SERVER-23371 Add initializer_list constructor for Documents.

4 files changed, 57 insertions, 27 deletions

diff --git a/src/mongo/db/pipeline/document.cpp b/src/mongo/db/pipeline/document.cpp
index 6b2cf793aba..f7c8b179094 100644
--- a/src/mongo/db/pipeline/document.cpp
+++ b/src/mongo/db/pipeline/document.cpp
@@ -227,6 +227,16 @@ Document::Document(const BSONObj& bson) {
     *this = md.freeze();
 }
 
+Document::Document(std::initializer_list<std::pair<StringData, ImplicitValue>> initializerList) {
+    MutableDocument mutableDoc(initializerList.size());
+
+    for (auto&& pair : initializerList) {
+        mutableDoc.addField(pair.first, pair.second);
+    }
+
+    *this = mutableDoc.freeze();
+}
+
 BSONObjBuilder& operator<<(BSONObjBuilderValueStream& builder, const Document& doc) {
     BSONObjBuilder subobj(builder.subobjStart());
     doc.toBson(&subobj);
diff --git a/src/mongo/db/pipeline/document.h b/src/mongo/db/pipeline/document.h
index 9b2857a011d..c0bf581110e 100644
--- a/src/mongo/db/pipeline/document.h
+++ b/src/mongo/db/pipeline/document.h
@@ -72,6 +72,13 @@ public:
     /// Create a new Document deep-converted from the given BSONObj.
     explicit Document(const BSONObj& bson);
 
+    /**
+     * Create a new document from key, value pairs. Enables constructing a document using this
+     * syntax:
+     * auto document = Document{{"hello", "world"}, {"number": 1}};
+     */
+    Document(std::initializer_list<std::pair<StringData, ImplicitValue>> initializerList);
+
 #if defined(_MSC_VER) && _MSC_VER < 1900  // MVSC++ <= 2013 can't generate default move operations
     Document(const Document& other) = default;
     Document& operator=(const Document& other) = default;
diff --git a/src/mongo/db/pipeline/document_value_test.cpp b/src/mongo/db/pipeline/document_value_test.cpp
index d77c7ac0039..9a8089248c2 100644
--- a/src/mongo/db/pipeline/document_value_test.cpp
+++ b/src/mongo/db/pipeline/document_value_test.cpp
@@ -70,32 +70,36 @@ void assertRoundTrips(const Document& document1) {
     ASSERT_EQUALS(document1, document2);
 }
 
-/** Create a Document. */
-class Create {
-public:
-    void run() {
-        Document document;
-        ASSERT_EQUALS(0U, document.size());
-        assertRoundTrips(document);
-    }
-};
+TEST(DocumentConstruction, Default) {
+    Document document;
+    ASSERT_EQUALS(0U, document.size());
+    assertRoundTrips(document);
+}
 
-/** Create a Document from a BSONObj. */
-class CreateFromBsonObj {
-public:
-    void run() {
-        Document document = fromBson(BSONObj());
-        ASSERT_EQUALS(0U, document.size());
-        document = fromBson(BSON("a" << 1 << "b"
-                                     << "q"));
-        ASSERT_EQUALS(2U, document.size());
-        ASSERT_EQUALS("a", getNthField(document, 0).first.toString());
-        ASSERT_EQUALS(1, getNthField(document, 0).second.getInt());
-        ASSERT_EQUALS("b", getNthField(document, 1).first.toString());
-        ASSERT_EQUALS("q", getNthField(document, 1).second.getString());
-        assertRoundTrips(document);
-    }
-};
+TEST(DocumentConstruction, FromEmptyBson) {
+    Document document = fromBson(BSONObj());
+    ASSERT_EQUALS(0U, document.size());
+    assertRoundTrips(document);
+}
+
+TEST(DocumentConstruction, FromNonEmptyBson) {
+    Document document = fromBson(BSON("a" << 1 << "b"
+                                          << "q"));
+    ASSERT_EQUALS(2U, document.size());
+    ASSERT_EQUALS("a", getNthField(document, 0).first.toString());
+    ASSERT_EQUALS(1, getNthField(document, 0).second.getInt());
+    ASSERT_EQUALS("b", getNthField(document, 1).first.toString());
+    ASSERT_EQUALS("q", getNthField(document, 1).second.getString());
+}
+
+TEST(DocumentConstruction, FromInitializerList) {
+    auto document = Document{{"a", 1}, {"b", "q"}};
+    ASSERT_EQUALS(2U, document.size());
+    ASSERT_EQUALS("a", getNthField(document, 0).first.toString());
+    ASSERT_EQUALS(1, getNthField(document, 0).second.getInt());
+    ASSERT_EQUALS("b", getNthField(document, 1).first.toString());
+    ASSERT_EQUALS("q", getNthField(document, 1).second.getString());
+}
 
 /** Add Document fields. */
 class AddField {
@@ -1669,8 +1673,6 @@ class All : public Suite {
 public:
     All() : Suite("document") {}
     void setupTests() {
-        add<Document::Create>();
-        add<Document::CreateFromBsonObj>();
         add<Document::AddField>();
         add<Document::GetValue>();
         add<Document::SetField>();
diff --git a/src/mongo/db/pipeline/value.h b/src/mongo/db/pipeline/value.h
index 9fc51e164b2..920b5910204 100644
--- a/src/mongo/db/pipeline/value.h
+++ b/src/mongo/db/pipeline/value.h
@@ -305,6 +305,17 @@ typedef unordered_set<Value, Value::Hash> ValueSet;
 inline void swap(mongo::Value& lhs, mongo::Value& rhs) {
     lhs.swap(rhs);
 }
+
+/**
+ * This class is identical to Value, but supports implicit creation from any of the types explicitly
+ * supported by Value.
+ */
+class ImplicitValue : public Value {
+public:
+    template <typename T>
+    ImplicitValue(T arg)
+        : Value(std::move(arg)) {}
+};
 }
 
 /* ======================= INLINED IMPLEMENTATIONS ========================== */