GH-38419: [MATLAB] Implement a ClassTypeValidator class that validates a MATLAB cell array contains only values of the same class type.

matlab/src/matlab/+arrow/+array/+internal/+list/ClassTypeValidator.m

@@ -0,0 +1,47 @@
+% Licensed to the Apache Software Foundation (ASF) under one or more
+% contributor license agreements.  See the NOTICE file distributed with
+% this work for additional information regarding copyright ownership.
+% The ASF licenses this file to you under the Apache License, Version
+% 2.0 (the "License"); you may not use this file except in compliance
+% with the License.  You may obtain a copy of the License at
+%
+%   http://www.apache.org/licenses/LICENSE-2.0
+%
+% Unless required by applicable law or agreed to in writing, software
+% distributed under the License is distributed on an "AS IS" BASIS,
+% WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or
+% implied.  See the License for the specific language governing
+% permissions and limitations under the License.
+
+classdef ClassTypeValidator < arrow.array.internal.list.Validator
+
+    properties (GetAccess=public, SetAccess=private)
+        ClassName(1, 1) string
+    end
+
+    methods
+        function obj = ClassTypeValidator(data)
+            obj.ClassName = class(data);
+        end
+
+        function validateElement(obj, element)
+           if ~isa(element, obj.ClassName)
+               id = "arrow:array:list:ClassTypeMismatch";
+               fmt = "Expected all cell array elements to have class type " + ...
+                   """%s"", but encountered an element whose class type is" + ...
+                   " ""%s"".";
+               msg = compose(fmt, obj.ClassName, class(element));
+              error(id, msg);
+           end
+        end
+
+        function length = getElementLength(~, element)
+            length = numel(element);
+        end
+
+        function C = reshapeCellElements(~, C)
+            C = cellfun(@(elem) reshape(elem, [], 1), C, UniformOutput=false);
+        end
+    end
+end
+

matlab/src/matlab/+arrow/+array/+internal/+list/Validator.m

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+%VALIDATOR Defines interface used to validate MATLAB cell arrays
+%can be converted into Arrow List arrays.
+
+% Licensed to the Apache Software Foundation (ASF) under one or more
+% contributor license agreements.  See the NOTICE file distributed with
+% this work for additional information regarding copyright ownership.
+% The ASF licenses this file to you under the Apache License, Version
+% 2.0 (the "License"); you may not use this file except in compliance
+% with the License.  You may obtain a copy of the License at
+%
+%   http://www.apache.org/licenses/LICENSE-2.0
+%
+% Unless required by applicable law or agreed to in writing, software
+% distributed under the License is distributed on an "AS IS" BASIS,
+% WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or
+% implied.  See the License for the specific language governing
+% permissions and limitations under the License.
+
+classdef Validator
+
+    methods (Abstract)
+        tf = validateElement(obj, element)
+
+        length = getElementLength(obj, element)
+
+        C = reshapeCellElements(obj, element)
+    end
+end

matlab/test/arrow/array/list/tClassTypeValidator.m

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+%TCLASSTYPEVALIDATOR Unit tests for arrow.array.internal.list.ClassTypeValidator
+
+% Licensed to the Apache Software Foundation (ASF) under one or more
+% contributor license agreements.  See the NOTICE file distributed with
+% this work for additional information regarding copyright ownership.
+% The ASF licenses this file to you under the Apache License, Version
+% 2.0 (the "License"); you may not use this file except in compliance
+% with the License.  You may obtain a copy of the License at
+%
+%   http://www.apache.org/licenses/LICENSE-2.0
+%
+% Unless required by applicable law or agreed to in writing, software
+% distributed under the License is distributed on an "AS IS" BASIS,
+% WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or
+% implied.  See the License for the specific language governing
+% permissions and limitations under the License.
+
+classdef tClassTypeValidator < matlab.unittest.TestCase
+
+    methods (Test)
+        function Smoke(testCase)
+            import arrow.array.internal.list.ClassTypeValidator
+            validator = ClassTypeValidator("Sample Data");
+            testCase.verifyInstanceOf(validator, "arrow.array.internal.list.ClassTypeValidator");
+        end
+
+        function ClassNameGetter(testCase)
+            % Verify the ClassName getter returns the expected scalar
+            % string.
+            import arrow.array.internal.list.ClassTypeValidator
+
+            validator = ClassTypeValidator("Sample Data");
+            testCase.verifyEqual(validator.ClassName, "string");
+        end
+
+        function ClassNameNoSetter(testCase)
+            % Verify ClassName property is not settable.
+            import arrow.array.internal.list.ClassTypeValidator
+
+            validator = ClassTypeValidator(1);
+            fcn = @() setfield(validator, "ClassName", "duration");
+            testCase.verifyError(fcn, "MATLAB:class:SetProhibited");
+        end
+
+        function ValidateElementNoThrow(testCase) %#ok<MANU>
+            % Verify validateElement does not throw an exception
+            % if class type of the input element matches the ClassName
+            % property value.
+            import arrow.array.internal.list.ClassTypeValidator
+
+            validator = ClassTypeValidator(1);
+            validator.validateElement(2);
+            validator.validateElement([1 2 3]);
+            validator.validateElement([1; 2; 3; 3]);
+            validator.validateElement([5 6; 7 8]);
+            validator.validateElement(double.empty(0, 1));
+        end
+
+        function ValidateElementClassTypeMismatchError(testCase)
+            % Verify validateElement throws an exception whose identifier
+            % is "arrow:array:list:ClassTypeMismatch" if the input
+            % element's class type does not match the ClassName property
+            % value.
+            import arrow.array.internal.list.ClassTypeValidator
+
+            % validator will expect all elements to be of type double, since "1" is a double.
+            validator = ClassTypeValidator(1);
+            errorID = "arrow:array:list:ClassTypeMismatch";
+            testCase.verifyError(@() validator.validateElement("A"), errorID);
+            testCase.verifyError(@() validator.validateElement(uint8([1 2])), errorID);
+            testCase.verifyError(@() validator.validateElement(datetime(2023, 1, 1)), errorID);
+        end
+
+        function GetElementLength(testCase)
+            % Verify getElementLength returns the expected length values
+            % for the given input arrays.
+            import arrow.array.internal.list.ClassTypeValidator
+
+            validator = ClassTypeValidator(1);
+            testCase.verifyEqual(validator.getElementLength(2), 1);
+            testCase.verifyEqual(validator.getElementLength([1 2; 3 4]), 4);
+            testCase.verifyEqual(validator.getElementLength(double.empty(1, 0)), 0);
+        end
+
+        function ReshapeCellElements(testCase)
+            % Verify reshapeCellElements reshapes all elements in the input
+            % cell array into column vectors.
+            import arrow.array.internal.list.ClassTypeValidator
+
+            validator = ClassTypeValidator(1);
+            C = {[1 2 3], [4; 5], [6 7; 8 9], double.empty(1, 0), 10};
+            act = validator.reshapeCellElements(C);
+            exp = {[1; 2; 3], [4; 5], [6; 8; 7; 9], double.empty(0, 1), 10};
+            testCase.verifyEqual(act, exp);
+        end
+
+    end
+
+end