feat: validation for annotation target (#670)

Closes #543

### Summary of Changes

* Show an error if an annotation is called on an incorrect target
* Show a warning if the target list of an annotation has duplicate
entries

src/language/builtins/safe-ds-annotations.ts

@@ -1,25 +1,42 @@
-import { isSdsAnnotation, SdsAnnotatedObject, SdsAnnotation, SdsModule, SdsParameter } from '../generated/ast.js';
-import { getArguments, findFirstAnnotationCallOf, hasAnnotationCallOf } from '../helpers/nodeProperties.js';
+import {
+    isSdsAnnotation,
+    isSdsEnum,
+    SdsAnnotatedObject,
+    SdsAnnotation,
+    SdsEnumVariant,
+    SdsModule,
+    SdsParameter,
+} from '../generated/ast.js';
+import {
+    findFirstAnnotationCallOf,
+    getArguments,
+    getEnumVariants,
+    getParameters,
+    hasAnnotationCallOf,
+} from '../helpers/nodeProperties.js';
 import { SafeDsModuleMembers } from './safe-ds-module-members.js';
 import { resourceNameToUri } from '../../helpers/resources.js';
-import { URI } from 'langium';
+import { EMPTY_STREAM, getContainerOfType, Stream, stream, URI } from 'langium';
 import { SafeDsServices } from '../safe-ds-module.js';
 import { SafeDsNodeMapper } from '../helpers/safe-ds-node-mapper.js';
-import { EvaluatedNode, StringConstant } from '../partialEvaluation/model.js';
+import { EvaluatedEnumVariant, EvaluatedList, EvaluatedNode, StringConstant } from '../partialEvaluation/model.js';
 import { SafeDsPartialEvaluator } from '../partialEvaluation/safe-ds-partial-evaluator.js';
+import { SafeDsEnums } from './safe-ds-enums.js';
 
 const ANNOTATION_USAGE_URI = resourceNameToUri('builtins/safeds/lang/annotationUsage.sdsstub');
 const CODE_GENERATION_URI = resourceNameToUri('builtins/safeds/lang/codeGeneration.sdsstub');
 const IDE_INTEGRATION_URI = resourceNameToUri('builtins/safeds/lang/ideIntegration.sdsstub');
 const MATURITY_URI = resourceNameToUri('builtins/safeds/lang/maturity.sdsstub');
 
 export class SafeDsAnnotations extends SafeDsModuleMembers<SdsAnnotation> {
+    private readonly builtinEnums: SafeDsEnums;
     private readonly nodeMapper: SafeDsNodeMapper;
     private readonly partialEvaluator: SafeDsPartialEvaluator;
 
     constructor(services: SafeDsServices) {
         super(services);
 
+        this.builtinEnums = services.builtins.Enums;
         this.nodeMapper = services.helpers.NodeMapper;
         this.partialEvaluator = services.evaluation.PartialEvaluator;
     }
@@ -82,6 +99,32 @@ export class SafeDsAnnotations extends SafeDsModuleMembers<SdsAnnotation> {
         return this.getAnnotation(ANNOTATION_USAGE_URI, 'Repeatable');
     }
 
+    streamValidTargets(node: SdsAnnotation | undefined): Stream<SdsEnumVariant> {
+        // If no targets are specified, every target is valid
+        if (!hasAnnotationCallOf(node, this.Target)) {
+            return stream(getEnumVariants(this.builtinEnums.AnnotationTarget));
+        }
+
+        // If targets are specified, but we could not evaluate them to a list, no target is valid
+        const value = this.getArgumentValue(node, this.Target, 'targets');
+        if (!(value instanceof EvaluatedList)) {
+            return EMPTY_STREAM;
+        }
+
+        // Otherwise, filter the elements of the list and keep only variants of the AnnotationTarget enum
+        return stream(value.elements)
+            .filter(
+                (it) =>
+                    it instanceof EvaluatedEnumVariant &&
+                    getContainerOfType(it.variant, isSdsEnum) === this.builtinEnums.AnnotationTarget,
+            )
+            .map((it) => (<EvaluatedEnumVariant>it).variant);
+    }
+
+    get Target(): SdsAnnotation | undefined {
+        return this.getAnnotation(ANNOTATION_USAGE_URI, 'Target');
+    }
+
     private getAnnotation(uri: URI, name: string): SdsAnnotation | undefined {
         return this.getModuleMember(uri, name, isSdsAnnotation);
     }
@@ -96,9 +139,17 @@ export class SafeDsAnnotations extends SafeDsModuleMembers<SdsAnnotation> {
         parameterName: string,
     ): EvaluatedNode {
         const annotationCall = findFirstAnnotationCallOf(node, annotation);
-        const argumentValue = getArguments(annotationCall).find(
+
+        // Parameter is set explicitly
+        const argument = getArguments(annotationCall).find(
             (it) => this.nodeMapper.argumentToParameter(it)?.name === parameterName,
-        )?.value;
-        return this.partialEvaluator.evaluate(argumentValue);
+        );
+        if (argument) {
+            return this.partialEvaluator.evaluate(argument.value);
+        }
+
+        // Parameter is not set explicitly, so we use the default value
+        const parameter = getParameters(annotation).find((it) => it.name === parameterName);
+        return this.partialEvaluator.evaluate(parameter?.defaultValue);
     }
 }

