feat(prettier): check parens for (let)[a] = 1 (#1585)

crates/oxc_ast/src/ast/js.rs

@@ -1248,6 +1248,13 @@ impl<'a> ForStatementInit<'a> {
     pub fn is_lexical_declaration(&self) -> bool {
         matches!(self, Self::VariableDeclaration(decl) if decl.kind.is_lexical())
     }
+
+    pub fn expression(&self) -> Option<&Expression<'a>> {
+        match self {
+            Self::Expression(e) => Some(e),
+            _ => None,
+        }
+    }
 }
 
 /// For-In Statement

crates/oxc_prettier/src/format/mod.rs

@@ -28,7 +28,7 @@ use std::borrow::Cow;
 use oxc_allocator::{Box, Vec};
 use oxc_ast::{ast::*, AstKind};
 use oxc_span::GetSpan;
-use oxc_syntax::identifier::is_identify_name;
+use oxc_syntax::identifier::is_identifier_name;
 
 use crate::{
     array,
@@ -95,8 +95,8 @@ impl<'a> Format<'a> for Directive {
             self.expression.value.as_str(),
             p.options.single_quote,
         )));
-        if p.options.semi {
-            parts.push(ss!(";"));
+        if let Some(semi) = p.semi() {
+            parts.push(semi);
         }
         parts.extend(hardline!());
         Doc::Array(parts)
@@ -135,8 +135,8 @@ impl<'a> Format<'a> for ExpressionStatement<'a> {
         wrap!(p, self, ExpressionStatement, {
             let mut parts = p.vec();
             parts.push(self.expression.format(p));
-            if p.options.semi {
-                parts.push(ss!(";"));
+            if let Some(semi) = p.semi() {
+                parts.push(semi);
             }
             Doc::Array(parts)
         })
@@ -363,8 +363,8 @@ impl<'a> Format<'a> for DoWhileStatement<'a> {
             parts.push(ss!("while ("));
             parts.push(group!(p, indent!(p, softline!(), format!(p, self.test)), softline!()));
             parts.push(ss!(")"));
-            if p.options.semi {
-                parts.push(ss!(";"));
+            if let Some(semi) = p.semi() {
+                parts.push(semi);
             }
 
             Doc::Array(parts)
@@ -651,7 +651,9 @@ impl<'a> Format<'a> for VariableDeclaration<'a> {
             }));
 
             if !parent_for_loop.is_some_and(|span| span != self.span) {
-                parts.push(ss!(";"));
+                if let Some(semi) = p.semi() {
+                    parts.push(semi);
+                }
             }
 
             Doc::Group(Group::new(parts, false))
@@ -674,8 +676,8 @@ impl<'a> Format<'a> for TSTypeAliasDeclaration<'a> {
         parts.push(ss!(" = "));
         parts.push(format!(p, self.type_annotation));
 
-        if p.options.semi {
-            parts.push(ss!(";"));
+        if let Some(semi) = p.semi() {
+            parts.push(semi);
         }
 
         Doc::Array(parts)
@@ -1047,8 +1049,8 @@ impl<'a> Format<'a> for ImportDeclaration<'a> {
         }
         parts.push(ss!(" from "));
         parts.push(self.source.format(p));
-        if p.options.semi {
-            parts.push(ss!(";"));
+        if let Some(semi) = p.semi() {
+            parts.push(semi);
         }
         Doc::Array(parts)
     }
@@ -1223,7 +1225,7 @@ impl<'a> Format<'a> for Expression<'a> {
 
 impl<'a> Format<'a> for IdentifierReference {
     fn format(&self, p: &mut Prettier<'a>) -> Doc<'a> {
-        p.str(self.name.as_str())
+        wrap!(p, self, IdentifierReference, { p.str(self.name.as_str()) })
     }
 }
 
@@ -1551,7 +1553,7 @@ impl<'a> Format<'a> for PropertyKey<'a> {
                         let unquote = if need_quote {
                             false
                         } else {
-                            is_identify_name(literal.value.as_str())
+                            is_identifier_name(literal.value.as_str())
                         };
 
                         if !unquote || p.options.quote_props.is_preserve() {

crates/oxc_prettier/src/format/property.rs

@@ -1,12 +1,12 @@
 use oxc_ast::ast::{Expression, PropertyKey};
-use oxc_syntax::identifier::is_identify_name;
+use oxc_syntax::identifier::is_identifier_name;
 
 pub(super) fn is_property_key_has_quote(key: &PropertyKey<'_>) -> bool {
     matches!(key, PropertyKey::Expression(Expression::StringLiteral(literal)) if is_string_prop_safe_to_unquote(literal.value.as_str()))
 }
 
 pub(super) fn is_string_prop_safe_to_unquote(value: &str) -> bool {
-    !is_identify_name(value) && !is_simple_number(value)
+    !is_identifier_name(value) && !is_simple_number(value)
 }
 
 // Matches “simple” numbers like `123` and `2.5` but not `1_000`, `1e+100` or `0b10`.

crates/oxc_prettier/src/lib.rs

@@ -121,6 +121,10 @@ impl<'a> Prettier<'a> {
         unsafe { std::mem::transmute(t) }
     }
 
