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Merged
Jarred-Sumner merged 14 commits into from
Feb 10, 2026
Merged

feat(transpiler): implement TC39 standard ES decorators lowering #26436

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499d2d3
feat(transpiler): implement TC39 standard ES decorators lowering
Jarred-Sumner Jan 25, 2026
e0c5e03
refactor(transpiler): extract decorator lowering into lowerDecorators…
Jarred-Sumner Jan 25, 2026
bff4726
[autofix.ci] apply automated fixes
autofix-ci[bot] Jan 25, 2026
90d20c6
fix(test): copy esbuild decorator tests into test dir for CI
Jarred-Sumner Jan 25, 2026
f621bab
fix(transpiler): address review feedback for ES decorators
Jarred-Sumner Jan 25, 2026
3048ff4
fix(test): clean up esbuild decorator test boilerplate
Jarred-Sumner Jan 25, 2026
3f89145
fix(test): update snapshot for cyclic-imports-async-bundler test
Jarred-Sumner Jan 25, 2026
02d6a87
fix(test): update snapshots and add experimentalDecorators to legacy …
Jarred-Sumner Jan 25, 2026
0131156
fix(transpiler): fix export default class crash and accessor ! parsin…
Jarred-Sumner Jan 28, 2026
c5f6b24
fix(transpiler): improve decorator lowering robustness
Jarred-Sumner Jan 28, 2026
20c47da
fix(transpiler): complete rewriteStmts coverage and use innerIndex() …
Jarred-Sumner Jan 28, 2026
9dc410b
Merge branch 'main' into jarred/esdecorator
dylan-conway Jan 30, 2026
42df22a
Merge branch 'main' into jarred/esdecorator
Jarred-Sumner Feb 9, 2026
cbeeec9
Update html-import-manifest.test.ts
Jarred-Sumner Feb 10, 2026
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2 changes: 2 additions & 0 deletions src/ast/G.zig
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Original file line number Diff line number Diff line change
Expand Up @@ -32,6 +32,7 @@ pub const Class = struct {
close_brace_loc: logger.Loc = logger.Loc.Empty,
properties: []Property = &([_]Property{}),
has_decorators: bool = false,
should_lower_standard_decorators: bool = false,

pub fn canBeMoved(this: *const Class) bool {
if (this.extends != null)
Expand Down Expand Up @@ -134,6 +135,7 @@ pub const Property = struct {
declare,
abstract,
class_static_block,
auto_accessor,

pub fn jsonStringify(self: @This(), writer: anytype) !void {
return try writer.write(@tagName(self));
Expand Down
21 changes: 19 additions & 2 deletions src/ast/P.zig
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Original file line number Diff line number Diff line change
Expand Up @@ -99,6 +99,7 @@ pub fn NewParser_(
pub const parseStmtsUpTo = parse_zig.parseStmtsUpTo;
pub const parseAsyncPrefixExpr = parse_zig.parseAsyncPrefixExpr;
pub const parseTypeScriptDecorators = parse_zig.parseTypeScriptDecorators;
pub const parseStandardDecorator = parse_zig.parseStandardDecorator;
pub const parseTypeScriptNamespaceStmt = parse_zig.parseTypeScriptNamespaceStmt;
pub const parseTypeScriptImportEqualsStmt = parse_zig.parseTypeScriptImportEqualsStmt;
pub const parseTypescriptEnumStmt = parse_zig.parseTypescriptEnumStmt;
Expand Down Expand Up @@ -136,6 +137,10 @@ pub fn NewParser_(
pub const findSymbol = symbols_zig.findSymbol;
pub const findSymbolWithRecordUsage = symbols_zig.findSymbolWithRecordUsage;

const lowerDecorators_zig = @import("./lowerDecorators.zig").LowerDecorators(parser_feature__typescript, parser_feature__jsx, parser_feature__scan_only);
pub const lowerStandardDecoratorsStmt = lowerDecorators_zig.lowerStandardDecoratorsStmt;
pub const lowerStandardDecoratorsExpr = lowerDecorators_zig.lowerStandardDecoratorsExpr;

macro: MacroState = undefined,
allocator: Allocator,
options: Parser.Options,
Expand Down Expand Up @@ -486,6 +491,10 @@ pub fn NewParser_(
/// Used for react refresh, it must be able to insert `const _s = $RefreshSig$();`
nearest_stmt_list: ?*ListManaged(Stmt) = null,

