SpeculationRules: Dedup and sort tags passed to SpeculationRulesTags

This CL dedups and sorts given speculation rules tags by using std::set.
Also, this CL adds unit tests for the class.

Bug: 381687257
Change-Id: Ibbe4f4b5232ba2674bf46b362662f62b333869a7
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/6399977
Commit-Queue: Hiroki Nakagawa <nhiroki@chromium.org>
Reviewed-by: Huanpo Lin <robertlin@chromium.org>
Reviewed-by: Taiyo Mizuhashi <taiyo@chromium.org>
Cr-Commit-Position: refs/heads/main@{#1439351}

content/browser/preloading/speculation_rules/speculation_rules_tags.cc

@@ -11,8 +11,11 @@ namespace content {
 
 SpeculationRulesTags::SpeculationRulesTags() = default;
 SpeculationRulesTags::SpeculationRulesTags(
-    std::vector<std::optional<std::string>> tags)
-    : tags_(std::move(tags)) {}
+    std::vector<std::optional<std::string>> tags) {
+  for (auto& tag : tags) {
+    tags_.insert(std::move(tag));
+  }
+}
 
 SpeculationRulesTags::~SpeculationRulesTags() = default;
 

content/browser/preloading/speculation_rules/speculation_rules_tags.h

@@ -5,6 +5,7 @@
 #ifndef CONTENT_BROWSER_PRELOADING_SPECULATION_RULES_SPECULATION_RULES_TAGS_H_
 #define CONTENT_BROWSER_PRELOADING_SPECULATION_RULES_SPECULATION_RULES_TAGS_H_
 
+#include <set>
 #include <string>
 #include <vector>
 
@@ -19,6 +20,7 @@ namespace content {
 class CONTENT_EXPORT SpeculationRulesTags {
  public:
   SpeculationRulesTags();
+  // TODO(crbug.com/381687257): Use std::set instead of std::vector.
   explicit SpeculationRulesTags(std::vector<std::optional<std::string>> tags);
   ~SpeculationRulesTags();
 
@@ -33,7 +35,7 @@ class CONTENT_EXPORT SpeculationRulesTags {
  private:
   net::structured_headers::List ConvertStringToStructuredHeader();
 
-  std::vector<std::optional<std::string>> tags_;
+  std::set<std::optional<std::string>> tags_;
 };
 
 }  // namespace content

content/browser/preloading/speculation_rules/speculation_rules_tags_unittest.cc

@@ -0,0 +1,64 @@
+// Copyright 2025 The Chromium Authors
+// Use of this source code is governed by a BSD-style license that can be
+// found in the LICENSE file.
+
+#include "content/browser/preloading/speculation_rules/speculation_rules_tags.h"
+
+#include "testing/gtest/include/gtest/gtest.h"
+
+namespace content {
+namespace {
+
+using Tags = std::vector<std::optional<std::string>>;
+
+void TestTags(const Tags& tags, const std::string& expected) {
+  EXPECT_EQ(expected, SpeculationRulesTags(tags).ConvertStringToHeaderString());
+}
+
+// Each string tag should be wrapped with double quotes during parsing.
+// https://www.rfc-editor.org/rfc/rfc8941.html#name-serializing-a-string
+TEST(SpeculationRulesTagsTest, Basic) {
+  TestTags({R"(my-rules)"}, R"("my-rules")");
+  TestTags({R"(my-rules1)", R"(my-rules2)"}, R"("my-rules1", "my-rules2")");
+}
+
+// No tags should be parsed as null token.
+// https://www.rfc-editor.org/rfc/rfc8941.html#section-4.1.7
+TEST(SpeculationRulesTagsTest, NoTags) {
+  TestTags({std::nullopt}, R"(null)");
+  TestTags({std::nullopt, R"(my-rules)"}, R"(null, "my-rules")");
+  TestTags({std::nullopt, R"(my-rules)", R"(null)"},
+           R"(null, "my-rules", "null")");
+}
+
+// A double quote (DQUOTE) should be converted to \" during parsing:
+// https://www.rfc-editor.org/rfc/rfc8941.html#name-serializing-a-string
+TEST(SpeculationRulesTagsTest, DoubleQuote) {
+  TestTags({R"(")"}, R"("\"")");
+  TestTags({R"("")"}, R"("\"\"")");
+  TestTags({R"(my"rules)"}, R"("my\"rules")");
+  TestTags({R"(my-rules)", R"(")"}, R"("\"", "my-rules")");
+}
+
+// A backslash should be converted to \\ during parsing:
+// https://www.rfc-editor.org/rfc/rfc8941.html#name-serializing-a-string
+TEST(SpeculationRulesTagsTest, BackSlash) {
+  TestTags({R"(\)"}, R"("\\")");
+  TestTags({R"(\\)"}, R"("\\\\")");
+  TestTags({R"(my\rules)"}, R"("my\\rules")");
+  TestTags({R"(my-rules)", R"(\)"}, R"("\\", "my-rules")");
+}
+
+TEST(SpeculationRulesTagsTest, Duplicate) {
+  TestTags({std::nullopt, R"(my-rules)", R"(my-rules)"}, R"(null, "my-rules")");
+  TestTags({std::nullopt, std::nullopt, R"(my-rules)"}, R"(null, "my-rules")");
+}
+
+TEST(SpeculationRulesTagsTest, Sort) {
+  TestTags({R"(def)", R"(jkl)", R"(def)", R"(null)", std::nullopt, R"(abc)",
+            std::nullopt, R"(ghi)"},
+           R"(null, "abc", "def", "ghi", "jkl", "null")");
+}
+
+}  // namespace
+}  // namespace content

content/test/BUILD.gn

@@ -2698,6 +2698,7 @@ test("content_unittests") {
     "../browser/preloading/prerender/prerender_metrics_unittest.cc",
     "../browser/preloading/prerenderer_impl_unittest.cc",
     "../browser/preloading/speculation_rules/speculation_host_impl_unittest.cc",
+    "../browser/preloading/speculation_rules/speculation_rules_tags_unittest.cc",
     "../browser/presentation/presentation_service_impl_unittest.cc",
     "../browser/private_aggregation/private_aggregation_budget_key_unittest.cc",
     "../browser/private_aggregation/private_aggregation_budget_storage_unittest.cc",