Do not remove static class properties that use this. Closes #1385

terser · May 8, 2023 · 26b70f3 · 26b70f3
1 parent 474fca5
commit 26b70f3
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Showing 4 changed files with 79 additions and 13 deletions.
diff --git a/lib/compress/drop-side-effect-free.js b/lib/compress/drop-side-effect-free.js
@@ -165,6 +165,15 @@ def_drop_side_effect_free(AST_Class, function (compressor) {
             }
         }
 
+        if (
+            prop instanceof AST_ClassProperty
+            && prop.static
+            && prop.value.has_side_effects(compressor)
+            && prop.contains_this()
+        ) {
+            return this;
+        }
+
         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
@@ -3358,19 +3358,6 @@ def_optimize(AST_Chain, function (self, compressor) {
     return self;
 });
 
-AST_Lambda.DEFMETHOD("contains_this", function() {
-    return walk(this, node => {
-        if (node instanceof AST_This) return walk_abort;
-        if (
-            node !== this
-            && node instanceof AST_Scope
-            && !(node instanceof AST_Arrow)
-        ) {
-            return true;
-        }
-    });
-});
-
 def_optimize(AST_Dot, function(self, compressor) {
     const parent = compressor.parent();
     if (is_lhs(self, parent)) return self;

diff --git a/lib/compress/inference.js b/lib/compress/inference.js
@@ -84,6 +84,7 @@ import {
   AST_PropAccess,
   AST_RegExp,
   AST_Return,
+  AST_Scope,
   AST_Sequence,
   AST_SimpleStatement,
   AST_Statement,
@@ -950,6 +951,19 @@ export const aborts = (thing) => thing && thing.aborts();
     node.DEFMETHOD("aborts", func);
 });
 
+AST_Node.DEFMETHOD("contains_this", function() {
+    return walk(this, node => {
+        if (node instanceof AST_This) return walk_abort;
+        if (
+            node !== this
+            && node instanceof AST_Scope
+            && !(node instanceof AST_Arrow)
+        ) {
+            return true;
+        }
+    });
+});
+
 export function is_modified(compressor, tw, node, value, level, immutable) {
     var parent = tw.parent(level);
     var lhs = is_lhs(node, parent);

diff --git a/test/compress/drop-unused.js b/test/compress/drop-unused.js
@@ -2774,6 +2774,62 @@ unused_class_with_static_props_side_effects: {
     expect_stdout: "PASS"
 }
 
+unused_class_with_static_props_this: {
+    node_version = ">=12"
+    options = {
+        toplevel: true,
+        unused: true
+    }
+    input: {
+        let _classThis;
+        var Foo = class {
+            static _ = Foo = _classThis = this;
+        };
+        const x = Foo = _classThis;
+        leak(x);
+    }
+    expect: {
+        let _classThis;
+        (class {
+            static _ = _classThis = this;
+        });
+        const x = _classThis;
+        leak(x);
+    }
+}
+
+unused_class_with_static_props_this_2: {
+    node_version = ">=12"
+    options = {
+        toplevel: true,
+        unused: true,
+    }
+    input: {
+        let Foo = (()=>{
+            let _classThis;
+            var Foo = class {
+                static _ = (()=>{
+                    Foo = _classThis = this;
+                })();
+                foo(){
+                    return "PASS";
+                }
+            };
+            return Foo = _classThis;
+        })();
+        console.log(new Foo().foo());
+    }
+    expect: {
+        let Foo = (()=>{
+            let _classThis;
+            (class{static _=(()=>{_classThis=this})();foo(){return "PASS"}});
+            return _classThis
+        })();
+        console.log((new Foo).foo());
+    }
+    expect_stdout: "PASS"
+}
+
 unused_class_with_static_props_side_effects_2: {
     node_version = ">=12"
     options = {