[core] Initial implementation of a validation framework in core

modules/openapi-generator-core/pom.xml

@@ -13,4 +13,11 @@
   <artifactId>openapi-generator-core</artifactId>
   <name>openapi-generator-core</name>
   <url>https://github.com/openapitools/openapi-generator</url>
+  <dependencies>
+    <dependency>
+      <groupId>org.testng</groupId>
+      <artifactId>testng</artifactId>
+      <scope>test</scope>
+    </dependency>
+  </dependencies>
 </project>

modules/openapi-generator-core/src/main/java/org/openapitools/codegen/validation/GenericValidator.java

@@ -0,0 +1,61 @@
+/*
+ * Copyright 2019 OpenAPI-Generator Contributors (https://openapi-generator.tech)
+ *
+ * Licensed 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.
+ */
+
+package org.openapitools.codegen.validation;
+
+import java.util.List;
+
+/**
+ * A generic implementation of a validator instance which simply applies rules to an input instance.
+ *
+ * @param <TInput> The type of object being evaluated.
+ */
+@SuppressWarnings({"WeakerAccess"})
+public class GenericValidator<TInput> implements Validator<TInput> {
+    private List<ValidationRule> rules;
+
+    /**
+     * Constructs a new instance of {@link GenericValidator}.
+     *
+     * @param rules The rules to be evaluated during validation.
+     */
+    public GenericValidator(List<ValidationRule> rules) {
+        this.rules = rules;
+    }
+
+    /**
+     * Validates input, resulting in a instance of {@link ValidationResult} which provides details on all validations performed (success, error, warning).
+     *
+     * @param input The object instance to be validated.
+     *
+     * @return A {@link ValidationResult} which details the success, error, and warning validation results.
+     */
+    @Override
+    public ValidationResult validate(TInput input) {
+        ValidationResult result = new ValidationResult();
+        if (rules != null) {
+            rules.forEach(it -> {
+                boolean passes = it.evaluate(input);
+                if (passes) {
+                    result.addResult(Validated.valid(it));
+                } else {
+                    result.addResult(Validated.invalid(it, it.getFailureMessage()));
+                }
+            });
+        }
+        return result;
+    }
+}

modules/openapi-generator-core/src/main/java/org/openapitools/codegen/validation/Invalid.java

@@ -0,0 +1,57 @@
+/*
+ * Copyright 2019 OpenAPI-Generator Contributors (https://openapi-generator.tech)
+ *
+ * Licensed 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.
+ */
+
+package org.openapitools.codegen.validation;
+
+/**
+ * Represents a {@link Validated} state which is "Invalid" to some degree of {@link Severity}.
+ */
+@SuppressWarnings({"WeakerAccess"})
+public final class Invalid extends Validated {
+    private String message;
+    private ValidationRule rule;
+
+    /**
+     * Constructs a new {@link Invalid} instance.
+     *
+     * @param rule The rule which was evaluated and resulted in this state.
+     * @param message The message to be displayed for this invalid state.
+     */
+    Invalid(ValidationRule rule, String message) {
+        this.rule = rule;
+        this.message = message;
+    }
+
+    @Override
+    String getMessage() {
+        return message;
+    }
+
+    @Override
+    ValidationRule getRule() {
+        return rule;
+    }
+
+    /**
+     * Get details about the severity of this invalid state.
+     * For instance, is this an {@link Severity#ERROR} or simply a {@link Severity#WARNING}.
+     *
+     * @return The {@link Severity} enum detailing this state's severity.
+     */
+    public Severity getSeverity() {
+        return rule.getSeverity();
+    }
+}

modules/openapi-generator-core/src/main/java/org/openapitools/codegen/validation/Severity.java

@@ -0,0 +1,33 @@
+/*
+ * Copyright 2019 OpenAPI-Generator Contributors (https://openapi-generator.tech)
+ *
+ * Licensed 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.
+ */
+
+package org.openapitools.codegen.validation;
+
+/**
+ * Defines different levels of severity to be used during validation.
+ */
+public enum Severity {
+    /**
+     * Lower severity indicating that the target state may be unpredictable, no longer supported, or known to have issues.
+     * Marking a type with this value should not result in application exceptions under normal operating circumstances.
+     */
+    WARNING,
+    /**
+     * Higher severity indicating that the target state is not supported, or is known to cause problems with the application.
+     * Marking a type with this value should result in an application exception or error exit code under normal operating circumstances.
+     */
+    ERROR
+}

modules/openapi-generator-core/src/main/java/org/openapitools/codegen/validation/Valid.java

@@ -0,0 +1,53 @@
+/*
+ * Copyright 2019 OpenAPI-Generator Contributors (https://openapi-generator.tech)
+ *
+ * Licensed 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.
+ */
+
+package org.openapitools.codegen.validation;
+
+/**
+ * Represents a {@link Validated} state which is "valid" according to the defined rule.
+ */
+public final class Valid extends Validated {
+    private ValidationRule rule;
+
+    /**
+     * Defines whether or not the validation resulted in a "valid" condition.
+     *
+     * @return <code>true</code> if the instance passed validation of the rule returned by {@link Validated#getRule()}.
+     */
+    @Override
+    boolean isValid() {
+        return true;
+    }
+
+    /**
+     * Constructs a new {@link Valid} instance.
+     *
+     * @param rule The rule which was evaluated and resulted in this state.
+     */
+    Valid(ValidationRule rule) {
+        this.rule = rule;
+    }
+
+    @Override
+    public String getMessage() {
+        return null;
+    }
+
+    @Override
+    public ValidationRule getRule() {
+        return rule;
+    }
+}

modules/openapi-generator-core/src/main/java/org/openapitools/codegen/validation/Validated.java

