feat: add doc attribute to SchemaField (#96)

Author: wgtmac

src/iceberg/schema_field.cc

@@ -27,20 +27,21 @@
 namespace iceberg {
 
 SchemaField::SchemaField(int32_t field_id, std::string name, std::shared_ptr<Type> type,
-                         bool optional)
+                         bool optional, std::string doc)
     : field_id_(field_id),
       name_(std::move(name)),
       type_(std::move(type)),
-      optional_(optional) {}
+      optional_(optional),
+      doc_(std::move(doc)) {}
 
 SchemaField SchemaField::MakeOptional(int32_t field_id, std::string name,
-                                      std::shared_ptr<Type> type) {
-  return SchemaField(field_id, std::move(name), std::move(type), true);
+                                      std::shared_ptr<Type> type, std::string doc) {
+  return {field_id, std::move(name), std::move(type), true, std::move(doc)};
 }
 
 SchemaField SchemaField::MakeRequired(int32_t field_id, std::string name,
-                                      std::shared_ptr<Type> type) {
-  return SchemaField(field_id, std::move(name), std::move(type), false);
+                                      std::shared_ptr<Type> type, std::string doc) {
+  return {field_id, std::move(name), std::move(type), false, std::move(doc)};
 }
 
 int32_t SchemaField::field_id() const { return field_id_; }
@@ -51,9 +52,13 @@ const std::shared_ptr<Type>& SchemaField::type() const { return type_; }
 
 bool SchemaField::optional() const { return optional_; }
 
+std::string_view SchemaField::doc() const { return doc_; }
+
 std::string SchemaField::ToString() const {
-  return std::format("{} ({}): {} ({})", name_, field_id_, *type_,
-                     optional_ ? "optional" : "required");
+  std::string result = std::format("{} ({}): {} ({}){}", name_, field_id_, *type_,
+                                   optional_ ? "optional" : "required",
+                                   !doc_.empty() ? std::format(" - {}", doc_) : "");
+  return result;
 }
 
 bool SchemaField::Equals(const SchemaField& other) const {

src/iceberg/schema_field.h

@@ -44,15 +44,16 @@ class ICEBERG_EXPORT SchemaField : public iceberg::util::Formattable {
   /// \param[in] name The field name.
   /// \param[in] type The field type.
   /// \param[in] optional Whether values of this field are required or nullable.
+  /// \param[in] doc Optional documentation string for the field.
   SchemaField(int32_t field_id, std::string name, std::shared_ptr<Type> type,
-              bool optional);
+              bool optional, std::string doc = {});
 
   /// \brief Construct an optional (nullable) field.
   static SchemaField MakeOptional(int32_t field_id, std::string name,
-                                  std::shared_ptr<Type> type);
+                                  std::shared_ptr<Type> type, std::string doc = {});
   /// \brief Construct a required (non-null) field.
   static SchemaField MakeRequired(int32_t field_id, std::string name,
-                                  std::shared_ptr<Type> type);
+                                  std::shared_ptr<Type> type, std::string doc = {});
 
   /// \brief Get the field ID.
   [[nodiscard]] int32_t field_id() const;
@@ -66,6 +67,9 @@ class ICEBERG_EXPORT SchemaField : public iceberg::util::Formattable {
   /// \brief Get whether the field is optional.
   [[nodiscard]] bool optional() const;
 
+  /// \brief Get the field documentation.
+  std::string_view doc() const;
+
   [[nodiscard]] std::string ToString() const override;
 
   friend bool operator==(const SchemaField& lhs, const SchemaField& rhs) {
@@ -84,6 +88,7 @@ class ICEBERG_EXPORT SchemaField : public iceberg::util::Formattable {
   std::string name_;
   std::shared_ptr<Type> type_;
   bool optional_;
+  std::string doc_;
 };
 
 }  // namespace iceberg

test/schema_field_test.cc

@@ -79,3 +79,29 @@ TEST(SchemaFieldTest, Equality) {
   ASSERT_EQ(field1, field6);
   ASSERT_EQ(field6, field1);
 }
+
+TEST(SchemaFieldTest, WithDoc) {
+  {
+    iceberg::SchemaField field(/*field_id=*/1, /*name=*/"foo",
+                               std::make_shared<iceberg::IntType>(),
+                               /*optional=*/false, /*doc=*/"Field documentation");
+    EXPECT_EQ(1, field.field_id());
+    EXPECT_EQ("foo", field.name());
+    EXPECT_EQ(iceberg::TypeId::kInt, field.type()->type_id());
+    EXPECT_FALSE(field.optional());
+    EXPECT_EQ("Field documentation", field.doc());
+    EXPECT_EQ("foo (1): int (required) - Field documentation", field.ToString());
+  }
+  {
+    iceberg::SchemaField field = iceberg::SchemaField::MakeOptional(
+        /*field_id=*/2, /*name=*/"bar",
+        /*type=*/std::make_shared<iceberg::FixedType>(10),
+        /*doc=*/"Field with 10 bytes");
+    EXPECT_EQ(2, field.field_id());
+    EXPECT_EQ("bar", field.name());
+    EXPECT_EQ(iceberg::FixedType(10), *field.type());
+    EXPECT_TRUE(field.optional());
+    EXPECT_EQ("Field with 10 bytes", field.doc());
+    EXPECT_EQ("bar (2): fixed(10) (optional) - Field with 10 bytes", field.ToString());
+  }
+}