Use custom object formatters for any part of a diff, not just leaf nodes

src/core/matchers/MismatchTree.js

@@ -0,0 +1,62 @@
+getJasmineRequireObj().MismatchTree = function (j$) {
+
+  /*
+    To be able to apply custom object formatters at all possible levels of an
+    object graph, DiffBuilder needs to be able to know not just where the
+    mismatch occurred but also all ancestors of the mismatched value in both
+    the expected and actual object graphs. MismatchTree maintains that context
+    and provides it via the traverse method.
+   */
+  function MismatchTree(path) {
+    this.path = path || new j$.ObjectPath([]);
+    this.formatter = undefined;
+    this.children = [];
+    this.isMismatch = false;
+  }
+
+  MismatchTree.prototype.add = function (path, formatter) {
+    var key, child;
+
+    if (path.depth() === 0) {
+      this.formatter = formatter;
+      this.isMismatch = true;
+    } else {
+      key = path.components[0];
+      path = path.shift();
+      child = this.child(key);
+
+      if (!child) {
+        child = new MismatchTree(this.path.add(key));
+        this.children.push(child);
+      }
+
+      child.add(path, formatter);
+    }
+  };
+
+  MismatchTree.prototype.traverse = function (visit) {
+    var i, hasChildren = this.children.length > 0;
+
+    if (this.isMismatch || hasChildren) {
+      if (visit(this.path, !hasChildren, this.formatter)) {
+        for (i = 0; i < this.children.length; i++) {
+          this.children[i].traverse(visit);
+        }
+      }
+    }
+  };
+
+  MismatchTree.prototype.child = function(key) {
+    var i, pathEls;
+
+    for (i = 0; i < this.children.length; i++) {
+      pathEls = this.children[i].path.components;
+      if (pathEls[pathEls.length - 1] === key) {
+        return this.children[i];
+      }
+    }
+  };
+
+  return MismatchTree;
+};
+