(arrow-go) branch main updated: fix: clarify StringViewBuilder.UnmarshalOne expected type (#897)

[zeroshade]

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zeroshade pushed a commit to branch main
in repository https://gitbox.apache.org/repos/asf/arrow-go.git


The following commit(s) were added to refs/heads/main by this push:
     new 00e949e3 fix: clarify StringViewBuilder.UnmarshalOne expected type 
(#897)
00e949e3 is described below

commit 00e949e3f57498fdf88b36bc9c54e5b2c8580279
Author: Minh Vu <vuhoangmin...@gmail.com>
AuthorDate: Thu Jul 9 20:58:27 2026 +0200

    fix: clarify StringViewBuilder.UnmarshalOne expected type (#897)
    
    ## Summary
    
    ### Problem
    `StringViewBuilder.UnmarshalOne` reports a `json.UnmarshalTypeError`
    with an expected type of `[]byte{}` for unsupported token types.
    
    ### Change
    - Update `StringViewBuilder.UnmarshalOne` to report `reflect.TypeOf("")`
    when an unsupported JSON token is encountered.
    - Add regression test `TestStringViewBuilderUnmarshalOneWrongType` in
    `arrow/array/string_test.go`.
    
    ### Impact
    - Aligns error diagnostics with `StringBuilder` behavior.
    - Makes JSON import debugging clearer for users expecting string inputs.
    
    ### Testing
    - Added a focused regression test that asserts the reported expected
    type is `string` for unsupported JSON token input.
    - No full test run in this PR (single-path, message-type assertion).
---
 arrow/array/string.go      |  2 +-
 arrow/array/string_test.go | 19 +++++++++++++++++++
 2 files changed, 20 insertions(+), 1 deletion(-)

diff --git a/arrow/array/string.go b/arrow/array/string.go
index 559a216c..7c2ab074 100644
--- a/arrow/array/string.go
+++ b/arrow/array/string.go
@@ -778,7 +778,7 @@ func (b *StringViewBuilder) UnmarshalOne(dec *json.Decoder) 
error {
        default:
                return &json.UnmarshalTypeError{
                        Value:  fmt.Sprint(t),
-                       Type:   reflect.TypeOf([]byte{}),
+                       Type:   reflect.TypeOf(string("")),
                        Offset: dec.InputOffset(),
                }
        }
diff --git a/arrow/array/string_test.go b/arrow/array/string_test.go
index 0457b8b3..087da9fe 100644
--- a/arrow/array/string_test.go
+++ b/arrow/array/string_test.go
@@ -25,6 +25,7 @@ import (
        "github.com/apache/arrow-go/v18/arrow/array"
        "github.com/apache/arrow-go/v18/arrow/bitutil"
        "github.com/apache/arrow-go/v18/arrow/memory"
+       "github.com/apache/arrow-go/v18/internal/json"
        "github.com/stretchr/testify/assert"
 )
 
@@ -902,6 +903,24 @@ func TestStringViewBuilder_Empty(t *testing.T) {
        a.Release()
 }
 
+func TestStringViewBuilderUnmarshalOneWrongType(t *testing.T) {
+       mem := memory.NewCheckedAllocator(memory.DefaultAllocator)
+       defer mem.AssertSize(t, 0)
+
+       bldr := array.NewStringViewBuilder(mem)
+       defer bldr.Release()
+
+       dec := json.NewDecoder(bytes.NewReader([]byte(`1`)))
+       err := bldr.UnmarshalOne(dec)
+
+       assert.Error(t, err)
+       var ute *json.UnmarshalTypeError
+       assert.ErrorAs(t, err, &ute)
+       if assert.NotNil(t, ute) {
+               assert.Equal(t, reflect.TypeOf(""), ute.Type)
+       }
+}
+
 // TestStringReset tests the Reset() method on the String type by creating two 
different Strings and then
 // resetting the contents of string2 with the values from string1.
 func TestStringViewReset(t *testing.T) {