#873 Fix `conditionals` optimizations with default compress options

2 files changed, 253 insertions, 17 deletions

diff --git a/lib/compress.js b/lib/compress.js
index 32833ebf..44e19799 100644
--- a/lib/compress.js
+++ b/lib/compress.js
@@ -726,6 +726,32 @@ merge(Compressor.prototype, {
                 return [ this ];
             }
         });
+        AST_Node.DEFMETHOD("is_constant", function(compressor){
+            // Accomodate when compress option evaluate=false
+            // as well as the common constant expressions !0 and !1
+            return this instanceof AST_Constant
+                || (this instanceof AST_UnaryPrefix && this.operator == "!"
+                    && this.expression instanceof AST_Constant)
+                || this.evaluate(compressor).length > 1;
+        });
+        // Obtain the constant value of an expression already known to be constant.
+        // Result only valid iff this.is_constant(compressor) is true.
+        AST_Node.DEFMETHOD("constant_value", function(compressor){
+            // Accomodate when option evaluate=false.
+            if (this instanceof AST_Constant) return this.value;
+            // Accomodate the common constant expressions !0 and !1 when option evaluate=false.
+            if (this instanceof AST_UnaryPrefix
+                && this.operator == "!"
+                && this.expression instanceof AST_Constant) {
+                return !this.expression.value;
+            }
+            var result = this.evaluate(compressor)
+            if (result.length > 1) {
+                return result[1];
+            }
+            // should never be reached
+            return undefined;
+        });
         def(AST_Statement, function(){
             throw new Error(string_template("Cannot evaluate a statement [{file}:{line},{col}]", this.start));
         });
@@ -2427,32 +2453,48 @@ merge(Compressor.prototype, {
                 alternative: alternative
             });
         }
-        // x=y?1:1 --> x=1
-        if (consequent instanceof AST_Constant
-            && alternative instanceof AST_Constant
+        // y?1:1 --> 1
+        if (consequent.is_constant(compressor)
+            && alternative.is_constant(compressor)
             && consequent.equivalent_to(alternative)) {
+            var consequent_value = consequent.constant_value();
             if (self.condition.has_side_effects(compressor)) {
-                return AST_Seq.from_array([self.condition, make_node_from_constant(compressor, consequent.value, self)]);
+                return AST_Seq.from_array([self.condition, make_node_from_constant(compressor, consequent_value, self)]);
             } else {
-                return make_node_from_constant(compressor, consequent.value, self);
-
+                return make_node_from_constant(compressor, consequent_value, self);
             }
         }
-        // x=y?true:false --> x=!!y
-        if (consequent instanceof AST_True
-            && alternative instanceof AST_False) {
+
+        // y?true:false --> !!y
+        if (is_true(consequent) && is_false(alternative)) {
             self.condition = self.condition.negate(compressor);
             return make_node(AST_UnaryPrefix, self.condition, {
                 operator: "!",
                 expression: self.condition
             });
         }
-        // x=y?false:true --> x=!y
-        if (consequent instanceof AST_False
-            && alternative instanceof AST_True) {
+        // y?false:true --> !y
+        if (is_false(consequent) && is_true(alternative)) {
             return self.condition.negate(compressor)
         }
         return self;
+
+        // AST_True or !0
+        function is_true(node) {
+            return node instanceof AST_True
+                || (node instanceof AST_UnaryPrefix
+                    && node.operator == "!"
+                    && node.expression instanceof AST_Constant
+                    && !node.expression.value);
+        }
+        // AST_False or !1
+        function is_false(node) {
+            return node instanceof AST_False
+                || (node instanceof AST_UnaryPrefix
+                    && node.operator == "!"
+                    && node.expression instanceof AST_Constant
+                    && !!node.expression.value);
+        }
     });
 
     OPT(AST_Boolean, function(self, compressor){
diff --git a/test/compress/conditionals.js b/test/compress/conditionals.js
index 16ef6d66..65cfea64 100644
--- a/test/compress/conditionals.js
+++ b/test/compress/conditionals.js
@@ -332,53 +332,247 @@ cond_7_1: {
 cond_8: {
     options = {
         conditionals: true,
-        evaluate    : true
+        evaluate    : true,
+        booleans    : false
     };
     input: {
         var a;
         // compress these
         a = condition ? true : false;
-
         a = !condition ? true : false;
-
         a = condition() ? true : false;
 
+        a = condition ? !0 : !1;
+        a = !condition ? !null : !2;
+        a = condition() ? !0 : !-3.5;
+
         if (condition) {
             a = true;
         } else {
             a = false;
         }
 