src/language/builtins/safe-ds-enums.ts

@@ -0,0 +1,16 @@
+import { isSdsEnum, SdsEnum } from '../generated/ast.js';
+import { SafeDsModuleMembers } from './safe-ds-module-members.js';
+import { resourceNameToUri } from '../../helpers/resources.js';
+import { URI } from 'langium';
+
+const ANNOTATION_USAGE_URI = resourceNameToUri('builtins/safeds/lang/annotationUsage.sdsstub');
+
+export class SafeDsEnums extends SafeDsModuleMembers<SdsEnum> {
+    get AnnotationTarget(): SdsEnum | undefined {
+        return this.getEnum(ANNOTATION_USAGE_URI, 'AnnotationTarget');
+    }
+
+    private getEnum(uri: URI, name: string): SdsEnum | undefined {
+        return this.getModuleMember(uri, name, isSdsEnum);
+    }
+}

src/language/helpers/nodeProperties.ts

@@ -153,6 +153,10 @@ export const getAnnotationCalls = (node: SdsAnnotatedObject | undefined): SdsAnn
     }
 };
 
+export const getAnnotationCallTarget = (node: SdsAnnotationCall | undefined): SdsDeclaration | undefined => {
+    return getContainerOfType(node, isSdsDeclaration);
+};
+
 export const findFirstAnnotationCallOf = (
     node: SdsAnnotatedObject | undefined,
     expected: SdsAnnotation | undefined,

src/language/safe-ds-module.ts

@@ -29,6 +29,7 @@ import { SafeDsCoreTypes } from './typing/safe-ds-core-types.js';
 import { SafeDsNodeKindProvider } from './lsp/safe-ds-node-kind-provider.js';
 import { SafeDsDocumentSymbolProvider } from './lsp/safe-ds-document-symbol-provider.js';
 import { SafeDsDocumentBuilder } from './workspace/safe-ds-document-builder.js';
+import { SafeDsEnums } from './builtins/safe-ds-enums.js';
 
 /**
  * Declaration of custom services - add your own service classes here.
@@ -37,6 +38,7 @@ export type SafeDsAddedServices = {
     builtins: {
         Annotations: SafeDsAnnotations;
         Classes: SafeDsClasses;
+        Enums: SafeDsEnums;
     };
     evaluation: {
         PartialEvaluator: SafeDsPartialEvaluator;
@@ -70,6 +72,7 @@ export const SafeDsModule: Module<SafeDsServices, PartialLangiumServices & SafeD
     builtins: {
         Annotations: (services) => new SafeDsAnnotations(services),
         Classes: (services) => new SafeDsClasses(services),
+        Enums: (services) => new SafeDsEnums(services),
     },
     evaluation: {
         PartialEvaluator: (services) => new SafeDsPartialEvaluator(services),

