runtime: changing snapshot access to be const (envoyproxy#7677) (#26)

This is a precursor to envoyproxy#7601 just to land the API change more quickly and make sure it sticks.

Risk Level: Low
Testing: existing unit tests
Docs Changes: n/a
Release Notes: n/a

Signed-off-by: Alyssa Wilk <alyssar@chromium.org>
Signed-off-by: Piotr Sikora <piotrsikora@google.com>

include/envoy/runtime/runtime.h

@@ -220,11 +220,11 @@ class Loader {
  virtual void initialize(Upstream::ClusterManager& cm) PURE;
 
  /**
- * @return Snapshot& the current snapshot. This reference is safe to use for the duration of
+ * @return const Snapshot& the current snapshot. This reference is safe to use for the duration of
  * the calling routine, but may be overwritten on a future event loop cycle so should be
  * fetched again when needed.
  */
- virtual Snapshot& snapshot() PURE;
+ virtual const Snapshot& snapshot() PURE;
 
  /**
  * Merge the given map of key-value pairs into the runtime's state. To remove a previous merge for

source/common/runtime/runtime_impl.cc

@@ -557,7 +557,7 @@ void LoaderImpl::loadNewSnapshot() {
  });
 }
 
-Snapshot& LoaderImpl::snapshot() { return tls_->getTyped<Snapshot>(); }
+const Snapshot& LoaderImpl::snapshot() { return tls_->getTyped<Snapshot>(); }
 
 void LoaderImpl::mergeValues(const std::unordered_map<std::string, std::string>& values) {
  if (admin_layer_ == nullptr) {

source/common/runtime/runtime_impl.h

@@ -243,7 +243,7 @@ class LoaderImpl : public Loader, Logger::Loggable<Logger::Id::runtime> {
 
  // Runtime::Loader
  void initialize(Upstream::ClusterManager& cm) override;
- Snapshot& snapshot() override;
+ const Snapshot& snapshot() override;
  void mergeValues(const std::unordered_map<std::string, std::string>& values) override;
 
 private:

test/common/runtime/runtime_impl_test.cc

@@ -155,7 +155,7 @@ TEST_F(DiskLoaderImplTest, All) {
  EXPECT_EQ(123UL, loader_->snapshot().getInteger("file4", 1));
 
  bool value;
- SnapshotImpl* snapshot = reinterpret_cast<SnapshotImpl*>(&loader_->snapshot());
+ const SnapshotImpl* snapshot = reinterpret_cast<const SnapshotImpl*>(&loader_->snapshot());
 
  // Validate that the layer name is set properly for static layers.
  EXPECT_EQ("base", snapshot->getLayers()[0]->name());
@@ -538,7 +538,7 @@ TEST_F(StaticLoaderImplTest, ProtoParsing) {
 
  // Boolean getting.
  bool value;
- SnapshotImpl* snapshot = reinterpret_cast<SnapshotImpl*>(&loader_->snapshot());
+ const SnapshotImpl* snapshot = reinterpret_cast<const SnapshotImpl*>(&loader_->snapshot());
 
  EXPECT_EQ(true, snapshot->getBoolean("file11", value));
  EXPECT_EQ(true, value);

test/mocks/runtime/mocks.h

@@ -63,7 +63,7 @@ class MockLoader : public Loader {
  ~MockLoader();
 
  MOCK_METHOD1(initialize, void(Upstream::ClusterManager& cm));
- MOCK_METHOD0(snapshot, Snapshot&());
+ MOCK_METHOD0(snapshot, const Snapshot&());
  MOCK_METHOD1(mergeValues, void(const std::unordered_map<std::string, std::string>&));
 
  testing::NiceMock<MockSnapshot> snapshot_;