Merge pull request #4449 from harupy/fix-dict-spread-in-dict

Fix AST generated from a dict literal containing dict unpacking

ast/asdl_rs.py

@@ -227,20 +227,25 @@ def visitConstructor(self, cons, parent, depth):
         if cons.fields:
             self.emit(f"{cons.name} {{", depth)
             for f in cons.fields:
-                self.visit(f, parent, "", depth + 1)
+                self.visit(f, parent, "", depth + 1, cons.name)
             self.emit("},", depth)
         else:
             self.emit(f"{cons.name},", depth)
 
-    def visitField(self, field, parent, vis, depth):
+    def visitField(self, field, parent, vis, depth, constructor=None):
         typ = get_rust_type(field.type)
         fieldtype = self.typeinfo.get(field.type)
         if fieldtype and fieldtype.has_userdata:
             typ = f"{typ}<U>"
         # don't box if we're doing Vec<T>, but do box if we're doing Vec<Option<Box<T>>>
         if fieldtype and fieldtype.boxed and (not (parent.product or field.seq) or field.opt):
             typ = f"Box<{typ}>"
-        if field.opt:
+        if field.opt or (
+            # When a dictionary literal contains dictionary unpacking (e.g., `{**d}`),
+            # the expression to be unpacked goes in `values` with a `None` at the corresponding
+            # position in `keys`. To handle this, the type of `keys` needs to be `Option<Vec<T>>`.
+            constructor == "Dict" and field.name == "keys"
+        ):
             typ = f"Option<{typ}>"
         if field.seq:
             typ = f"Vec<{typ}>"

ast/src/ast_gen.rs

@@ -195,7 +195,7 @@ pub enum ExprKind<U = ()> {
         orelse: Box<Expr<U>>,
     },
     Dict {
-        keys: Vec<Expr<U>>,
+        keys: Vec<Option<Expr<U>>>,
         values: Vec<Expr<U>>,
     },
     Set {

ast/src/unparse.rs

@@ -152,7 +152,11 @@ impl<'a> Unparser<'a> {
                 let (packed, unpacked) = values.split_at(keys.len());
                 for (k, v) in keys.iter().zip(packed) {
                     self.p_delim(&mut first, ", ")?;
-                    write!(self, "{}: {}", *k, *v)?;
+                    if let Some(k) = k {
+                        write!(self, "{}: {}", *k, *v)?;
+                    } else {
+                        write!(self, "**{}", *v)?;
+                    }
                 }
                 for d in unpacked {
                     self.p_delim(&mut first, ", ")?;

parser/python.lalrpop

@@ -1136,44 +1136,11 @@ Atom<Goal>: ast::Expr = {
         }.into())
     },
     <location:@L> "{" <e:DictLiteralValues?> "}" <end_location:@R> => {
-        let pairs = e.unwrap_or_default();
-
-        let (keys, values) = match pairs.iter().position(|(k,_)| k.is_none()) {
-            Some(unpack_idx) => {
-                let mut pairs = pairs;
-                let (keys, mut values): (_, Vec<_>) = pairs.drain(..unpack_idx).map(|(k, v)| (*k.unwrap(), v)).unzip();
-
-                fn build_map(items: &mut Vec<(ast::Expr, ast::Expr)>) -> ast::Expr {
-                    let location = items[0].0.location;
-                    let end_location = items[0].0.end_location;
-                    let (keys, values) = items.drain(..).unzip();
-                    ast::Expr {
-                        location,
-                        end_location,
-                        custom: (),
-                        node: ast::ExprKind::Dict { keys, values }
-                    }
-                }
-
-                let mut items = Vec::new();
-                for (key, value) in pairs.into_iter() {
-                    if let Some(key) = key {
-                        items.push((*key, value));
-                        continue;
-                    }
-                    if !items.is_empty() {
-                        values.push(build_map(&mut items));
-                    }
-                    values.push(value);
-                }
-                if !items.is_empty() {
-                    values.push(build_map(&mut items));
-                }
-                (keys, values)
-            },
-            None => pairs.into_iter().map(|(k, v)| (*k.unwrap(), v)).unzip()
-        };
-
+        let (keys, values) = e
+            .unwrap_or_default()
+            .into_iter()
+            .map(|(k, v)| (k.map(|x| *x), v))
+            .unzip();
         ast::Expr {
             location,
             end_location: Some(end_location),

parser/src/parser.rs

@@ -309,4 +309,10 @@ with (0 as a, 1 as b,): pass
             assert!(parse_program(source, "<test>").is_err());
         }
     }
+
+    #[test]
+    fn test_dict_unpacking() {
+        let parse_ast = parse_expression(r#"{"a": "b", **c, "d": "e"}"#, "<test>").unwrap();
+        insta::assert_debug_snapshot!(parse_ast);
+    }
 }

parser/src/snapshots/rustpython_parser__parser__tests__dict_unpacking.snap

@@ -0,0 +1,121 @@
+---
+source: compiler/parser/src/parser.rs
+expression: parse_ast
+---
+Located {
+    location: Location {
+        row: 1,
+        column: 0,
+    },
+    end_location: Some(
+        Location {
+            row: 1,
+            column: 25,
+        },
+    ),
+    custom: (),
+    node: Dict {
+        keys: [
+            Some(
+                Located {
+                    location: Location {
+                        row: 1,
+                        column: 1,
+                    },
+                    end_location: Some(
+                        Location {
+                            row: 1,
+                            column: 4,
+                        },
+                    ),
+                    custom: (),
+                    node: Constant {
+                        value: Str(
+                            "a",
+                        ),
+                        kind: None,
+                    },
+                },
+            ),
+            None,
+            Some(
+                Located {
+                    location: Location {
+                        row: 1,
+                        column: 16,
+                    },
+                    end_location: Some(
+                        Location {
+                            row: 1,
+                            column: 19,
+                        },
+                    ),
+                    custom: (),
+                    node: Constant {
+                        value: Str(
+                            "d",
+                        ),
+                        kind: None,
+                    },
+                },
+            ),
+        ],
+        values: [
+            Located {
+                location: Location {
+                    row: 1,
+                    column: 6,
+                },
+                end_location: Some(
+                    Location {
+                        row: 1,
+                        column: 9,
+                    },
+                ),
+                custom: (),
+                node: Constant {
+                    value: Str(
+                        "b",
+                    ),
+                    kind: None,
+                },
+            },
+            Located {
+                location: Location {
+                    row: 1,
+                    column: 13,
+                },
+                end_location: Some(
+                    Location {
+                        row: 1,
+                        column: 14,
+                    },
+                ),
+                custom: (),
+                node: Name {
+                    id: "c",
+                    ctx: Load,
+                },
+            },
+            Located {
+                location: Location {
+                    row: 1,
+                    column: 21,
+                },
+                end_location: Some(
+                    Location {
+                        row: 1,
+                        column: 24,
+                    },
+                ),
+                custom: (),
+                node: Constant {
+                    value: Str(
+                        "e",
+                    ),
+                    kind: None,
+                },
+            },
+        ],
+    },
+}