/// Name from assignment context for anonymous decorated class expressions.
/// Set before visitExpr, consumed by lowerStandardDecoratorsImpl.
decorator_class_name: ?[]const u8 = null,

Comment on lines +494 to +497

@coderabbitai coderabbitai Bot Jan 28, 2026

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🧹 Nitpick | 🔵 Trivial

Consider private field prefix if this is internal-only

If decorator_class_name isn’t part of the public parser state API, prefer #decorator_class_name and adjust accessors accordingly.

As per coding guidelines: Use the # prefix for private fields in Zig structs, e.g., struct { #foo: u32 };

🤖 Prompt for AI Agents 
In `@src/ast/P.zig` around lines 494 - 497, The field decorator_class_name is
currently public but intended internal-only; rename it to `#decorator_class_name`
and update any direct references and accessor usage accordingly (e.g.,
reads/writes in visitExpr and lowerStandardDecoratorsImpl) to use the new
private-field name, and adjust any getters/setters or patterns that access it so
they compile with Zig's private field syntax.

const RecentlyVisitedTSNamespace = struct {
expr: Expr.Data = Expr.empty.data,
map: ?*js_ast.TSNamespaceMemberMap = null,
Expand Down Expand Up @@ -3759,7 +3768,10 @@ pub fn NewParser_(
}
},
else => {
Output.panic("Unexpected type in export default", .{});
// Standard decorator lowering can produce non-class
// statements as the export default value; conservatively
// assume they have side effects.
return false;
},
}
},
Expand Down Expand Up @@ -4857,6 +4869,11 @@ pub fn NewParser_(
) []Stmt {
switch (stmtorexpr) {
.stmt => |stmt| {
// Standard decorator lowering path (for both JS and TS files)
if (stmt.data.s_class.class.should_lower_standard_decorators) {
return p.lowerStandardDecoratorsStmt(stmt);
}
Comment on lines +4872 to +4875

@coderabbitai coderabbitai Bot Jan 28, 2026

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🧹 Nitpick | 🔵 Trivial

Please add/verify a regression for export default class with standard decorators.
A crash for this case was reported; ensure this path routes through lowerStandardDecoratorsStmt without panicking.

🤖 Prompt for AI Agents 
In `@src/ast/P.zig` around lines 4872 - 4875, The code path for "export default
class" with standard decorators can panic instead of routing through the
standard decorator lowering; ensure that when a statement is an exported default
class whose should_lower_standard_decorators flag is set, it returns
p.lowerStandardDecoratorsStmt(stmt) (use the existing check of
stmt.data.s_class.class.should_lower_standard_decorators and the
lowerStandardDecoratorsStmt function) and does not take any alternative path
that can panic, and add/verify a regression test that parses/transforms an
`export default class` with at least one standard decorator to confirm the
lowering occurs without panic.


if (comptime !is_typescript_enabled) {
if (!stmt.data.s_class.class.has_decorators) {
var stmts = p.allocator.alloc(Stmt, 1) catch unreachable;
Expand Down Expand Up @@ -5007,7 +5024,7 @@ pub fn NewParser_(
}
}
},
.spread, .declare => {}, // not allowed in a class
.spread, .declare, .auto_accessor => {}, // not allowed in a class (auto_accessor is standard decorators only)
.class_static_block => {}, // not allowed to decorate this
}
}
Expand Down
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