basic support for class static blocks. Closes #1093

terser · Aug 20, 2022 · c677e28 · c677e28
1 parent 5ca7d86
commit c677e28
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Showing 12 changed files with 248 additions and 13 deletions.
diff --git a/lib/ast.js b/lib/ast.js
@@ -2272,6 +2272,28 @@ var AST_DefClass = DEFNODE("DefClass", null, function AST_DefClass(props) {
     $documentation: "A class definition",
 }, AST_Class);
 
+var AST_ClassStaticBlock = DEFNODE("ClassStaticBlock", "body block_scope", function AST_ClassStaticBlock (props) {
+    this.body = props.body;
+    this.block_scope = props.block_scope;
+    this.start = props.start;
+    this.end = props.end;
+}, {
+    $documentation: "A block containing statements to be executed in the context of the class",
+    $propdoc: {
+        body: "[AST_Statement*] an array of statements",
+    },
+    _walk: function(visitor) {
+        return visitor._visit(this, function() {
+            walk_body(this, visitor);
+        });
+    },
+    _children_backwards(push) {
+        let i = this.body.length;
+        while (i--) push(this.body[i]);
+    },
+    clone: clone_block_scope,
+}, AST_Scope);
+
 var AST_ClassExpression = DEFNODE("ClassExpression", null, function AST_ClassExpression(props) {
     if (props) {
         this.name = props.name;
@@ -3072,6 +3094,7 @@ export {
     AST_ClassExpression,
     AST_ClassPrivateProperty,
     AST_ClassProperty,
+    AST_ClassStaticBlock,
     AST_ConciseMethod,
     AST_Conditional,
     AST_Const,

diff --git a/lib/cli.js b/lib/cli.js
@@ -279,7 +279,9 @@ export async function run_cli({ program, packageJson, fs, path }) {
                         result.enclosed = value.block_scope.enclosed;
                     }
                     value.CTOR.PROPS.forEach(function(prop) {
-                        result[prop] = value[prop];
+                        if (prop !== "block_scope") {
+                            result[prop] = value[prop];
+                        }
                     });
                     return result;
                 }

diff --git a/lib/compress/drop-side-effect-free.js b/lib/compress/drop-side-effect-free.js
@@ -50,6 +50,7 @@ import {
     AST_Call,
     AST_Chain,
     AST_Class,
+    AST_ClassStaticBlock,
     AST_ClassProperty,
     AST_ConciseMethod,
     AST_Conditional,
@@ -156,6 +157,14 @@ def_drop_side_effect_free(AST_Class, function (compressor) {
     if (trimmed_extends)
         with_effects.push(trimmed_extends);
     for (const prop of this.properties) {
+        if (prop instanceof AST_ClassStaticBlock) {
+            if (prop.body.some(stat => stat.has_side_effects(compressor))) {
+                return this;
+            } else {
+                continue;
+            }
+        }
+
         const trimmed_prop = prop.drop_side_effect_free(compressor);
         if (trimmed_prop)
             with_effects.push(trimmed_prop);

diff --git a/lib/compress/index.js b/lib/compress/index.js
@@ -58,6 +58,7 @@ import {
     AST_Class,
     AST_ClassExpression,
     AST_ClassProperty,
+    AST_ClassStaticBlock,
     AST_ConciseMethod,
     AST_Conditional,
     AST_Const,
@@ -833,18 +834,13 @@ AST_Scope.DEFMETHOD("drop_unused", function(compressor) {
             }
             if ((node instanceof AST_Defun || node instanceof AST_DefClass) && node !== self) {
                 const def = node.name.definition();
-                let keep = def.global && !drop_funcs || in_use_ids.has(def.id);
-                if (!keep) {
+                const keep = def.global && !drop_funcs || in_use_ids.has(def.id);
+                // Class "extends" and static blocks may have side effects
+                const has_side_effects = !keep
+                    && node instanceof AST_Class
+                    && node.has_side_effects(compressor);
+                if (!keep && !has_side_effects) {
                     def.eliminated++;
-                    if (node instanceof AST_DefClass) {
-                        // Classes might have extends with side effects
-                        const side_effects = node.drop_side_effect_free(compressor);
-                        if (side_effects) {
-                            return make_node(AST_SimpleStatement, node, {
-                                body: side_effects
-                            });
-                        }
-                    }
                     return in_list ? MAP.skip : make_node(AST_EmptyStatement, node);
                 }
             }
@@ -3923,6 +3919,11 @@ def_optimize(AST_Class, function(self) {
     return self;
 });
 
