enhance `properties` (#2412)

- trim array items only if `side_effects`
- extend to non-identifier properties

1 files changed, 86 insertions, 65 deletions

diff --git a/lib/compress.js b/lib/compress.js
index 4817ec5f..a1db985c 100644
--- a/lib/compress.js
+++ b/lib/compress.js
@@ -4537,59 +4537,72 @@ merge(Compressor.prototype, {
     });
 
     OPT(AST_Sub, function(self, compressor){
+        var expr = self.expression;
+        var prop = self.property;
         if (compressor.option("properties")) {
-            var prop = self.property;
-            if (prop instanceof AST_String) {
-                prop = prop.getValue();
-                if (is_identifier_string(prop)) {
+            var key = prop.evaluate(compressor);
+            if (key !== prop) {
+                var property = "" + key;
+                if (is_identifier_string(property)
+                    && property.length <= prop.print_to_string().length + 1) {
                     return make_node(AST_Dot, self, {
-                        expression : self.expression,
-                        property   : prop
+                        expression: expr,
+                        property: property
                     }).optimize(compressor);
                 }
-                var v = parseFloat(prop);
-                if (!isNaN(v) && v.toString() == prop) {
-                    self.property = make_node(AST_Number, self.property, {
-                        value: v
-                    });
+                if (!(prop instanceof AST_Number)) {
+                    var value = parseFloat(property);
+                    if (value.toString() == property) {
+                        prop = self.property = make_node(AST_Number, prop, {
+                            value: value
+                        });
+                    }
                 }
             }
-            if (prop instanceof AST_Number && self.expression instanceof AST_Array) {
-                prop = prop.getValue();
-                var elements = self.expression.elements;
-                if (prop in elements) {
-                    var flatten = true;
-                    var values = [];
-                    for (var i = elements.length; --i > prop;) {
-                        var value = elements[i].drop_side_effect_free(compressor);
-                        if (value) {
-                            values.unshift(value);
-                            if (flatten && value.has_side_effects(compressor)) flatten = false;
-                        }
-                    }
-                    var retValue = elements[prop];
-                    retValue = retValue instanceof AST_Hole ? make_node(AST_Undefined, retValue) : retValue;
-                    if (!flatten) values.unshift(retValue);
-                    while (--i >= 0) {
-                        var value = elements[i].drop_side_effect_free(compressor);
-                        if (value) values.unshift(value);
-                        else prop--;
+        }
+        if (is_lhs(self, compressor.parent())) return self;
+        if (compressor.option("properties") && key !== prop) {
+            var node = self.flatten_object(property);
+            if (node) {
+                expr = self.expression = node.expression;
+                prop = self.property = node.property;
+            }
+        }
+        if (compressor.option("properties") && compressor.option("side_effects")
+            && prop instanceof AST_Number && expr instanceof AST_Array) {
+            var index = prop.getValue();
+            var elements = expr.elements;
+            if (index in elements) {
+                var flatten = true;
+                var values = [];
+                for (var i = elements.length; --i > index;) {
+                    var value = elements[i].drop_side_effect_free(compressor);
+                    if (value) {
+                        values.unshift(value);
+                        if (flatten && value.has_side_effects(compressor)) flatten = false;
                     }
-                    if (flatten) {
-                        values.push(retValue);
-                        return make_sequence(self, values).optimize(compressor);
-                    } else return make_node(AST_Sub, self, {
-                        expression: make_node(AST_Array, self.expression, {
-                            elements: values
-                        }),
-                        property: make_node(AST_Number, self.property, {
-                            value: prop
-                        })
-                    });
                 }
+                var retValue = elements[index];
+                retValue = retValue instanceof AST_Hole ? make_node(AST_Undefined, retValue) : retValue;
+                if (!flatten) values.unshift(retValue);
+                while (--i >= 0) {
+                    var value = elements[i].drop_side_effect_free(compressor);
+                    if (value) values.unshift(value);
+                    else index--;
+                }
+                if (flatten) {
+                    values.push(retValue);
+                    return make_sequence(self, values).optimize(compressor);
+                } else return make_node(AST_Sub, self, {
+                    expression: make_node(AST_Array, expr, {
+                        elements: values
+                    }),
+                    property: make_node(AST_Number, prop, {
+                        value: index
+                    })
+                });
             }
         }
-        if (is_lhs(self, compressor.parent())) return self;
         var ev = self.evaluate(compressor);
         if (ev !== self) {
             ev = make_node_from_constant(ev, self).optimize(compressor);
@@ -4609,6 +4622,33 @@ merge(Compressor.prototype, {
         return result;
     });
 
+    AST_PropAccess.DEFMETHOD("flatten_object", function(key) {
+        var expr = this.expression;
+        if (expr instanceof AST_Object) {
+            var props = expr.properties;
+            for (var i = props.length; --i >= 0;) {
+                var prop = props[i];
+                if ("" + prop.key == key) {
+                    if (!all(props, function(prop) {
+                        return prop instanceof AST_ObjectKeyVal;
+                    })) break;
+                    var value = prop.value;
+                    if (value instanceof AST_Function && value.contains_this()) break;
+                    return make_node(AST_Sub, this, {
+                        expression: make_node(AST_Array, expr, {
+                            elements: props.map(function(prop) {
+                                return prop.value;
+                            })
+                        }),
+                        property: make_node(AST_Number, this, {
+                            value: i
+                        })
+                    });
+                }
+            }
+        }
+    });
+
     OPT(AST_Dot, function(self, compressor){
         var def = self.resolve_defines(compressor);
         if (def) {
@@ -4637,28 +4677,9 @@ merge(Compressor.prototype, {
             }
         }
         if (is_lhs(self, compressor.parent())) return self;
-        if (compressor.option("properties") && self.expression instanceof AST_Object) {
-            var props = self.expression.properties;
-            for (var i = props.length; --i >= 0;) {
-                var prop = props[i];
-                if (prop.key === self.property) {
-                    if (!all(props, function(prop) {
-                        return prop instanceof AST_ObjectKeyVal;
-                    })) break;
-                    var value = prop.value;
-                    if (value instanceof AST_Function && value.contains_this()) break;
-                    return make_node(AST_Sub, self, {
-                        expression: make_node(AST_Array, self.expression, {
-                            elements: props.map(function(prop) {
-                                return prop.value;
-                            })
-                        }),
-                        property: make_node(AST_Number, self, {
-                            value: i
-                        })
-                    }).optimize(compressor);
-                }
-            }
+        if (compressor.option("properties")) {
+            var node = self.flatten_object(self.property);
+            if (node) return node.optimize(compressor);
         }
         var ev = self.evaluate(compressor);
         if (ev !== self) {