implement DataType::try_form(&str) (#5994)

* implement "DataType::try_form(&str)"

* add missing file

* add FromStr as well as TryFrom<&str>

* fmt

Author: samuelcolvin

arrow-schema/src/datatype.rs

@@ -16,9 +16,10 @@
 // under the License.
 
 use std::fmt;
+use std::str::FromStr;
 use std::sync::Arc;
 
-use crate::{Field, FieldRef, Fields, UnionFields};
+use crate::{ArrowError, Field, FieldRef, Fields, UnionFields};
 
 /// The set of datatypes that are supported by this implementation of Apache Arrow.
 ///
@@ -373,6 +374,35 @@ impl fmt::Display for DataType {
     }
 }
 
+/// Parses `str` into a `DataType`.
+///
+/// This is the reverse of [`DataType`]'s `Display`
+/// impl, and maintains the invariant that
+/// `DataType::try_from(&data_type.to_string()).unwrap() == data_type`
+///
+/// # Example
+/// ```
+/// use arrow_schema::DataType;
+///
+/// let data_type: DataType = "Int32".parse().unwrap();
+/// assert_eq!(data_type, DataType::Int32);
+/// ```
+impl FromStr for DataType {
+    type Err = ArrowError;
+
+    fn from_str(s: &str) -> Result<Self, Self::Err> {
+        crate::datatype_parse::parse_data_type(s)
+    }
+}
+
+impl TryFrom<&str> for DataType {
+    type Error = ArrowError;
+
+    fn try_from(value: &str) -> Result<Self, Self::Error> {
+        value.parse()
+    }
+}
+
 impl DataType {
     /// Returns true if the type is primitive: (numeric, temporal).
     #[inline]
@@ -985,4 +1015,16 @@ mod tests {
             UnionMode::Dense,
         );
     }
+
+    #[test]
+    fn test_try_from_str() {
+        let data_type: DataType = "Int32".try_into().unwrap();
+        assert_eq!(data_type, DataType::Int32);
+    }
+
+    #[test]
+    fn test_from_str() {
+        let data_type: DataType = "UInt64".parse().unwrap();
+        assert_eq!(data_type, DataType::UInt64);
+    }
 }