From f02a5bd3f3ecc78982dc307beb73ee4b0894b5a1 Mon Sep 17 00:00:00 2001
From: slinkydeveloper <francescoguard@gmail.com>
Date: Fri, 19 Apr 2024 11:05:03 +0200
Subject: [PATCH 1/2] Add more info to data mismatch error

---
 arrow_convert/src/deserialize/mod.rs | 10 +++++++---
 1 file changed, 7 insertions(+), 3 deletions(-)

diff --git a/arrow_convert/src/deserialize/mod.rs b/arrow_convert/src/deserialize/mod.rs
index de5e963..baeba9f 100644
--- a/arrow_convert/src/deserialize/mod.rs
+++ b/arrow_convert/src/deserialize/mod.rs
@@ -424,9 +424,13 @@ where
     <ArrowType as ArrowDeserialize>::ArrayType: ArrowArrayIterable,
 {
     if &<ArrowType as ArrowField>::data_type() != arr.data_type() {
-        Err(arrow::error::ArrowError::InvalidArgumentError(
-            "Data type mismatch".to_string(),
-        ))
+        Err(arrow::error::ArrowError::InvalidArgumentError(format!(
+            "Data type mismatch. Expected type={} is_nullable={}, but was type={} is_nullable={}",
+            &<ArrowType as ArrowField>::data_type(),
+            &<ArrowType as ArrowField>::is_nullable(),
+            arr.data_type(),
+            arr.is_nullable()
+        )))
     } else {
         Ok(arrow_array_deserialize_iterator_internal::<
             Element,

From 0d52c0d53701b0dd168bb31f0a26ed2e9d96775e Mon Sep 17 00:00:00 2001
From: slinkydeveloper <francescoguard@gmail.com>
Date: Fri, 19 Apr 2024 11:34:23 +0200
Subject: [PATCH 2/2] Expanded an existing test, plus format using alternative
 formatting.

---
 arrow_convert/src/deserialize/mod.rs    |  2 +-
 arrow_convert/tests/test_deserialize.rs | 26 ++++++++++++++++++++++---
 2 files changed, 24 insertions(+), 4 deletions(-)

diff --git a/arrow_convert/src/deserialize/mod.rs b/arrow_convert/src/deserialize/mod.rs
index baeba9f..c58d292 100644
--- a/arrow_convert/src/deserialize/mod.rs
+++ b/arrow_convert/src/deserialize/mod.rs
@@ -425,7 +425,7 @@ where
 {
     if &<ArrowType as ArrowField>::data_type() != arr.data_type() {
         Err(arrow::error::ArrowError::InvalidArgumentError(format!(
-            "Data type mismatch. Expected type={} is_nullable={}, but was type={} is_nullable={}",
+            "Data type mismatch. Expected type={:#?} is_nullable={}, but was type={:#?} is_nullable={}",
             &<ArrowType as ArrowField>::data_type(),
             &<ArrowType as ArrowField>::is_nullable(),
             arr.data_type(),
diff --git a/arrow_convert/tests/test_deserialize.rs b/arrow_convert/tests/test_deserialize.rs
index c12cef0..cb3f8e4 100644
--- a/arrow_convert/tests/test_deserialize.rs
+++ b/arrow_convert/tests/test_deserialize.rs
@@ -1,6 +1,7 @@
 use arrow::buffer::ScalarBuffer;
 use arrow::error::Result;
 use arrow::{array::*, buffer::Buffer};
+use arrow_convert::field::ArrowField;
 use arrow_convert::{deserialize::*, serialize::*, ArrowDeserialize, ArrowField, ArrowSerialize};
 
 #[test]
@@ -31,6 +32,16 @@ fn test_deserialize_iterator() {
     }
 }
 
+fn data_mismatch_error<Expected: ArrowField, Actual: ArrowField>() -> arrow::error::ArrowError {
+    arrow::error::ArrowError::InvalidArgumentError(format!(
+        "Data type mismatch. Expected type={:#?} is_nullable={}, but was type={:#?} is_nullable={}",
+        Expected::data_type(),
+        Expected::is_nullable(),
+        Actual::data_type(),
+        Actual::is_nullable()
+    ))
+}
+
 #[test]
 fn test_deserialize_schema_mismatch_error() {
     #[derive(Debug, Clone, PartialEq, ArrowField, ArrowSerialize, ArrowDeserialize)]
@@ -45,12 +56,18 @@ fn test_deserialize_schema_mismatch_error() {
     let arr1 = vec![S1 { a: 1 }, S1 { a: 2 }];
     let arr1: ArrayRef = arr1.try_into_arrow().unwrap();
     let result: Result<Vec<S2>> = arr1.try_into_collection();
-    assert!(result.is_err());
+    assert_eq!(
+        result.unwrap_err().to_string(),
+        data_mismatch_error::<S2, S1>().to_string()
+    );
 
     let arr1 = vec![S1 { a: 1 }, S1 { a: 2 }];
     let arr1: ArrayRef = arr1.try_into_arrow().unwrap();
     let result: Result<Vec<_>> = arr1.try_into_collection_as_type::<S2>();
-    assert!(result.is_err());
+    assert_eq!(
+        result.unwrap_err().to_string(),
+        data_mismatch_error::<S2, S1>().to_string()
+    );
 }
 
 #[test]
@@ -76,7 +93,10 @@ fn test_deserialize_large_types_schema_mismatch_error() {
     let arr1: ArrayRef = arr1.try_into_arrow().unwrap();
 
     let result: Result<Vec<S2>> = arr1.try_into_collection();
-    assert!(result.is_err());
+    assert_eq!(
+        result.unwrap_err().to_string(),
+        data_mismatch_error::<S2, S1>().to_string()
+    );
 }
 
 #[test]