Add TagSet::DebugString(). (#179)

Author: g-easy

opencensus/stats/internal/tag_set.cc

@@ -20,6 +20,8 @@
 #include <utility>
 #include <vector>
 
+#include "absl/strings/str_cat.h"
+#include "absl/strings/str_join.h"
 #include "absl/strings/string_view.h"
 #include "opencensus/common/internal/hash_mix.h"
 #include "opencensus/stats/tag_key.h"
@@ -61,5 +63,17 @@ bool TagSet::operator==(const TagSet& other) const {
   return tags_ == other.tags_;
 }
 
+std::string TagSet::DebugString() const {
+  return absl::StrCat(
+      "{",
+      absl::StrJoin(
+          tags_, ", ",
+          [](std::string* o, std::pair<const TagKey&, const std::string&> kv) {
+            absl::StrAppend(o, "\"", kv.first.name(), "\": \"", kv.second,
+                            "\"");
+          }),
+      "}");
+}
+
 }  // namespace stats
 }  // namespace opencensus

opencensus/stats/internal/tag_set_test.cc

@@ -14,6 +14,7 @@
 
 #include "opencensus/stats/tag_set.h"
 
+#include <iostream>
 #include <string>
 #include <unordered_map>
 #include <utility>
@@ -26,6 +27,8 @@ namespace opencensus {
 namespace stats {
 namespace {
 
+using ::testing::HasSubstr;
+
 TEST(TagSetTest, ConstructorsEquivalent) {
   TagKey key = TagKey::Register("k");
   const std::vector<std::pair<TagKey, std::string>> tags({{key, "v"}});
@@ -89,6 +92,18 @@ TEST(TagSetTest, UnorderedMap) {
   EXPECT_EQ(1, map.erase(ts));
 }
 
+TEST(TagSetTest, DebugStringContainsTags) {
+  TagKey k1 = TagKey::Register("key1");
+  TagKey k2 = TagKey::Register("key2");
+  TagSet ts({{k1, "value1"}, {k2, "value2"}});
+  const std::string s = ts.DebugString();
+  std::cout << s << "\n";
+  EXPECT_THAT(s, HasSubstr("key1"));
+  EXPECT_THAT(s, HasSubstr("value1"));
+  EXPECT_THAT(s, HasSubstr("key2"));
+  EXPECT_THAT(s, HasSubstr("value2"));
+}
+
 }  // namespace
 }  // namespace stats
 }  // namespace opencensus

opencensus/stats/tag_set.h

@@ -53,6 +53,10 @@ class TagSet final {
   bool operator==(const TagSet& other) const;
   bool operator!=(const TagSet& other) const { return !(*this == other); }
 
+  // Returns a human-readable string for debugging. Do not rely on its format or
+  // try to parse it. Do not use it to retrieve tags.
+  std::string DebugString() const;
+
  private:
   void Initialize();