-        a = condition ? false : true;
+        if (condition) {
+            a = !0;
+        } else {
+            a = !1;
+        }
 
+        a = condition ? false : true;
         a = !condition ? false : true;
-
         a = condition() ? false : true;
 
+        a = condition ? !3 : !0;
+        a = !condition ? !2 : !0;
+        a = condition() ? !1 : !0;
+
         if (condition) {
             a = false;
         } else {
             a = true;
         }
 
+        if (condition) {
+            a = !1;
+        } else {
+            a = !0;
+        }
+
         // don't compress these
         a = condition ? 1 : false;
+        a = !condition ? true : 0;
+        a = condition ? 1 : 0;
+    }
+    expect: {
+        var a;
+        a = !!condition;
+        a = !condition;
+        a = !!condition();
+
+        a = !!condition;
+        a = !condition;
+        a = !!condition();
+
+        a = !!condition;
+        a = !!condition;
+
+        a = !condition;
+        a = !!condition;
+        a = !condition();
+
+        a = !condition;
+        a = !!condition;
+        a = !condition();
+
+        a = !condition;
+        a = !condition;
+
+        a = condition ? 1 : false;
+        a = condition ? 0 : true;
+        a = condition ? 1 : 0;
+    }
+}
 
+cond_8b: {
+    options = {
+        conditionals: true,
+        evaluate    : true,
+        booleans    : true
+    };
+    input: {
+        var a;
+        // compress these
+        a = condition ? true : false;
+        a = !condition ? true : false;
+        a = condition() ? true : false;
+
+        a = condition ? !0 : !1;
+        a = !condition ? !null : !2;
+        a = condition() ? !0 : !-3.5;
+
+        if (condition) {
+            a = true;
+        } else {
+            a = false;
+        }
+
+        if (condition) {
+            a = !0;
+        } else {
+            a = !1;
+        }
+
+        a = condition ? false : true;
+        a = !condition ? false : true;
+        a = condition() ? false : true;
+
+        a = condition ? !3 : !0;
+        a = !condition ? !2 : !0;
+        a = condition() ? !1 : !0;
+
+        if (condition) {
+            a = false;
+        } else {
+            a = true;
+        }
+
+        if (condition) {
+            a = !1;
+        } else {
+            a = !0;
+        }
+
+        a = condition ? 1 : false;
         a = !condition ? true : 0;
+        a = condition ? 1 : 0;
+    }
+    expect: {
+        var a;
+        a = !!condition;
+        a = !condition;
+        a = !!condition();
 
+        a = !!condition;
+        a = !condition;
+        a = !!condition();
+
+        a = !!condition;
+        a = !!condition;
+
+        a = !condition;
+        a = !!condition;
+        a = !condition();
+
+        a = !condition;
+        a = !!condition;
+        a = !condition();
+
+        a = !condition;
+        a = !condition;
+
+        a = condition ? 1 : !1;
+        a = condition ? 0 : !0;
         a = condition ? 1 : 0;
+    }
+}
+
+cond_8c: {
+    options = {
+        conditionals: true,
+        evaluate    : false,
+        booleans    : false
+    };
+    input: {
+        var a;
+        // compress these
+        a = condition ? true : false;
+        a = !condition ? true : false;
+        a = condition() ? true : false;
 
+        a = condition ? !0 : !1;
+        a = !condition ? !null : !2;
+        a = condition() ? !0 : !-3.5;
+
+        if (condition) {
+            a = true;
+        } else {
+            a = false;
+        }
+
+        if (condition) {
+            a = !0;
+        } else {
+            a = !1;
+        }
+
+        a = condition ? false : true;
+        a = !condition ? false : true;
+        a = condition() ? false : true;
+
+        a = condition ? !3 : !0;
+        a = !condition ? !2 : !0;
+        a = condition() ? !1 : !0;
+
+        if (condition) {
+            a = false;
+        } else {
+            a = true;
+        }
+
+        if (condition) {
+            a = !1;
+        } else {
+            a = !0;
+        }
+
+        a = condition ? 1 : false;
+        a = !condition ? true : 0;
+        a = condition ? 1 : 0;
     }
     expect: {
         var a;
         a = !!condition;
         a = !condition;
         a = !!condition();
+
+        a = !!condition;
+        a = !condition;
+        a = condition() ? !0 : !-3.5;
+
+        a = !!condition;
+        a = !!condition;
+
+        a = !condition;
         a = !!condition;
+        a = !condition();
+
         a = !condition;
         a = !!condition;
         a = !condition();
+
         a = !condition;
+        a = !condition;
+
         a = condition ? 1 : false;
         a = condition ? 0 : true;
         a = condition ? 1 : 0;