Fix several CCE issues in query expressions that has string and xml types as the expected type.

compiler/ballerina-lang/src/main/java/org/wso2/ballerinalang/compiler/desugar/QueryDesugar.java

@@ -297,13 +297,14 @@ BLangStatementExpression desugar(BLangQueryExpr queryExpr, SymbolEnv env,
             onConflictExpr = null;
         } else {
             BType refType = Types.getReferredType(queryExpr.getBType());
-            if (isXml(refType)) {
+            BType safeType = types.getSafeType(refType, true, true);
+            if (isXml(safeType)) {
                 if (types.isSubTypeOfReadOnly(refType, env)) {
                     isReadonly.value = true;
                 }
                 result = getStreamFunctionVariableRef(queryBlock, QUERY_TO_XML_FUNCTION,
                         Lists.of(streamRef, isReadonly), pos);
-            } else if (TypeTags.isStringTypeTag(refType.tag)) {
+            } else if (TypeTags.isStringTypeTag(safeType.tag)) {
                 result = getStreamFunctionVariableRef(queryBlock, QUERY_TO_STRING_FUNCTION, Lists.of(streamRef), pos);
             } else {
                 BType arrayType = refType;

compiler/ballerina-lang/src/main/java/org/wso2/ballerinalang/compiler/semantics/analyzer/QueryTypeChecker.java

@@ -323,13 +323,20 @@ void solveSelectTypeAndResolveType(BLangQueryExpr queryExpr, BLangExpression sel
                 resolvedType = getResolvedType(selectType, type, isReadonly, env);
                 break;
             case TypeTags.STRING:
+                selectType = checkExpr(selectExp, env, type, data);
+                resolvedType = symTable.stringType;
+                break;
             case TypeTags.XML:
             case TypeTags.XML_COMMENT:
             case TypeTags.XML_ELEMENT:
             case TypeTags.XML_PI:
             case TypeTags.XML_TEXT:
                 selectType = checkExpr(selectExp, env, type, data);
-                resolvedType = selectType;
+                if (types.isAssignable(selectType, symTable.xmlType)) {
+                    resolvedType = getResolvedType(new BXMLType(selectType, null), type, isReadonly, env);
+                } else {
+                    resolvedType = selectType;
+                }
                 break;
             case TypeTags.INTERSECTION:
                 type = ((BIntersectionType) type).effectiveType;

tests/jballerina-unit-test/src/test/java/org/ballerinalang/test/query/StringQueryExpressionTest.java

@@ -33,11 +33,12 @@
  */
 public class StringQueryExpressionTest {
 
-    private CompileResult result;
+    private CompileResult result, negativeResult;
 
     @BeforeClass
     public void setup() {
         result = BCompileUtil.compile("test-src/query/string-query-expression.bal");
+        negativeResult = BCompileUtil.compile("test-src/query/string-query-expression-negative.bal");
     }
 
     @Test(description = "Test simple query expression with string result")
@@ -48,6 +49,11 @@ public void testSimpleQueryExprForStringResult() {
         Assert.assertEquals(returnValues.toString(), "Alex Ranjan John ");
     }
 
+    @Test(description = "Test simple query expression with string result")
+    public void testSimpleQueryExprForStringResult2() {
+        BRunUtil.invoke(result, "testSimpleQueryExprForStringResult2");
+    }
+
     @Test(description = "Test query expression with where giving string result")
     public void testQueryExprWithWhereForStringResult() {
         Object returnValues = BRunUtil.invoke(result, "testQueryExprWithWhereForStringResult");
@@ -172,6 +178,15 @@ public void testQueryExprWithLimitForStringResultV2() {
         Assert.assertEquals(returnValues.toString(), "Ranjan John ");
     }
 
+    // issue - #40012
+    // @Test(description = "Negative Query expr for String tests")
+    // public void testNegativeQueryExprForXML() {
+    //     int index = 0;
+    //     validateError(negativeResult, index++, "ambiguous type '[string:Char, string:Char]'", 46, 16);
+    //     validateError(negativeResult, index++, "ambiguous type '[string:Char, string:Char, string:Char]'", 48, 16);
+    //     Assert.assertEquals(negativeResult.getErrorCount(), index);
+    // }
+
     @AfterClass
     public void tearDown() {
         result = null;

tests/jballerina-unit-test/src/test/java/org/ballerinalang/test/query/XMLQueryExpressionTest.java

