(arrow-rs) branch main updated: Fix JSON reader panic for non-nullable zero-size FixedSizeList (#9810)

[jeffreyvo]

This is an automated email from the ASF dual-hosted git repository.

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


The following commit(s) were added to refs/heads/main by this push:
     new b1142418b3 Fix JSON reader panic for non-nullable zero-size 
FixedSizeList (#9810)
b1142418b3 is described below

commit b1142418b3d3933cc0409bc6a97f4fbedc537fea
Author: Liam Bao <liam.zw....@gmail.com>
AuthorDate: Wed Apr 29 01:53:00 2026 -0400

    Fix JSON reader panic for non-nullable zero-size FixedSizeList (#9810)
    
    # Which issue does this PR close?
    
    <!--
    We generally require a GitHub issue to be filed for all bug fixes and
    enhancements and this helps us generate change logs for our releases.
    You can link an issue to this PR using the GitHub syntax.
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    - Closes #9780.
    
    # Rationale for this change
    
    <!--
    Why are you proposing this change? If this is already explained clearly
    in the issue then this section is not needed.
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    your changes and offer better suggestions for fixes.
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    # What changes are included in this PR?
    
    <!--
    There is no need to duplicate the description in the issue here but it
    is sometimes worth providing a summary of the individual changes in this
    PR.
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    Use `FixedSizeListArray::try_new_with_length` to avoid panic when
    decoding degenerate non-nullable `FixedSizeList`
    
    # Are these changes tested?
    
    <!--
    We typically require tests for all PRs in order to:
    1. Prevent the code from being accidentally broken by subsequent changes
    2. Serve as another way to document the expected behavior of the code
    
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    Yes
    
    # Are there any user-facing changes?
    
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    Bug fixed
---
 arrow-json/src/reader/list_array.rs |  8 +++++++-
 arrow-json/src/reader/mod.rs        | 26 ++++++++++++++++++++++++++
 2 files changed, 33 insertions(+), 1 deletion(-)

diff --git a/arrow-json/src/reader/list_array.rs 
b/arrow-json/src/reader/list_array.rs
index 778b2e2804..63644964c3 100644
--- a/arrow-json/src/reader/list_array.rs
+++ b/arrow-json/src/reader/list_array.rs
@@ -209,7 +209,13 @@ impl ArrayDecoder for FixedSizeListArrayDecoder {
         let values = self.decoder.decode(tape, &child_pos)?;
         let nulls = nulls.as_mut().and_then(|x| x.finish());
 
-        let array = FixedSizeListArray::try_new(self.field.clone(), self.size, 
values, nulls)?;
+        let array = FixedSizeListArray::try_new_with_length(
+            self.field.clone(),
+            self.size,
+            values,
+            nulls,
+            pos.len(),
+        )?;
         Ok(Arc::new(array))
     }
 }
diff --git a/arrow-json/src/reader/mod.rs b/arrow-json/src/reader/mod.rs
index 3cd45bb824..b0a2c9fc25 100644
--- a/arrow-json/src/reader/mod.rs
+++ b/arrow-json/src/reader/mod.rs
@@ -2369,6 +2369,32 @@ mod tests {
         assert!(values.is_null(5));
     }
 
+    #[test]
+    fn test_fixed_size_list_zero_size_non_nullable() {
+        let buf = r#"
+        {"a": []}
+        {"a": []}
+        {"a": []}
+        "#;
+
+        let field = Field::new_list_field(DataType::Int32, true);
+        let schema = Arc::new(Schema::new(vec![Field::new(
+            "a",
+            DataType::FixedSizeList(Arc::new(field), 0),
+            false,
+        )]));
+
+        let batches = do_read(buf, 1024, false, false, schema);
+        assert_eq!(batches.len(), 1);
+
+        let col = batches[0].column(0).as_fixed_size_list();
+        assert_eq!(col.len(), 3);
+        assert_eq!(col.value_length(), 0);
+
+        let values = col.values().as_primitive::<Int32Type>();
+        assert!(values.values().is_empty());
+    }
+
     #[test]
     fn test_fixed_size_list_wrong_size() {
         let buf = r#"{"a": [1, 2, 3]}"#;