_python_ast::source_code::{Locator, Stylist};
 
+use crate::autofix::codemods::CodegenStylist;
 use crate::checkers::ast::Checker;
 use crate::cst::matchers::{match_attribute, match_call_mut, match_expression};
 use crate::registry::AsRule;
@@ -35,29 +35,51 @@ impl Violation for FormatLiterals {
 static FORMAT_SPECIFIER: Lazy<Regex> =
     Lazy::new(|| Regex::new(r"\{(?P<int>\d+)(?P<fmt>.*?)}").unwrap());
 
-/// Returns a string without the format specifiers.
-/// Ex. "Hello {0} {1}" -> "Hello {} {}"
-fn remove_specifiers(raw_specifiers: &str) -> String {
-    FORMAT_SPECIFIER
-        .replace_all(raw_specifiers, "{$fmt}")
-        .to_string()
+/// Remove the explicit positional indices from a format string.
+fn remove_specifiers<'a>(value: &mut Expression<'a>, arena: &'a mut typed_arena::Arena<String>) {
+    match value {
+        Expression::SimpleString(expr) => {
+            expr.value = arena.alloc(
+                FORMAT_SPECIFIER
+                    .replace_all(expr.value, "{$fmt}")
+                    .to_string(),
+            );
+        }
+        Expression::ConcatenatedString(expr) => {
+            let mut stack = vec![&mut expr.left, &mut expr.right];
+            while let Some(string) = stack.pop() {
+                match string.as_mut() {
+                    libcst_native::String::Simple(string) => {
+                        string.value = arena.alloc(
+                            FORMAT_SPECIFIER
+                                .replace_all(string.value, "{$fmt}")
+                                .to_string(),
+                        );
+                    }
+                    libcst_native::String::Concatenated(string) => {
+                        stack.push(&mut string.left);
+                        stack.push(&mut string.right);
+                    }
+                    libcst_native::String::Formatted(_) => {}
+                }
+            }
+        }
+        _ => {}
+    }
 }
 
 /// Return the corrected argument vector.
-fn generate_arguments<'a>(
-    old_args: &[Arg<'a>],
-    correct_order: &'a [usize],
-) -> Result<Vec<Arg<'a>>> {
-    let mut new_args: Vec<Arg> = Vec::with_capacity(old_args.len());
-    for (idx, given) in correct_order.iter().enumerate() {
+fn generate_arguments<'a>(arguments: &[Arg<'a>], order: &'a [usize]) -> Result<Vec<Arg<'a>>> {
+    let mut new_arguments: Vec<Arg> = Vec::with_capacity(arguments.len());
+    for (idx, given) in order.iter().enumerate() {
         // We need to keep the formatting in the same order but move the values.
-        let values = old_args
+        let values = arguments
             .get(*given)
             .ok_or_else(|| anyhow!("Failed to extract argument at: {given}"))?;
-        let formatting = old_args
+        let formatting = arguments
             .get(idx)
             .ok_or_else(|| anyhow!("Failed to extract argument at: {idx}"))?;
-        let new_arg = Arg {
+        let argument = Arg {
             value: values.value.clone(),
             comma: formatting.comma.clone(),
             equal: None,
@@ -66,19 +88,14 @@ fn generate_arguments<'a>(
             whitespace_after_star: formatting.whitespace_after_star.clone(),
             whitespace_after_arg: formatting.whitespace_after_arg.clone(),
         };
-        new_args.push(new_arg);
+        new_arguments.push(argument);
     }
-    Ok(new_args)
+    Ok(new_arguments)
 }
 
 /// Returns true if the indices are sequential.
 fn is_sequential(indices: &[usize]) -> bool {
-    for (expected, actual) in indices.iter().enumerate() {
-        if expected != *actual {
-            return false;
-        }
-    }
-    true
+    indices.iter().enumerate().all(|(idx, value)| idx == *value)
 }
 
 /// Returns the corrected function call.
@@ -88,28 +105,32 @@ fn generate_call(
     locator: &Locator,
     stylist: &Stylist,
 ) -> Result<String> {
-    let module_text = locator.slice(expr.range());
-    let mut expression = match_expression(module_text)?;
-    let call = match_call_mut(&mut expression)?;
+    let content = locator.slice(expr.range());
+    let parenthesized_content = format!("({content})");
+    let mut expression = match_expression(&parenthesized_content)?;
 
     // Fix the call arguments.
+    let call = match_call_mut(&mut expression)?;
     if !is_sequential(correct_order) {
         call.args = generate_arguments(&call.args, correct_order)?;
     }
 
     // Fix the string itself.
     let item = match_attribute(&mut call.func)?;
+    let mut arena = typed_arena::Arena::new();
+    remove_specifiers(&mut item.value, &mut arena);
 
-    let cleaned = remove_specifiers(&item.codegen_stylist(stylist));
+    // Remove the parentheses (first and last characters).
+    let mut output = expression.codegen_stylist(stylist);
+    output.remove(0);
+    output.pop();
 