@@ -71,7 +71,16 @@ public void testNegativeQueryExprForXML() {
         validateError(negativeResult, index++,
                 "incompatible types: expected 'xml<(xml:ProcessingInstruction & readonly)> & readonly', " +
                 "found 'xml:ProcessingInstruction'", 51, 16);
-        Assert.assertEquals(negativeResult.getErrorCount(), index);
+        validateError(negativeResult, index++,
+                "incompatible types: expected '(xml:Element|error)', found '(xml<xml:Element>|error)'", 81, 27);
+        // issue - #40012
+        // validateError(negativeResult, index++,
+        //         "ambiguous type '[xml:Element, xml:Element]'", 88, 16);
+        // validateError(negativeResult, index++,
+        //         "incompatible types: expected 'xml:Text', found 'xml:Element'", 94, 16);
+        // validateError(negativeResult, index++,
+        //         "ambiguous type '[xml:Element, xml:Element]'", 99, 16);
+        Assert.assertEquals(negativeResult.getErrorCount(), index + 3);
     }
 
     @Test(description = "Test simple query expression for XMLs - #1")
@@ -101,6 +110,11 @@ public void testSimpleQueryExprForXML3() {
                 "<price>30.00</price><price>29.99</price><price>49.99</price><price>39.95</price>");
     }
 
+    @Test(description = "Test simple query expression for XMLs - #4")
+    public void testSimpleQueryExprForXML4() {
+        BRunUtil.invoke(result, "testSimpleQueryExprForXML4");
+    }
+
     @Test(description = "Test simple query expression with limit clause for XMLs")
     public void testQueryExprWithLimitForXML() {
         Object returnValues = BRunUtil.invoke(result, "testQueryExprWithLimitForXML");

tests/jballerina-unit-test/src/test/resources/test-src/query/string-query-expression-negative.bal

@@ -0,0 +1,49 @@
+// Copyright (c) 2023 WSO2 Inc. (http://www.wso2.org) All Rights Reserved.
+//
+// WSO2 Inc. 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.
+
+type Book record {|
+    string title;
+    string author;
+|};
+
+class BookGenerator {
+    int i = 0;
+
+    public isolated function next() returns record {|Book value;|}|error? {
+        self.i += 1;
+        if (self.i < 0) {
+            return error("Error");
+        } else if (self.i >= 3) {
+            return ();
+        }
+        return {
+            value: {
+                title: "Title " + self.i.toString(), author: "Author " + self.i.toString()
+            }
+        };
+    }
+}
+
+function testSimpleQueryExprForStringNegative() returns error? {
+    string:Char chr = "a";
+    BookGenerator bookGenerator = new ();
+    stream<Book, error?> bookStream = new (bookGenerator);
+
+    string:Char[]|string _ = check from Book _ in bookStream
+        select chr;
+    string:Char[]|int|string _ = check from Book _ in bookStream
+        select chr;
+}

tests/jballerina-unit-test/src/test/resources/test-src/query/string-query-expression.bal

@@ -41,13 +41,77 @@ function testSimpleQueryExprForStringResult() returns string {
     return outputNameString;
 }
 
