[GitHub] [arrow-rs] alamb commented on a diff in pull request #4064: Add StructArray Constructors (#3879)

["alamb (via GitHub)" <gi...@apache.org>]

alamb commented on code in PR #4064:
URL: https://github.com/apache/arrow-rs/pull/4064#discussion_r1167833025


##########
arrow-array/src/array/struct_array.rs:
##########
@@ -77,10 +77,136 @@ pub struct StructArray {
     len: usize,
     data_type: DataType,
     nulls: Option<NullBuffer>,
-    pub(crate) fields: Vec<ArrayRef>,
+    fields: Vec<ArrayRef>,
 }
 
 impl StructArray {
+    /// Create a new [`StructArray`] from the provided parts, panicking on failure
+    ///
+    /// # Panics
+    ///
+    /// Panics if [`Self::try_new`] returns an error
+    pub fn new(fields: Fields, arrays: Vec<ArrayRef>, nulls: Option<NullBuffer>) -> Self {
+        Self::try_new(fields, arrays, nulls).unwrap()
+    }
+
+    /// Create a new [`StructArray`] from the provided parts, returning an error on failure
+    ///
+    /// # Errors
+    ///
+    /// Errors if
+    ///
+    /// * `fields.len() != arrays.len()`
+    /// * `fields[i].data_type() != arrays[i].data_type()`
+    /// * `arrays[i].len() != arrays[j].len()`
+    /// * `arrays[i].len() != nulls.len()`
+    /// * `!fields[i].is_nullable() && !nulls.contains(arrays[i].nulls())`
+    pub fn try_new(

Review Comment:
   As in the similar PRs, I think we should add test coverage for these new constructors, especially the error conditions



##########
arrow-array/src/array/struct_array.rs:
##########
@@ -359,37 +485,10 @@ impl std::fmt::Debug for StructArray {
 
 impl From<(Vec<(Field, ArrayRef)>, Buffer)> for StructArray {
     fn from(pair: (Vec<(Field, ArrayRef)>, Buffer)) -> Self {
-        let capacity = pair.0.len();

Review Comment:
   it is really nice that you are making the construction (and validation) of the various array types consistent ❤️ 



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