From 0ae54abdcc289970864d146a33462536da2d73f8 Mon Sep 17 00:00:00 2001
From: John Firebaugh <john.firebaugh@gmail.com>
Date: Sun, 12 May 2013 12:40:00 -0700
Subject: [PATCH] Extract iD.actions.DiscardTags

---
 index.html                        |  1 +
 js/id/actions/discard_tags.js     | 16 ++++++++++++++++
 js/id/core/history.js             | 21 +++++++++------------
 js/id/ui/save.js                  |  2 +-
 test/index.html                   |  2 ++
 test/index_packaged.html          |  1 +
 test/spec/actions/discard_tags.js | 25 +++++++++++++++++++++++++
 7 files changed, 55 insertions(+), 13 deletions(-)
 create mode 100644 js/id/actions/discard_tags.js
 create mode 100644 test/spec/actions/discard_tags.js

diff --git a/index.html b/index.html
index 3b4f714a3..b1c211b11 100644
--- a/index.html
+++ b/index.html
@@ -125,6 +125,7 @@
         <script src='js/id/actions/delete_node.js'></script>
         <script src="js/id/actions/delete_relation.js"></script>
         <script src="js/id/actions/delete_way.js"></script>
+        <script src='js/id/actions/discard_tags.js'></script>
         <script src='js/id/actions/disconnect.js'></script>
         <script src='js/id/actions/join.js'></script>
         <script src='js/id/actions/merge.js'></script>
diff --git a/js/id/actions/discard_tags.js b/js/id/actions/discard_tags.js
new file mode 100644
index 000000000..855db3b13
--- /dev/null
+++ b/js/id/actions/discard_tags.js
@@ -0,0 +1,16 @@
+iD.actions.DiscardTags = function(difference) {
+    return function(graph) {
+        function discardTags(entity) {
+            if (!_.isEmpty(entity.tags)) {
+                graph = graph.replace(entity.update({
+                    tags: _.omit(entity.tags, iD.data.discarded)
+                }));
+            }
+        }
+
+        difference.modified().forEach(discardTags);
+        difference.created().forEach(discardTags);
+
+        return graph;
+    }
+};
diff --git a/js/id/core/history.js b/js/id/core/history.js
index 498b8bb92..7a315a965 100644
--- a/js/id/core/history.js
+++ b/js/id/core/history.js
@@ -137,22 +137,19 @@ iD.History = function(context) {
             return iD.Difference(base, head);
         },
 
-        changes: function() {
-            var difference = history.difference();
+        changes: function(action) {
+            var base = stack[0].graph,
+                head = stack[index].graph;
 
-            function discardTags(entity) {
-                if (_.isEmpty(entity.tags)) {
-                    return entity;
-                } else {
-                    return entity.update({
-                        tags: _.omit(entity.tags, iD.data.discarded)
-                    });
-                }
+            if (action) {
+                head = action(head);
             }
 
+            var difference = iD.Difference(base, head);
+
             return {
-                modified: difference.modified().map(discardTags),
-                created: difference.created().map(discardTags),
+                modified: difference.modified(),
+                created: difference.created(),
                 deleted: difference.deleted()
             };
         },
diff --git a/js/id/ui/save.js b/js/id/ui/save.js
index a6c2df16d..ddcb6a9e6 100644
--- a/js/id/ui/save.js
+++ b/js/id/ui/save.js
@@ -38,7 +38,7 @@ iD.ui.Save = function(context) {
             .call(loading);
 
         connection.putChangeset(
-            history.changes(),
+            history.changes(iD.actions.DiscardTags(history.difference())),
             e.comment,
             history.imagery_used(),
             function(err, changeset_id) {
diff --git a/test/index.html b/test/index.html
index 8fa705b2c..0f1bf2166 100644
--- a/test/index.html
+++ b/test/index.html
@@ -110,6 +110,7 @@
     <script src='../js/id/actions/delete_node.js'></script>
     <script src="../js/id/actions/delete_relation.js"></script>
     <script src="../js/id/actions/delete_way.js"></script>
+    <script src='../js/id/actions/discard_tags.js'></script>
     <script src='../js/id/actions/disconnect.js'></script>
     <script src='../js/id/actions/join.js'></script>
     <script src='../js/id/actions/merge.js'></script>
@@ -191,6 +192,7 @@
     <script src="spec/actions/delete_node.js"></script>
     <script src="spec/actions/delete_relation.js"></script>
     <script src="spec/actions/delete_way.js"></script>
+    <script src='spec/actions/discard_tags.js'></script>
     <script src='spec/actions/disconnect.js'></script>
     <script src="spec/actions/join.js"></script>
     <script src='spec/actions/merge.js'></script>
diff --git a/test/index_packaged.html b/test/index_packaged.html
index 2d7e7c55d..31110349d 100644
--- a/test/index_packaged.html
+++ b/test/index_packaged.html
@@ -34,6 +34,7 @@
     <script src="spec/actions/delete_node.js"></script>
     <script src="spec/actions/delete_relation.js"></script>
     <script src="spec/actions/delete_way.js"></script>
+    <script src='spec/actions/discard_tags.js'></script>
     <script src='spec/actions/disconnect.js'></script>
     <script src="spec/actions/join.js"></script>
     <script src='spec/actions/merge.js'></script>
diff --git a/test/spec/actions/discard_tags.js b/test/spec/actions/discard_tags.js
new file mode 100644
index 000000000..3a5e3f612
--- /dev/null
+++ b/test/spec/actions/discard_tags.js
@@ -0,0 +1,25 @@
+describe("iD.actions.DiscardTags", function() {
+    it("discards obsolete tags from modified entities", function() {
+        var way    = iD.Way({id: 'w1', tags: {created_by: 'Potlatch'}}),
+            base   = iD.Graph([way]),
+            head   = base.replace(way.update({tags: {created_by: 'Potlatch', foo: 'bar'}})),
+            action = iD.actions.DiscardTags(iD.Difference(base, head));
+        expect(action(head).entity(way.id).tags).to.eql({foo: 'bar'});
+    });
+
+    it("discards obsolete tags from created entities", function() {
+        var way    = iD.Way({tags: {created_by: 'Potlatch'}}),
+            base   = iD.Graph(),
+            head   = base.replace(way),
+            action = iD.actions.DiscardTags(iD.Difference(base, head));
+        expect(action(head).entity(way.id).tags).to.eql({});
+    });
+
+    it("doesn't modify entities without obsolete tags", function() {
+        var way    = iD.Way(),
+            base   = iD.Graph(),
+            head   = base.replace(way),
+            action = iD.actions.DiscardTags(iD.Difference(base, head));
+        expect(action(head).entity(way.id)).to.equal(way);
+    });
+});