src/language/validation/builtins/target.ts

@@ -0,0 +1,156 @@
+import { ValidationAcceptor } from 'langium';
+import {
+    isSdsAnnotation,
+    isSdsAttribute,
+    isSdsClass,
+    isSdsEnum,
+    isSdsEnumVariant,
+    isSdsFunction,
+    isSdsModule,
+    isSdsParameter,
+    isSdsPipeline,
+    isSdsResult,
+    isSdsSegment,
+    isSdsTypeParameter,
+    SdsAnnotation,
+    SdsAnnotationCall,
+} from '../../generated/ast.js';
+import { SafeDsServices } from '../../safe-ds-module.js';
+import { duplicatesBy, isEmpty } from '../../../helpers/collectionUtils.js';
+import { pluralize } from '../../../helpers/stringUtils.js';
+import { findFirstAnnotationCallOf, getAnnotationCallTarget } from '../../helpers/nodeProperties.js';
+
+export const CODE_TARGET_DUPLICATE_TARGET = 'target/duplicate-target';
+export const CODE_TARGET_WRONG_TARGET = 'target/wrong-target';
+
+export const targetShouldNotHaveDuplicateEntries = (services: SafeDsServices) => {
+    const builtinAnnotations = services.builtins.Annotations;
+
+    return (node: SdsAnnotation, accept: ValidationAcceptor) => {
+        const annotationCall = findFirstAnnotationCallOf(node, builtinAnnotations.Target);
+        if (!annotationCall) {
+            return;
+        }
+
+        const validTargets = builtinAnnotations.streamValidTargets(node).map((it) => `'${it.name}'`);
+        const duplicateTargets = duplicatesBy(validTargets, (it) => it)
+            .distinct()
+            .toArray();
+
+        if (isEmpty(duplicateTargets)) {
+            return;
+        }
+
+        const noun = pluralize(duplicateTargets.length, 'target');
+        const duplicateTargetString = duplicateTargets.join(', ');
+        const verb = pluralize(duplicateTargets.length, 'occurs', 'occur');
+
+        accept('warning', `The ${noun} ${duplicateTargetString} ${verb} multiple times.`, {
+            node: annotationCall,
+            property: 'annotation',
+            code: CODE_TARGET_DUPLICATE_TARGET,
+        });
+    };
+};
+
+export const annotationCallMustHaveCorrectTarget = (services: SafeDsServices) => {
+    const builtinAnnotations = services.builtins.Annotations;
+
+    return (node: SdsAnnotationCall, accept: ValidationAcceptor) => {
+        const annotation = node.annotation?.ref;
+        if (!annotation) {
+            return;
+        }
+
+        const actualTarget = getActualTarget(node);
+        /* c8 ignore start */
+        if (!actualTarget) {
+            return;
+        }
+        /* c8 ignore stop */
+
+        const validTargets = builtinAnnotations
+            .streamValidTargets(annotation)
+            .map((it) => it.name)
+            .toSet();
+
+        if (!validTargets.has(actualTarget.enumVariantName)) {
+            accept('error', `The annotation '${annotation.name}' cannot be applied to ${actualTarget.prettyName}.`, {
+                node,
+                property: 'annotation',
+                code: CODE_TARGET_WRONG_TARGET,
+            });
+        }
+    };
+};
+
+const getActualTarget = (node: SdsAnnotationCall): GetActualTargetResult | void => {
+    const annotatedObject = getAnnotationCallTarget(node);
+
+    if (isSdsAnnotation(annotatedObject)) {
+        return {
+            enumVariantName: 'Annotation',
+            prettyName: 'an annotation',
+        };
+    } else if (isSdsAttribute(annotatedObject)) {
+        return {
+            enumVariantName: 'Attribute',
+            prettyName: 'an attribute',
+        };
+    } else if (isSdsClass(annotatedObject)) {
+        return {
+            enumVariantName: 'Class',
+            prettyName: 'a class',
+        };
+    } else if (isSdsEnum(annotatedObject)) {
+        return {
+            enumVariantName: 'Enum',
+            prettyName: 'an enum',
+        };
+    } else if (isSdsEnumVariant(annotatedObject)) {
+        return {
+            enumVariantName: 'EnumVariant',
+            prettyName: 'an enum variant',
+        };
+    } else if (isSdsFunction(annotatedObject)) {
+        return {
+            enumVariantName: 'Function',
+            prettyName: 'a function',
+        };
+    } else if (isSdsModule(annotatedObject)) {
+        return {
+            enumVariantName: 'Module',
+            prettyName: 'a module',
+        };
+    } else if (isSdsParameter(annotatedObject)) {
+        return {
+            enumVariantName: 'Parameter',
+            prettyName: 'a parameter',
+        };
+    } else if (isSdsPipeline(annotatedObject)) {
+        return {
+            enumVariantName: 'Pipeline',
+            prettyName: 'a pipeline',
+        };
+    } else if (isSdsResult(annotatedObject)) {
+        return {
+            enumVariantName: 'Result',
+            prettyName: 'a result',
+        };
+    } else if (isSdsSegment(annotatedObject)) {
+        return {
+            enumVariantName: 'Segment',
+            prettyName: 'a segment',
+        };
+    } else if (isSdsTypeParameter(annotatedObject)) {
+        return {
+            enumVariantName: 'TypeParameter',
+            prettyName: 'a type parameter',
+        };
+    }
+};
+
+interface GetActualTargetResult {
+    enumVariantName: string;
+    prettyName: string;
+}

src/language/validation/safe-ds-validator.ts

@@ -126,6 +126,7 @@ import {
     literalTypeMustNotContainMapLiteral,
     literalTypeShouldNotHaveDuplicateLiteral,
 } from './other/types/literalTypes.js';
+import { annotationCallMustHaveCorrectTarget, targetShouldNotHaveDuplicateEntries } from './builtins/target.js';
 
 /**
  * Register custom validation checks.
@@ -150,12 +151,14 @@ export const registerValidationChecks = function (services: SafeDsServices) {
             annotationMustContainUniqueNames,
             annotationParameterListShouldNotBeEmpty,
             annotationParameterShouldNotHaveConstModifier,
+            targetShouldNotHaveDuplicateEntries(services),
         ],
         SdsAnnotationCall: [
             annotationCallAnnotationShouldNotBeDeprecated(services),
             annotationCallAnnotationShouldNotBeExperimental(services),
             annotationCallArgumentListShouldBeNeeded,
             annotationCallArgumentsMustBeConstant(services),
+            annotationCallMustHaveCorrectTarget(services),
             annotationCallMustNotLackArgumentList,
         ],
         SdsArgument: [