Add ExtensionType trait and CanonicalExtensionType enum

arrow-array/src/array/list_view_array.rs

@@ -830,8 +830,8 @@ mod tests {
                 .build()
                 .unwrap(),
         );
-        assert_eq!(string.value_offsets(), &[]);
-        assert_eq!(string.value_sizes(), &[]);
+        assert_eq!(string.value_offsets(), &[] as &[i32; 0]);
+        assert_eq!(string.value_sizes(), &[] as &[i32; 0]);
 
         let string = LargeListViewArray::from(
             ArrayData::builder(DataType::LargeListView(f))
@@ -841,8 +841,8 @@ mod tests {
                 .unwrap(),
         );
         assert_eq!(string.len(), 0);
-        assert_eq!(string.value_offsets(), &[]);
-        assert_eq!(string.value_sizes(), &[]);
+        assert_eq!(string.value_offsets(), &[] as &[i64; 0]);
+        assert_eq!(string.value_sizes(), &[] as &[i64; 0]);
     }
 
     #[test]

arrow-schema/Cargo.toml

@@ -34,21 +34,27 @@ path = "src/lib.rs"
 bench = false
 
 [dependencies]
-serde = { version = "1.0", default-features = false, features = ["derive", "std", "rc"], optional = true }
+serde = { version = "1.0", default-features = false, features = [
+    "derive",
+    "std",
+    "rc",
+], optional = true }
 bitflags = { version = "2.0.0", default-features = false, optional = true }
+serde_json = { version = "1.0", optional = true }
 
 [features]
+canonical_extension_types = ["dep:serde", "dep:serde_json"]
 # Enable ffi support
 ffi = ["bitflags"]
+serde = ["dep:serde"]
 
 [package.metadata.docs.rs]
 features = ["ffi"]
 
 [dev-dependencies]
-serde_json = "1.0"
 bincode = { version = "1.3.3", default-features = false }
 criterion = { version = "0.5", default-features = false }
 
 [[bench]]
 name = "ffi"
-harness = false
+harness = false

arrow-schema/src/extension/canonical/bool8.rs

@@ -0,0 +1,143 @@
+// Licensed to the Apache Software Foundation (ASF) under one
+// or more contributor license agreements.  See the NOTICE file
+// distributed with this work for additional information
+// regarding copyright ownership.  The ASF licenses this file
+// to you under the Apache License, Version 2.0 (the
+// "License"); you may not use this file except in compliance
+// with the License.  You may obtain a copy of the License at
+//
+//   http://www.apache.org/licenses/LICENSE-2.0
+//
+// Unless required by applicable law or agreed to in writing,
+// software distributed under the License is distributed on an
+// "AS IS" BASIS, WITHOUT WARRANTIES OR CONDITIONS OF ANY
+// KIND, either express or implied.  See the License for the
+// specific language governing permissions and limitations
+// under the License.
+
+//! 8-bit Boolean
+//!
+//! <https://arrow.apache.org/docs/format/CanonicalExtensions.html#bit-boolean>
+
+use crate::{extension::ExtensionType, ArrowError, DataType};
+
+/// The extension type for `8-bit Boolean`.
+///
+/// Extension name: `arrow.bool8`.
+///
+/// The storage type of the extension is `Int8` where:
+/// - false is denoted by the value 0.
+/// - true can be specified using any non-zero value. Preferably 1.
+///
+/// <https://arrow.apache.org/docs/format/CanonicalExtensions.html#bit-boolean>
+#[derive(Debug, Default, Clone, Copy, PartialEq)]
+pub struct Bool8;
+
+impl ExtensionType for Bool8 {
+    const NAME: &'static str = "arrow.bool8";
+
+    type Metadata = &'static str;
+
+    fn metadata(&self) -> &Self::Metadata {
+        &""
+    }
+
+    fn serialize_metadata(&self) -> Option<String> {
+        Some(String::default())
+    }
+
+    fn deserialize_metadata(metadata: Option<&str>) -> Result<Self::Metadata, ArrowError> {
+        const ERR: &str = "Bool8 extension type expects an empty string as metadata";
+        metadata.map_or_else(
+            || Err(ArrowError::InvalidArgumentError(ERR.to_owned())),
+            |value| match value {
+                "" => Ok(""),
+                _ => Err(ArrowError::InvalidArgumentError(ERR.to_owned())),
+            },
+        )
+    }
+
+    fn supports_data_type(&self, data_type: &DataType) -> Result<(), ArrowError> {
+        match data_type {
+            DataType::Int8 => Ok(()),
+            data_type => Err(ArrowError::InvalidArgumentError(format!(
+                "Bool8 data type mismatch, expected Int8, found {data_type}"
+            ))),
+        }
+    }
+
+    fn try_new(data_type: &DataType, _metadata: Self::Metadata) -> Result<Self, ArrowError> {
+        Self.supports_data_type(data_type).map(|_| Self)
+    }
+}
+
+#[cfg(test)]
+mod tests {
+    #[cfg(feature = "canonical_extension_types")]
+    use crate::extension::CanonicalExtensionType;
+    use crate::{
+        extension::{EXTENSION_TYPE_METADATA_KEY, EXTENSION_TYPE_NAME_KEY},
+        Field,
+    };
+
+    use super::*;
+
+    #[test]
+    fn valid() -> Result<(), ArrowError> {
+        let mut field = Field::new("", DataType::Int8, false);
+        field.try_with_extension_type(Bool8)?;
+        field.try_extension_type::<Bool8>()?;
+        #[cfg(feature = "canonical_extension_types")]
+        assert_eq!(
+            field.try_canonical_extension_type()?,
+            CanonicalExtensionType::Bool8(Bool8)
+        );
+
+        Ok(())
+    }
+
+    #[test]
+    #[should_panic(expected = "Field extension type name missing")]
+    fn missing_name() {
+        let field = Field::new("", DataType::Int8, false).with_metadata(
+            [(EXTENSION_TYPE_METADATA_KEY.to_owned(), "".to_owned())]
+                .into_iter()
+                .collect(),
+        );
+        field.extension_type::<Bool8>();
+    }
+
+    #[test]
+    #[should_panic(expected = "expected Int8, found Boolean")]
+    fn invalid_type() {
+        Field::new("", DataType::Boolean, false).with_extension_type(Bool8);
+    }
+
+    #[test]
+    #[should_panic(expected = "Bool8 extension type expects an empty string as metadata")]
+    fn missing_metadata() {
+        let field = Field::new("", DataType::Int8, false).with_metadata(
+            [(EXTENSION_TYPE_NAME_KEY.to_owned(), Bool8::NAME.to_owned())]
+                .into_iter()
+                .collect(),
+        );
+        field.extension_type::<Bool8>();
+    }
+
+    #[test]
+    #[should_panic(expected = "Bool8 extension type expects an empty string as metadata")]
+    fn invalid_metadata() {
+        let field = Field::new("", DataType::Int8, false).with_metadata(
+            [
+                (EXTENSION_TYPE_NAME_KEY.to_owned(), Bool8::NAME.to_owned()),
+                (
+                    EXTENSION_TYPE_METADATA_KEY.to_owned(),
+                    "non-empty".to_owned(),
+                ),
+            ]
+            .into_iter()
+            .collect(),
+        );
+        field.extension_type::<Bool8>();
+    }
+}