+def_optimize(AST_ClassStaticBlock, function(self, compressor) {
+    tighten_body(self.body, compressor);
+    return self;
+});
+
 def_optimize(AST_Yield, function(self, compressor) {
     if (self.expression && !self.is_star && is_undefined(self.expression, compressor)) {
         self.expression = null;

diff --git a/lib/compress/inference.js b/lib/compress/inference.js
@@ -52,6 +52,8 @@ import {
   AST_Case,
   AST_Chain,
   AST_Class,
+  AST_DefClass,
+  AST_ClassStaticBlock,
   AST_ClassProperty,
   AST_ConciseMethod,
   AST_Conditional,
@@ -320,6 +322,9 @@ export function is_nullish(node, compressor) {
         }
         return any(this.properties, compressor);
     });
+    def_has_side_effects(AST_ClassStaticBlock, function(compressor) {
+        return any(this.body, compressor);
+    });
     def_has_side_effects(AST_Binary, function(compressor) {
         return this.left.has_side_effects(compressor)
             || this.right.has_side_effects(compressor);
@@ -419,6 +424,9 @@ export function is_nullish(node, compressor) {
         if (this.extends && this.extends.may_throw(compressor)) return true;
         return any(this.properties, compressor);
     });
+    def_may_throw(AST_ClassStaticBlock, function (compressor) {
+        return any(this.body, compressor);
+    });
 
     def_may_throw(AST_Array, function(compressor) {
         return any(this.elements, compressor);
@@ -587,6 +595,9 @@ export function is_nullish(node, compressor) {
             if (prop.static && prop.value && !prop.value.is_constant_expression(scope)) {
                 return false;
             }
+            if (prop instanceof AST_ClassStaticBlock) {
+                return false;
+            }
         }
 
         return all_refs_local.call(this, scope);
@@ -910,9 +921,18 @@ export const aborts = (thing) => thing && thing.aborts();
         }
         return null;
     }
-    def_aborts(AST_Import, function() { return null; });
+    def_aborts(AST_Import, return_null);
     def_aborts(AST_BlockStatement, block_aborts);
     def_aborts(AST_SwitchBranch, block_aborts);
+    def_aborts(AST_DefClass, function () {
+        for (const prop of this.properties) {
+            if (prop instanceof AST_ClassStaticBlock) {
+                if (prop.aborts()) return prop;
+            }
+        }
+        return null;
+    });
+    def_aborts(AST_ClassStaticBlock, block_aborts);
     def_aborts(AST_If, function() {
         return this.alternative && aborts(this.body) && aborts(this.alternative) && this;
     });

diff --git a/lib/compress/reduce-vars.js b/lib/compress/reduce-vars.js
@@ -52,6 +52,7 @@ import {
     AST_Case,
     AST_Chain,
     AST_Class,
+    AST_ClassStaticBlock,
     AST_ClassExpression,
     AST_Conditional,
     AST_Default,
@@ -377,6 +378,10 @@ def_reduce_vars(AST_Class, function(tw, descend) {
     return true;
 });
 
+def_reduce_vars(AST_ClassStaticBlock, function(tw, descend, compressor) {
+    reset_block_variables(compressor, this);
+});
+
 def_reduce_vars(AST_Conditional, function(tw) {
     this.condition.walk(tw);
     push(tw);

diff --git a/lib/mozilla-ast.js b/lib/mozilla-ast.js
@@ -60,6 +60,7 @@ import {
     AST_Catch,
     AST_Chain,
     AST_Class,
+    AST_ClassStaticBlock,
     AST_ClassExpression,
     AST_ClassProperty,
     AST_ClassPrivateProperty,
@@ -444,6 +445,14 @@ import { is_basic_identifier_string } from "./parse.js";
             });
         },
 
