Update input param validation logic

Fixes: ballerina-platform/ballerina-library#1339

graphql-compiler-plugin-tests/src/test/java/io/ballerina/stdlib/graphql/compiler/CompilerPluginTest.java

@@ -91,6 +91,14 @@ public void testValidService6() {
         Assert.assertEquals(diagnosticResult.diagnostics().size(), 0);
     }
 
+    @Test
+    public void testValidService7() {
+        Package currentPackage = loadPackage("valid_service_7");
+        PackageCompilation compilation = currentPackage.getCompilation();
+        DiagnosticResult diagnosticResult = compilation.diagnosticResult();
+        Assert.assertEquals(diagnosticResult.diagnostics().size(), 0);
+    }
+
     @Test
     public void testInvalidService1() {
         Package currentPackage = loadPackage("invalid_service_1");
@@ -203,6 +211,19 @@ public void testInvalidService10() {
         }
     }
 
+    @Test
+    public void testInvalidService11() {
+        Package currentPackage = loadPackage("invalid_service_11");
+        PackageCompilation compilation = currentPackage.getCompilation();
+        DiagnosticResult diagnosticResult = compilation.diagnosticResult();
+        Assert.assertEquals(diagnosticResult.diagnostics().size(), 4);
+        Object[] diagnostics = diagnosticResult.diagnostics().toArray();
+        for (Object obj : diagnostics) {
+            Diagnostic diagnostic = (Diagnostic) obj;
+            assertDiagnostic(diagnostic, CompilationErrors.INVALID_RESOURCE_INPUT_PARAM);
+        }
+    }
+
     private Package loadPackage(String path) {
         Path projectDirPath = RESOURCE_DIRECTORY.resolve(path);
         BuildProject project = BuildProject.load(getEnvironmentBuilder(), projectDirPath);

graphql-compiler-plugin-tests/src/test/resources/ballerina_sources/invalid_service_11/Ballerina.toml

@@ -0,0 +1,4 @@
+[package]
+org = "graphql_test"
+name = "invalid_service_11"
+version = "0.1.0"

graphql-compiler-plugin-tests/src/test/resources/ballerina_sources/invalid_service_11/service.bal

@@ -0,0 +1,41 @@
+// Copyright (c) 2021 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.
+
+import ballerina/graphql;
+
+service graphql:Service on new graphql:Listener(4000) {
+    isolated resource function get greeting(int|string? something) returns string {
+        return "Hello";
+    }
+}
+
+service graphql:Service on new graphql:Listener(4000) {
+    isolated resource function get greet(json? name) returns string {
+        return "Hello";
+    }
+}
+
+service graphql:Service on new graphql:Listener(4000) {
+    isolated resource function get greet(map<string>? name) returns string {
+        return "Hello";
+    }
+}
+
+service graphql:Service on new graphql:Listener(4000) {
+    isolated resource function get greet(byte[]? name) returns string {
+        return "Hello";
+    }
+}

graphql-compiler-plugin-tests/src/test/resources/ballerina_sources/valid_service_7/Ballerina.toml

@@ -0,0 +1,4 @@
+[package]
+org = "graphql_test"
+name = "valid_service_7"
+version = "0.1.0"

graphql-compiler-plugin-tests/src/test/resources/ballerina_sources/valid_service_7/service.bal

@@ -0,0 +1,35 @@
+// Copyright (c) 2021 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.
+
+import ballerina/graphql;
+
+service graphql:Service on new graphql:Listener(4000) {
+    isolated resource function get birthdate(string? format) returns string {
+        return "01-01-1980";
+    }
+}
+
+service graphql:Service on new graphql:Listener(4000) {
+    isolated resource function get isLegal(int? age) returns boolean {
+        if (age is int) {
+            if (age < 21) {
+                return false;
+            }
+            return true;
+        }
+        return false;
+    }
+}

graphql-compiler-plugin/src/main/java/io/ballerina/stdlib/graphql/compiler/GraphqlFunctionValidator.java

@@ -174,14 +174,27 @@ private void validateInputParamType(FunctionDefinitionNode functionDefinitionNod
     }
 
     private boolean hasInvalidInputParamType(TypeSymbol inputTypeSymbol) {
+        if (inputTypeSymbol.typeKind() == TypeDescKind.UNION) {
+            List<TypeSymbol> members = ((UnionTypeSymbol) inputTypeSymbol).memberTypeDescriptors();
+            boolean hasInvalidMember = false;
+            int hasType = 0;
+            for (TypeSymbol member: members) {
+                if (member.typeKind() != TypeDescKind.NIL) {
+                    hasInvalidMember = hasInvalidInputParamType(member);
+                    hasType++;
+                }
+            }
+            if (hasType > 1) {
+                hasInvalidMember = true;
+            }
+            return hasInvalidMember;
+        }
         if (inputTypeSymbol.typeKind() == TypeDescKind.TYPE_REFERENCE) {
             if ((((TypeReferenceTypeSymbol) inputTypeSymbol).definition()).kind() == SymbolKind.ENUM) {
                 return false;
             }
-        } else {
-            return !hasPrimitiveType(inputTypeSymbol);
         }
-        return true;
+        return !hasPrimitiveType(inputTypeSymbol);
     }
 
     private boolean hasInvalidReturnType(TypeSymbol returnTypeSymbol) {