-    call.func = Box::new(match_expression(&cleaned)?);
-
-    let state = expression.codegen_stylist(stylist);
-    if module_text == state {
-        // Ex) `'{' '0}'.format(1)`
-        bail!("Failed to generate call expression for: {module_text}")
+    // Ex) `'{' '0}'.format(1)`
+    if output == content {
+        return Err(anyhow!("Unable to identify format literals"));
     }
-    Ok(state)
+
+    Ok(output)
 }
 
 /// UP030
@@ -124,23 +145,21 @@ pub(crate) fn format_literals(checker: &mut Checker, summary: &FormatSummary, ex
     if !summary.autos.is_empty() {
         return;
     }
-    if !(0..summary.indices.len()).all(|index| summary.indices.contains(&index)) {
+    if summary.indices.is_empty() {
+        return;
+    }
+    if (0..summary.indices.len()).any(|index| !summary.indices.contains(&index)) {
         return;
     }
 
     let mut diagnostic = Diagnostic::new(FormatLiterals, expr.range());
     if checker.patch(diagnostic.kind.rule()) {
-        // Currently, the only issue we know of is in LibCST:
-        // https://github.com/Instagram/LibCST/issues/846
-        if let Ok(contents) =
-            generate_call(expr, &summary.indices, checker.locator, checker.stylist)
-        {
-            #[allow(deprecated)]
-            diagnostic.set_fix(Fix::unspecified(Edit::range_replacement(
-                contents,
+        diagnostic.try_set_fix(|| {
+            Ok(Fix::suggested(Edit::range_replacement(
+                generate_call(expr, &summary.indices, checker.locator, checker.stylist)?,
                 expr.range(),
-            )));
-        };
+            )))
+        });
     }
     checker.diagnostics.push(diagnostic);
 }

crates/ruff/src/rules/pyupgrade/snapshots/ruff__rules__pyupgrade__tests__UP030_0.py.snap

@@ -183,7 +183,7 @@ UP030_0.py:22:1: UP030 [*] Use implicit references for positional format fields
 24 | "\N{snowman} {0}".format(1)
    | ^^^^^^^^^^^^^^^^^^^^^^^^^^^ UP030
 25 | 
-26 | '{' '0}'.format(1)
+26 | print(
    |
    = help: Remove explicit positional indices
 
@@ -194,25 +194,36 @@ UP030_0.py:22:1: UP030 [*] Use implicit references for positional format fields
 22    |-"\N{snowman} {0}".format(1)
    22 |+"\N{snowman} {}".format(1)
 23 23 | 
-24 24 | '{' '0}'.format(1)
-25 25 | 
+24 24 | print(
+25 25 |     'foo{0}'
 
-UP030_0.py:24:1: UP030 Use implicit references for positional format fields
+UP030_0.py:25:5: UP030 [*] Use implicit references for positional format fields
    |
-24 | "\N{snowman} {0}".format(1)
-25 | 
-26 | '{' '0}'.format(1)
-   | ^^^^^^^^^^^^^^^^^^ UP030
-27 | 
-28 | # These will not change because we are waiting for libcst to fix this issue:
+25 |   print(
+26 |       'foo{0}'
+   |  _____^
+27 | |     'bar{1}'.format(1, 2)
+   | |_________________________^ UP030
+28 |   )
    |
    = help: Remove explicit positional indices
 
-UP030_0.py:29:5: UP030 Use implicit references for positional format fields
+ℹ Suggested fix
+22 22 | "\N{snowman} {0}".format(1)
+23 23 | 
+24 24 | print(
+25    |-    'foo{0}'
+26    |-    'bar{1}'.format(1, 2)
+   25 |+    'foo{}'
+   26 |+    'bar{}'.format(1, 2)
+27 27 | )
+28 28 | 
+29 29 | print(
+
+UP030_0.py:30:5: UP030 [*] Use implicit references for positional format fields
    |
-29 |   # https://github.com/Instagram/LibCST/issues/846
 30 |   print(
-31 |       'foo{0}'
+31 |       'foo{0}'  # ohai\n"
    |  _____^
 32 | |     'bar{1}'.format(1, 2)
    | |_________________________^ UP030
@@ -220,14 +231,24 @@ UP030_0.py:29:5: UP030 Use implicit references for positional format fields
    |
    = help: Remove explicit positional indices
 
-UP030_0.py:34:5: UP030 Use implicit references for positional format fields
+ℹ Suggested fix
+27 27 | )
+28 28 | 
+29 29 | print(
+30    |-    'foo{0}'  # ohai\n"
+31    |-    'bar{1}'.format(1, 2)
+   30 |+    'foo{}'  # ohai\n"
+   31 |+    'bar{}'.format(1, 2)
+32 32 | )
+33 33 | 
+34 34 | '{' '0}'.format(1)
+
+UP030_0.py:34:1: UP030 Use implicit references for positional format fields
    |
-34 |   print(
-35 |       'foo{0}'  # ohai\n"
-   |  _____^
-36 | |     'bar{1}'.format(1, 2)
-   | |_________________________^ UP030
-37 |   )
+34 | )
+35 | 
+36 | '{' '0}'.format(1)
+   | ^^^^^^^^^^^^^^^^^^ UP030
    |
    = help: Remove explicit positional indices