+type Book record {|
+    string title;
+    string author;
+|};
+
+class BookGenerator {
+    int i = 0;
+
+    public isolated function next() returns record {|Book value;|}|error? {
+        self.i += 1;
+        if (self.i < 0) {
+            return error("Error");
+        } else if (self.i >= 3) {
+            return ();
+        }
+        return {
+            value: {
+                title: "Title " + self.i.toString(), author: "Author " + self.i.toString()
+            }
+        };
+    }
+}
+
+function testSimpleQueryExprForStringResult2() {
+    error? e = trap simpleQueryExprForStringResult();
+    assertFalse(e is error);
+
+    e = trap simpleQueryExprForStringResult2();
+    assertFalse(e is error);
+
+    e = trap simpleQueryExprForStringResult3();
+    assertFalse(e is error);
+}
+
+function simpleQueryExprForStringResult() returns error? {
+    string:Char chr = "a";
+    BookGenerator bookGenerator = new ();
+    stream<Book, error?> bookStream = new (bookGenerator);
+    string strValue = check from Book _ in bookStream
+        select chr;
+    string expectedValue = "aa";
+    assertTrue(strValue is string);
+    assertEquality(strValue, expectedValue);
+}
+
+function simpleQueryExprForStringResult2() returns error? {
+    stream<Book, error?> bookStream = [{ author: "Author 1", title: "Title 1" },
+                                        {author: "Author 2", title: "Title 2" }].toStream();
+    string strValue = check from Book _ in bookStream
+        select <string:Char> "a";
+    string expectedValue = "aa";
+    assertTrue(strValue is string);
+    assertEquality(strValue, expectedValue);
+}
+
+function simpleQueryExprForStringResult3() returns error? {
+    string:Char chr = "a";
+    BookGenerator bookGenerator = new ();
+    stream<Book, error?> bookStream = new (bookGenerator);
+    string:Char[] strValue = check from Book _ in bookStream
+        select chr;
+    assertTrue(strValue is string:Char[]);
+    assertEquality(strValue[0], chr);
+    assertEquality(strValue[1], chr);
+}
+
 function testQueryExprWithWhereForStringResult() returns string {
     Person p1 = {firstName: "Alex", lastName: "George", age: 23};
     Person p2 = {firstName: "Ranjan", lastName: "Fonseka", age: 30};
     Person p3 = {firstName: "John", lastName: "David", age: 33};
-
     Person[] personList = [p1, p2, p3];
-
     string outputNameString =
                 from var person in personList
                 where person.age >= 30
@@ -336,3 +400,25 @@ function testQueryExprWithLimitForStringResultV2() returns string {
 
    return outputNameString;
 }
+
+function assertEquality(any|error actual, any|error expected) {
+    if expected is anydata && actual is anydata && expected == actual {
+        return;
+    }
+
+    if expected === actual {
+        return;
+    }
+
+    string expectedValAsString = expected is error ? expected.toString() : expected.toString();
+    string actualValAsString = actual is error ? actual.toString() : actual.toString();
+    panic error("expected '" + expectedValAsString + "', found '" + actualValAsString + "'");
+}
+
+function assertTrue(any|error actual) {
+    assertEquality(actual, true);
+}
+
+function assertFalse(any|error actual) {
+    assertEquality(actual, false);
+}

tests/jballerina-unit-test/src/test/resources/test-src/query/xml-query-expression-negative.bal

@@ -50,3 +50,54 @@ function testSimpleQueryExprForXMLWithReadonly1() {
     xml<xml:ProcessingInstruction> & readonly _ = from xml:ProcessingInstruction x in processingInstructions
         select x;
 }
+
+type Book record {|
+    string title;
+    string author;
+|};
+
+class BookGenerator {
+    int i = 0;
+
+    public isolated function next() returns record {|Book value;|}|error? {
+        self.i += 1;
+        if (self.i < 0) {
+            return error("Error");
+        } else if (self.i >= 3) {
+            return ();
+        }
+        return {
+            value: {
+                title: "Title " + self.i.toString(), author: "Author " + self.i.toString()
+            }
+        };
+    }
+}
+
+BookGenerator bookGenerator = new ();
+stream<Book, error?> bookStream = new (bookGenerator);
+
+function testSimpleQueryExprForXML() {
+    xml:Element _ = check from Book book in bookStream
+        select xml `<Book>
+                        <Author>${book.author}</Author>
+                        <Title>${book.title}</Title>
+                    </Book>`;
+
+    xml:Element|xml _ = check from Book book in bookStream
+        select xml `<Book>
+                        <Author>${book.author}</Author>
+                        <Title>${book.title}</Title>
+                    </Book>`;
+
+    xml:Text|xml _ = check from Book book in bookStream
+        select xml `<Book>
+                        <Author>${book.author}</Author>
+                        <Title>${book.title}</Title>
+                    </Book>`;
+    xml:Element[]|xml _ = check from Book book in bookStream
+        select xml `<Book>
+                        <Author>${book.author}</Author>
+                        <Title>${book.title}</Title>
+                    </Book>`;
+}