fix: cover more extreme edge cases for f-string

Cargo.toml

@@ -15,6 +15,6 @@ rustpython-literal = ">=0.4.0"
 
 [dev-dependencies]
 rustpython-parser = "0.4.0"
-rustpython-ast = { version = "0.4.0", features = ["fold"] }
+rustpython-ast = { version = "0.4.0", features = ["fold", "unparse"] }
 rand = "0.8.5"
 pretty_assertions = "1.4.1"

src/lib.rs

@@ -1,5 +1,5 @@
 pub mod unparser;
-
+mod utils;
 pub use crate::unparser::Unparser;
 
 #[cfg(test)]

src/unparser.rs

@@ -16,6 +16,8 @@ use rustpython_ast::{
 use rustpython_ast::{Constant, ConversionFlag, Int};
 use std::ops::Deref;
 
+use crate::utils::replace_first_and_last;
+
 enum Precedence {
     NamedExpr = 1,
     Tuple = 2,
@@ -986,6 +988,8 @@ impl Unparser {
             self.write_str("f");
         }
         let mut expr_source = String::new();
+
+        let mut formatted_values_sources: Vec<String> = Vec::new();
         for expr in node.values.iter() {
             let mut inner_unparser = Unparser::new();
             match expr {
@@ -996,22 +1000,50 @@ impl Unparser {
                     } else {
                         unreachable!()
                     }
+                    expr_source += inner_unparser.source.as_str();
+                }
+                Expr::FormattedValue(formatted) => {
+                    expr_source += &("{".to_owned()
+                        + formatted_values_sources.len().to_string().as_str()
+                        + "}");
+                    inner_unparser.unparse_expr_formatted_value(formatted);
+                    formatted_values_sources.push(inner_unparser.source);
                 }
                 _ => {
                     inner_unparser.unparse_expr(expr);
+                    expr_source += inner_unparser.source.as_str();
                 }
             }
-
-            expr_source += inner_unparser.source.as_str();
         }
 
         if is_spec {
+            for (i, formatted) in formatted_values_sources.iter().enumerate() {
+                let to_replace = "{".to_owned() + i.to_string().as_str() + "}";
+                expr_source = expr_source.replace(&to_replace, formatted)
+            }
             self.write_str(&expr_source);
         } else {
-            let escaped_source = rustpython_literal::escape::UnicodeEscape::new_repr(&expr_source)
-                .str_repr()
-                .to_string()
-                .unwrap();
+            let mut escaped_source =
+                rustpython_literal::escape::UnicodeEscape::new_repr(&expr_source)
+                    .str_repr()
+                    .to_string()
+                    .unwrap();
+            for (i, formatted) in formatted_values_sources.iter().enumerate() {
+                let to_replace = "{".to_owned() + i.to_string().as_str() + "}";
+                escaped_source = escaped_source.replace(&to_replace, formatted)
+            }
+
+            let has_single = escaped_source.contains("'");
+            let has_double = escaped_source.contains("\"");
+            let has_single_doc = escaped_source.contains("'''");
+            if has_single && has_double && has_single_doc {
+                escaped_source = replace_first_and_last(&escaped_source, "\"\"\"")
+            } else if has_single && has_double {
+                escaped_source = replace_first_and_last(&escaped_source, "'''")
+            } else if has_single {
+                escaped_source = replace_first_and_last(&escaped_source, "\"")
+            }
+
             self.write_str(&escaped_source);
         }
     }

src/utils.rs

@@ -0,0 +1,9 @@
+pub fn replace_first_and_last(s: &str, replacement: &str) -> String {
+    if s.len() <= 1 {
+        return replacement.to_string() + replacement;
+    }
+
+    let middle = &s[1..s.len() - 1];
+
+    format!("{}{}{}", replacement, middle, replacement)
+}

test_files/f_string.py

@@ -0,0 +1,22 @@
+world = "World"
+empty_f_string = f""  # noqa: F541
+f"{world!a:}None{empty_f_string!s:}None"
+answer = 42.000001
+f"{answer:.03f}"
+f"'\"'''\"\"\"{{}}\\"  # noqa
+if __name__ == "__main__":
+    print(f"Hello {world}!")
+
+# fmt: off
+lines = "\n".join(
+            f'''<clipPath id="{unique_id}-line-{line_no}">{make_tag({"rect"}, x=0, y=offset, width=char_width * width, height=line_height + 0.25)}</clipPath>''' # noqa
+            for line_no, offset in enumerate(line_offsets) # noqa
+        )
+
+tag_attribs = " ".join(
+    (
+        f'''{k.lstrip('_').replace('_', '-')}="{stringify(v)}"''' # noqa
+        for (k, v) in attribs.items() # noqa
+    )
+)
+# fmt: on