+        StaticBlock: function(M) {
+            return new AST_ClassStaticBlock({
+                start : my_start_token(M),
+                end   : my_end_token(M),
+                body  : M.body.map(from_moz),
+            });
+        },
+
         ArrayExpression: function(M) {
             return new AST_Array({
                 start    : my_start_token(M),
@@ -1583,6 +1592,13 @@ import { is_basic_identifier_string } from "./parse.js";
         };
     });
 
+    def_to_moz(AST_ClassStaticBlock, function To_Moz_StaticBlock(M) {
+        return {
+            type: "StaticBlock",
+            body: M.body.map(to_moz),
+        };
+    });
+
     def_to_moz(AST_NewTarget, function To_Moz_MetaProperty() {
         return {
             type: "MetaProperty",

diff --git a/lib/output.js b/lib/output.js
@@ -70,6 +70,7 @@ import {
     AST_ClassExpression,
     AST_ClassPrivateProperty,
     AST_ClassProperty,
+    AST_ClassStaticBlock,
     AST_ConciseMethod,
     AST_PrivateGetter,
     AST_PrivateMethod,
@@ -2194,6 +2195,11 @@ function OutputStream(options) {
         }
         self._print_getter_setter(type, false, output);
     });
+    DEFPRINT(AST_ClassStaticBlock, function (self, output) {
+        output.print("static");
+        output.space();
+        print_braced(self, output);
+    });
     AST_Symbol.DEFMETHOD("_do_print", function(output) {
         var def = this.definition();
         output.print_name(def ? def.mangled_name || def.name : this.name);

diff --git a/lib/parse.js b/lib/parse.js
@@ -67,6 +67,7 @@ import {
     AST_ClassExpression,
     AST_ClassPrivateProperty,
     AST_ClassProperty,
+    AST_ClassStaticBlock,
     AST_ConciseMethod,
     AST_PrivateGetter,
     AST_PrivateMethod,
@@ -2562,6 +2563,10 @@ function parse($TEXT, options) {
         var accessor_type = null;
 
         if (is_class && name === "static" && is_not_method_start()) {
+            const static_block = class_static_block();
+            if (static_block != null) {
+                return static_block;
+            }
             is_static = true;
             name = as_property_name();
         }
@@ -2668,6 +2673,25 @@ function parse($TEXT, options) {
         }
     }
 
+    function class_static_block() {
+        if (!is("punc", "{")) {
+            return null;
+        }
+
+        const start = S.token;
+        const body = [];
+
+        next();
+
+        while (!is("punc", "}")) {
+            body.push(statement());
+        }
+
+        next();
+
+        return new AST_ClassStaticBlock({ start, body, end: prev() });
+    }
+
     function maybe_import_assertion() {
         if (is("name", "assert") && !has_newline_before(S.token)) {
             next();

diff --git a/lib/size.js b/lib/size.js
@@ -10,6 +10,7 @@ import {
     AST_Call,
     AST_Case,
     AST_Class,
+    AST_ClassStaticBlock,
     AST_ClassPrivateProperty,
     AST_ClassProperty,
     AST_ConciseMethod,
@@ -401,6 +402,11 @@ AST_Class.prototype._size = function () {
     );
 };
 
+AST_ClassStaticBlock.prototype._size = function () {
+    // "class{}" + semicolons
+    return 7 + list_overhead(this.body);
+};
+
 AST_ClassProperty.prototype._size = function () {
     return (
         static_size(this.static)

diff --git a/lib/transform.js b/lib/transform.js
@@ -53,6 +53,7 @@ import {
     AST_Catch,
     AST_Chain,
     AST_Class,
+    AST_ClassStaticBlock,
     AST_Conditional,
     AST_Definitions,
     AST_Destructuring,
@@ -285,6 +286,10 @@ def_transform(AST_Class, function(self, tw) {
     self.properties = do_list(self.properties, tw);
 });
 
+def_transform(AST_ClassStaticBlock, function(self, tw) {
+    self.body = do_list(self.body, tw);
+});
+
 def_transform(AST_Expansion, function(self, tw) {
     self.expression = self.expression.transform(tw);
 });