+    pub fn semi(&self) -> Option<Doc<'a>> {
+        self.options.semi.then(|| Doc::Str(";"))
+    }
+
     pub fn should_print_es5_comma(&self) -> bool {
         self.should_print_comma_impl(false)
     }

crates/oxc_prettier/src/needs_parens.rs

@@ -11,7 +11,8 @@
 use oxc_ast::{
     ast::{
         AssignmentTarget, AssignmentTargetPattern, ChainElement, ExportDefaultDeclarationKind,
-        Expression, ModuleDeclaration, ObjectExpression, SimpleAssignmentTarget,
+        Expression, ForStatementLeft, MemberExpression, ModuleDeclaration, ObjectExpression,
+        SimpleAssignmentTarget,
     },
     AstKind,
 };
@@ -30,34 +31,23 @@ impl<'a> Prettier<'a> {
     }
 
     fn need_parens(&mut self, kind: AstKind<'a>) -> bool {
-        if matches!(kind, AstKind::Program(_)) {
+        if matches!(kind, AstKind::Program(_)) || kind.is_statement() || kind.is_declaration() {
             return false;
         }
 
-        if kind.is_statement() || kind.is_declaration() {
-            return false;
-        }
-
-        let parent_kind = self.parent_kind();
-
-        if let AstKind::ObjectExpression(e) = kind {
-            if self.check_object_expression(e) {
-                return true;
-            }
-        }
-
-        if self.check_parent_kind(kind, parent_kind) {
-            return true;
-        }
-
-        if self.check_kind(kind, parent_kind) {
+        if matches!(kind, AstKind::ObjectExpression(e) if self.check_object_expression(e))
+            || self.check_let_object(kind)
+            || self.check_parent_kind(kind)
+            || self.check_kind(kind)
+        {
             return true;
         }
 
         false
     }
 
-    fn check_kind(&self, kind: AstKind<'a>, parent_kind: AstKind<'a>) -> bool {
+    fn check_kind(&self, kind: AstKind<'a>) -> bool {
+        let parent_kind = self.parent_kind();
         match kind {
             AstKind::NumberLiteral(literal) => {
                 matches!(parent_kind, AstKind::MemberExpression(e) if e.object().span() == literal.span)
@@ -190,8 +180,8 @@ impl<'a> Prettier<'a> {
         }
     }
 
-    fn check_parent_kind(&mut self, kind: AstKind<'a>, parent_kind: AstKind<'a>) -> bool {
-        match parent_kind {
+    fn check_parent_kind(&mut self, kind: AstKind<'a>) -> bool {
+        match self.parent_kind() {
             AstKind::Class(class) => {
                 if let Some(h) = &class.super_class {
                     match kind {
@@ -263,6 +253,54 @@ impl<'a> Prettier<'a> {
         false
     }
 
+    /// `(let)[a] = 1`
+    fn check_let_object(&self, kind: AstKind<'a>) -> bool {
+        let AstKind::IdentifierReference(ident) = kind else { return false };
+        if ident.name != "let" {
+            return false;
+        }
+        let AstKind::MemberExpression(MemberExpression::ComputedMemberExpression(expr)) =
+            self.parent_kind()
+        else {
+            return false;
+        };
+        if !matches!(&expr.object, Expression::Identifier(ident) if ident.name == "let") {
+            return false;
+        }
+        let Some(statement) = self.nodes.iter().rev().find(|node| {
+            matches!(
+                node,
+                AstKind::ExpressionStatement(_)
+                    | AstKind::ForStatement(_)
+                    | AstKind::ForInStatement(_)
+            )
+        }) else {
+            return false;
+        };
+        match statement {
+            AstKind::ExpressionStatement(stmt) => {
+                Self::starts_with_no_lookahead_token(&stmt.expression, ident.span)
+            }
+            AstKind::ForStatement(stmt) => stmt
+                .init
+                .as_ref()
+                .and_then(|init| init.expression())
+                .map_or(false, |e| Self::starts_with_no_lookahead_token(e, ident.span)),
+            AstKind::ForInStatement(stmt) => {
+                if let ForStatementLeft::AssignmentTarget(
+                    AssignmentTarget::SimpleAssignmentTarget(
+                        SimpleAssignmentTarget::MemberAssignmentTarget(e),
+                    ),
+                ) = &stmt.left
+                {
+                    return Self::starts_with_no_lookahead_token(e.object(), ident.span);
+                }
+                false
+            }
+            _ => false,
+        }
+    }
+
     fn check_object_function_class(&self, span: Span) -> bool {
         for ast_kind in self.nodes.iter().rev() {
             if let AstKind::ExpressionStatement(e) = ast_kind {

crates/oxc_syntax/src/identifier.rs

@@ -109,7 +109,7 @@ pub fn is_identifier_part(c: char) -> bool {
     is_id_continue_unicode(c) || c == ZWNJ || c == ZWJ
 }
 
-pub fn is_identify_name(name: &str) -> bool {
+pub fn is_identifier_name(name: &str) -> bool {
     let mut chars = name.chars();
     chars.next().is_some_and(is_identifier_start_all) && chars.all(is_identifier_part)
 }

tasks/prettier_conformance/prettier.snap.md

@@ -1,4 +1,4 @@
-Compatibility: 201/561 (35.83%)
+Compatibility: 203/561 (36.19%)
 
 # Failed
 
@@ -157,7 +157,6 @@ Compatibility: 201/561 (35.83%)
 * comments/jsdoc.js
 * comments/jsx.js
 * comments/last-arg.js
-* comments/multi-comments-2.js
 * comments/multi-comments-on-same-line-2.js
 * comments/multi-comments-on-same-line.js
 * comments/multi-comments.js
@@ -277,7 +276,6 @@ Compatibility: 201/561 (35.83%)
 * identifier/for-of/let.js
 
 ### identifier/parentheses
-* identifier/parentheses/const.js
 * identifier/parentheses/let.js
 
 ### if