implement `annotations` (#4763)

1 files changed, 25 insertions, 6 deletions

diff --git a/lib/output.js b/lib/output.js
index ff05356e..fc71a62b 100644
--- a/lib/output.js
+++ b/lib/output.js
@@ -52,6 +52,7 @@ function OutputStream(options) {
 
     var readonly = !options;
     options = defaults(options, {
+        annotations      : false,
         ascii_only       : false,
         beautify         : false,
         braces           : false,
@@ -500,12 +501,14 @@ function OutputStream(options) {
                     space();
                 }
             }
+            var value = c.value.replace(/[@#]__PURE__/g, " ");
+            if (/^\s*$/.test(value)) return;
             if (/comment[134]/.test(c.type)) {
-                print("//" + c.value.replace(/[@#]__PURE__/g, " ") + "\n");
+                print("//" + value + "\n");
                 indent();
                 last_nlb = true;
             } else if (c.type == "comment2") {
-                print("/*" + c.value.replace(/[@#]__PURE__/g, " ") + "*/");
+                print("/*" + value + "*/");
                 last_nlb = false;
             }
         });
@@ -558,11 +561,13 @@ function OutputStream(options) {
             } else if (i > 0 || !tail) {
                 space();
             }
+            var value = c.value.replace(/[@#]__PURE__/g, " ");
+            if (/^\s*$/.test(value)) return;
             if (/comment[134]/.test(c.type)) {
-                print("//" + c.value.replace(/[@#]__PURE__/g, " "));
+                print("//" + value);
                 need_newline_indented = true;
             } else if (c.type == "comment2") {
-                print("/*" + c.value.replace(/[@#]__PURE__/g, " ") + "*/");
+                print("/*" + value + "*/");
                 need_space = true;
             }
         });
@@ -1436,6 +1441,17 @@ function OutputStream(options) {
     });
 
     /* -----[ other expressions ]----- */
+    function print_annotation(self, output) {
+        if (!output.option("annotations")) return;
+        if (!self.pure) return;
+        var level = 0, parent = self, node;
+        do {
+            node = parent;
+            parent = output.parent(level++);
+            if (parent instanceof AST_Call && parent.expression === node) return;
+        } while (parent instanceof AST_PropAccess && parent.expression === node);
+        output.print("/*" + self.pure + "*/");
+    }
     function print_call_args(self, output) {
         if (self.expression instanceof AST_Call || self.expression instanceof AST_Lambda) {
             output.add_mapping(self.start);
@@ -1448,11 +1464,14 @@ function OutputStream(options) {
         });
     }
     DEFPRINT(AST_Call, function(output) {
-        this.expression.print(output);
-        print_call_args(this, output);
+        var self = this;
+        print_annotation(self, output);
+        self.expression.print(output);
+        print_call_args(self, output);
     });
     DEFPRINT(AST_New, function(output) {
         var self = this;
+        print_annotation(self, output);
         output.print("new");
         output.space();
         self.expression.print(output);