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Allow empty layers in LayeredArchitecture & OnionArchitecture when co…
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…nfigured #273

Resolves #267 & #271:

After #177 had prevented empty layers by default, this can now be overridden to re-allow empty layers in `LayeredArchitecture` & `OnionArchitecture`.
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@codecholeric
codecholeric authored Jan 9, 2020
2 parents 0049043 + 92307b7 commit 1bd11d7
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Showing 2 changed files with 172 additions and 27 deletions.
90 changes: 73 additions & 17 deletions archunit/src/main/java/com/tngtech/archunit/library/Architectures.java
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Original file line number Diff line number Diff line change
Expand Up @@ -69,7 +69,7 @@ private Architectures() {
/**
* Can be used to assert a typical layered architecture, e.g. with an UI layer, a business logic layer and
* a persistence layer, where specific access rules should be adhered to, like UI may not access persistence
* and each layer may only access lower layers, i.e. UI --> business logic --> persistence.
* and each layer may only access lower layers, i.e. UI → business logic → persistence.
* <br><br>
* A layered architecture can for example be defined like this:
* <pre><code>layeredArchitecture()
Expand All @@ -86,7 +86,7 @@ private Architectures() {
* layer 'Persistence' MAY NOT access layer 'Business Logic' AND MAY NOT access layer 'UI' (black list).<br>
* {@link LayeredArchitecture LayeredArchitecture} only supports the white list way, because it prevents detours "outside of
* the architecture", e.g.<br>
* 'Persistence' --&gt; 'my.application.somehelper' --&gt; 'Business Logic'<br>
* 'Persistence' &rarr; 'my.application.somehelper' &rarr; 'Business Logic'<br>
* The white list way enforces that every class that wants to interact with classes inside of
* the layered architecture must be part of the layered architecture itself and thus adhere to the same rules.
*
Expand All @@ -102,22 +102,39 @@ public static final class LayeredArchitecture implements ArchRule {
private final Set<LayerDependencySpecification> dependencySpecifications;
private final PredicateAggregator<Dependency> irrelevantDependenciesPredicate;
private final Optional<String> overriddenDescription;
private boolean optionalLayers;

private LayeredArchitecture() {
this(new LayerDefinitions(),
new LinkedHashSet<LayerDependencySpecification>(),
new PredicateAggregator<Dependency>().thatORs(),
Optional.<String>absent());
Optional.<String>absent(),
false);
}

private LayeredArchitecture(LayerDefinitions layerDefinitions,
Set<LayerDependencySpecification> dependencySpecifications,
PredicateAggregator<Dependency> irrelevantDependenciesPredicate,
Optional<String> overriddenDescription) {
Optional<String> overriddenDescription,
boolean optionalLayers) {
this.layerDefinitions = layerDefinitions;
this.dependencySpecifications = dependencySpecifications;
this.irrelevantDependenciesPredicate = irrelevantDependenciesPredicate;
this.overriddenDescription = overriddenDescription;
this.optionalLayers = optionalLayers;
}

/**
* By default, layers defined with {@link #layer(String)} must not be empty, i.e. contain at least one class.
* <br>
* <code>withOptionalLayers(true)</code> can be used to make all layers optional.<br>
* <code>withOptionalLayers(false)</code> still allows to define individual optional layers with {@link #optionalLayer(String)}.
* @see #optionalLayer(String)
*/
@PublicAPI(usage = ACCESS)
public LayeredArchitecture withOptionalLayers(boolean optionalLayers) {
this.optionalLayers = optionalLayers;
return this;
}

private LayeredArchitecture addLayerDefinition(LayerDefinition definition) {
Expand All @@ -130,9 +147,27 @@ private LayeredArchitecture addDependencySpecification(LayerDependencySpecificat
return this;
}

/**
* Starts the definition of a new layer within the current {@link #layeredArchitecture() LayeredArchitecture}.
* <br>
* Unless {@link #withOptionalLayers(boolean) withOptionalLayers(true}} is used, this layer must not be empty.
* @see #optionalLayer(String)
*/
@PublicAPI(usage = ACCESS)
public LayerDefinition layer(String name) {
return new LayerDefinition(name);
return new LayerDefinition(name, false);
}

/**
* Starts the definition of a new optional layer within the current {@link #layeredArchitecture() LayeredArchitecture}.
* <br>
* An optional layer will not fail if it is empty, i.e. does not contain any classes.
* When {@link #withOptionalLayers(boolean) withOptionalLayers(true)} is used, all layers are optional by default,
* such that there is no difference between {@link #optionalLayer(String)} and {@link #layer(String)} anymore
*/
@PublicAPI(usage = ACCESS)
public LayerDefinition optionalLayer(String name) {
return new LayerDefinition(name, true);
}

@Override
Expand All @@ -142,7 +177,7 @@ public String getDescription() {
return overriddenDescription.get();
}

