[toolchain] Add simpler mechanism for matching YAML output in tests. (#583)

toolchain/common/yaml_test_helpers.cpp

@@ -0,0 +1,110 @@
+// Part of the Carbon Language project, under the Apache License v2.0 with LLVM
+// Exceptions. See /LICENSE for license information.
+// SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
+
+#include "toolchain/common/yaml_test_helpers.h"
+
+#include "llvm/Support/YAMLParser.h"
+
+namespace Carbon::Testing::Yaml {
+
+static auto Parse(llvm::yaml::Node* node) -> Value {
+  if (!node) {
+    return Value{ErrorValue()};
+  }
+
+  switch (node->getType()) {
+    case llvm::yaml::Node::NK_Null:
+      return Value{NullValue()};
+
+    case llvm::yaml::Node::NK_Scalar: {
+      llvm::SmallString<128> storage;
+      return Value{
+          llvm::cast<llvm::yaml::ScalarNode>(*node).getValue(storage).str()};
+    }
+
+    case llvm::yaml::Node::NK_BlockScalar:
+      return Value{
+          llvm::cast<llvm::yaml::BlockScalarNode>(*node).getValue().str()};
+
+    case llvm::yaml::Node::NK_Mapping: {
+      MappingValue v;
+      for (llvm::yaml::KeyValueNode& kv :
+           llvm::cast<llvm::yaml::MappingNode>(*node)) {
+        Value key = Parse(kv.getKey());
+        Value value = Parse(kv.getValue());
+        v.emplace_back(std::move(key), std::move(value));
+      }
+      return Value{std::move(v)};
+    }
+
+    case llvm::yaml::Node::NK_Sequence: {
+      SequenceValue v;
+      for (llvm::yaml::Node& n : llvm::cast<llvm::yaml::SequenceNode>(*node)) {
+        v.push_back(Parse(&n));
+      }
+      return Value{std::move(v)};
+    }
+
+    case llvm::yaml::Node::NK_Alias:
+      return Value{AliasValue()};
+
+    case llvm::yaml::Node::NK_KeyValue:
+      llvm_unreachable("should only exist as child of mapping");
+  }
+
+  llvm_unreachable("unknown yaml node kind");
+}
+
+auto Value::FromText(llvm::StringRef text) -> SequenceValue {
+  llvm::SourceMgr sm;
+  llvm::yaml::Stream yaml_stream(text, sm);
+
+  SequenceValue result;
+  for (llvm::yaml::Document& document : yaml_stream) {
+    result.push_back(Parse(document.getRoot()));
+  }
+  return result;
+}
+
+auto operator<<(std::ostream& os, const Value& v) -> std::ostream& {
+  // Variant visitor that prints the value in the form of code to recreate the
+  // value.
+  struct Printer {
+    std::ostream& out;
+    auto operator()(NullValue) -> void { out << "Yaml::NullValue()"; }
+    auto operator()(AliasValue) -> void { out << "Yaml::AliasValue()"; }
+    auto operator()(ErrorValue) -> void { out << "Yaml::ErrorValue()"; }
+    auto operator()(const ScalarValue& v) -> void { out << std::quoted(v); }
+    auto operator()(const MappingValue& v) -> void {
+      out << "Yaml::MappingValue{";
+      bool first = true;
+      for (auto& [key, value] : v) {
+        if (first) {
+          first = false;
+        } else {
+          out << ", ";
+        }
+        out << "{" << key << ", " << value << "}";
+      }
+      out << "}";
+    }
+    auto operator()(const SequenceValue& v) -> void {
+      out << "Yaml::SequenceValue{";
+      bool first = true;
+      for (auto& value : v) {
+        if (first) {
+          first = false;
+        } else {
+          out << ", ";
+        }
+        out << value;
+      }
+      out << "}";
+    }
+  };
+  std::visit(Printer{os}, v);
+  return os;
+}
+
+}  // namespace Carbon::Testing::Yaml