@@ -0,0 +1,68 @@
+/*
+ * Copyright 2019 OpenAPI-Generator Contributors (https://openapi-generator.tech)
+ *
+ * Licensed 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.
+ */
+
+package org.openapitools.codegen.validation;
+
+/**
+ * Provides details about the state of a completed validation.
+ */
+public abstract class Validated {
+    /**
+     * Defines whether or not the validation resulted in a "valid" condition.
+     *
+     * @return <code>true</code> if the instance passed validation of the rule returned by {@link Validated#getRule()}.
+     */
+    boolean isValid() {
+        return false;
+    }
+
+    /**
+     * Gets the rule which was evaluated and resulted in this state.
+     *
+     * @return The instance of {@link ValidationRule} which was evaluated.
+     */
+    abstract ValidationRule getRule();
+
+    /**
+     * Gets the message with details about this validated state.
+     *
+     * @return A string intended to be displayed to a user.
+     */
+    abstract String getMessage();
+
+    /**
+     * Creates an instance of an {@link Invalid} validation state.
+     *
+     * @param rule The rule which was evaluated.
+     * @param message The message to display to a user.
+     *
+     * @return A {@link Validated} instance representing an invalid state according to the rule.
+     */
+    public static Validated invalid(ValidationRule rule, String message) {
+        return new Invalid(rule, message);
+    }
+
+    /**
+     * Creates an instance of an {@link Valid} validation state.
+     *
+     * @param rule The rule which was evaluated.
+     *
+     * @return A {@link Validated} instance representing a valid state according to the rule.
+     */
+    public static Validated valid(ValidationRule rule) {
+        return new Valid(rule);
+    }
+}

modules/openapi-generator-core/src/main/java/org/openapitools/codegen/validation/ValidationResult.java

@@ -0,0 +1,104 @@
+/*
+ * Copyright 2019 OpenAPI-Generator Contributors (https://openapi-generator.tech)
+ *
+ * Licensed 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.
+ */
+
+package org.openapitools.codegen.validation;
+
+import java.util.ArrayList;
+import java.util.Collections;
+import java.util.List;
+import java.util.stream.Collectors;
+
+/**
+ * Encapsulates details about the result of a validation test.
+ */
+@SuppressWarnings("WeakerAccess")
+public final class ValidationResult {
+    private final List<Validated> validations;
+
+    /**
+     * Constructs a new {@link ValidationResult} instance, backed by the provided validations (useful for testing).
+     *
+     * @param validations A pre-defined set of validations to begin with.
+     */
+    private ValidationResult(List<Validated> validations) {
+        this.validations = Collections.synchronizedList(validations);
+    }
+
+    /**
+     * Constructs a new {@link ValidationResult} instance.
+     */
+    public ValidationResult() {
+        this(new ArrayList<>());
+    }
+
+    /**
+     * Gets all the validated states resulting from the evaluation. This includes all {@link Valid} and {@link Invalid} instances.
+     *
+     * @return All validated results.
+     */
+    public List<Validated> getAll() {
+        return  validations;
+    }
+
+    /**
+     * Gets a filtered list of {@link Valid} states.
+     *
+     * @return A list containing only {@link Valid} states.
+     */
+    public List<Valid> getValid(){
+        return validations.stream().filter(Validated::isValid).map(it -> (Valid)it).collect(Collectors.toList());
+    }
+
+    /**
+     * Gets a filters list of {@link Invalid} states with the level of {@link Severity#ERROR}
+     *
+     * @return A list of all validation errors.
+     */
+    public List<Invalid> getErrors(){
+        return validations.stream()
+                .filter(it -> !it.isValid())
+                .map(it -> (Invalid)it)
+                .filter(it -> it.getSeverity().equals(Severity.ERROR))
+                .collect(Collectors.toList());
+    }
+
+    /**
+     * Gets a filtered list of {@link Invalid} states with the level of {@link Severity#WARNING}
+     *
+     * @return A list of all validation warnings.
+     */
+    public List<Invalid> getWarnings(){
+        return validations.stream()
+                .filter(it -> !it.isValid())
+                .map(it -> (Invalid)it)
+                .filter(it -> it.getSeverity().equals(Severity.WARNING))
+                .collect(Collectors.toList());
+    }
+
+    /**
+     * Adds a validation state to the final results.
+     *
+     * @param validated The {@link Valid} or {@link Invalid} instance to add to validations.
+     */
+    public void addResult(Validated validated) {
+        synchronized (validations) {
+            ValidationRule rule = validated.getRule();
+            if (rule != null && !rule.equals(ValidationRule.empty())) {
+                validations.add(validated);
+            }
+        }
+    }
+}