List<String> lines = newArrayList("Layered architecture consisting of");
List<String> lines = newArrayList("Layered architecture consisting of" + (optionalLayers ? " (optional)" : ""));
for (LayerDefinition definition : layerDefinitions) {
lines.add(definition.toString());
}
Expand All @@ -161,15 +196,23 @@ public String toString() {
@PublicAPI(usage = ACCESS)
public EvaluationResult evaluate(JavaClasses classes) {
EvaluationResult result = new EvaluationResult(this, Priority.MEDIUM);
for (LayerDefinition layerDefinition : layerDefinitions) {
result.add(evaluateLayersShouldNotBeEmpty(classes, layerDefinition));
}
checkEmptyLayers(classes, result);
for (LayerDependencySpecification specification : dependencySpecifications) {
result.add(evaluateDependenciesShouldBeSatisfied(classes, specification));
}
return result;
}

private void checkEmptyLayers(JavaClasses classes, EvaluationResult result) {
if (!optionalLayers) {
for (LayerDefinition layerDefinition : layerDefinitions) {
if (!layerDefinition.isOptional()) {
result.add(evaluateLayersShouldNotBeEmpty(classes, layerDefinition));
}
}
}
}

private EvaluationResult evaluateLayersShouldNotBeEmpty(JavaClasses classes, LayerDefinition layerDefinition) {
return classes().that(layerDefinitions.containsPredicateFor(layerDefinition.name))
.should(notBeEmptyFor(layerDefinition))
Expand Down Expand Up @@ -235,7 +278,7 @@ public ArchRule because(String reason) {
public LayeredArchitecture as(String newDescription) {
return new LayeredArchitecture(
layerDefinitions, dependencySpecifications,
irrelevantDependenciesPredicate, Optional.of(newDescription));
irrelevantDependenciesPredicate, Optional.of(newDescription), optionalLayers);
}

@PublicAPI(usage = ACCESS)
Expand All @@ -253,7 +296,7 @@ public LayeredArchitecture ignoreDependency(
DescribedPredicate<? super JavaClass> origin, DescribedPredicate<? super JavaClass> target) {
return new LayeredArchitecture(
layerDefinitions, dependencySpecifications,
irrelevantDependenciesPredicate.add(dependency(origin, target)), overriddenDescription);
irrelevantDependenciesPredicate.add(dependency(origin, target)), overriddenDescription, optionalLayers);
}

@PublicAPI(usage = ACCESS)
Expand Down Expand Up @@ -307,11 +350,13 @@ public Iterator<LayerDefinition> iterator() {

public final class LayerDefinition {
private final String name;
private final boolean optional;
private DescribedPredicate<JavaClass> containsPredicate;

private LayerDefinition(String name) {
private LayerDefinition(String name, boolean optional) {
checkState(!isNullOrEmpty(name), "Layer name must be present");
this.name = name;
this.optional = optional;
}

@PublicAPI(usage = ACCESS)
Expand All @@ -327,13 +372,17 @@ public LayeredArchitecture definedBy(String... packageIdentifiers) {
return definedBy(resideInAnyPackage(packageIdentifiers).as(description));
}

boolean isOptional() {
return optional;
}

DescribedPredicate<JavaClass> containsPredicate() {
return containsPredicate;
}

@Override
public String toString() {
return String.format("layer '%s' (%s)", name, containsPredicate);
return String.format("%slayer '%s' (%s)", optional ? "optional " : "", name, containsPredicate);
}
}

Expand Down Expand Up @@ -379,12 +428,12 @@ public static final class OnionArchitecture implements ArchRule {
private static final String APPLICATION_SERVICE_LAYER = "application service";
private static final String ADAPTER_LAYER = "adapter";

private final Optional<String> overriddenDescription;
private String[] domainModelPackageIdentifiers = new String[0];
private String[] domainServicePackageIdentifiers = new String[0];
private String[] applicationPackageIdentifiers = new String[0];
private Map<String, String[]> adapterPackageIdentifiers = new LinkedHashMap<>();

private final Optional<String> overriddenDescription;
private boolean optionalLayers = false;

private OnionArchitecture() {
overriddenDescription = Optional.absent();
Expand Down Expand Up @@ -426,6 +475,12 @@ public OnionArchitecture adapter(String name, String... packageIdentifiers) {
return this;
}

@PublicAPI(usage = ACCESS)
public OnionArchitecture withOptionalLayers(boolean optionalLayers) {
this.optionalLayers = optionalLayers;
return this;
}

private LayeredArchitecture layeredArchitectureDelegate() {
LayeredArchitecture layeredArchitectureDelegate = layeredArchitecture()
.layer(DOMAIN_MODEL_LAYER).definedBy(domainModelPackageIdentifiers)
Expand All @@ -434,7 +489,8 @@ private LayeredArchitecture layeredArchitectureDelegate() {
.layer(ADAPTER_LAYER).definedBy(concatenateAll(adapterPackageIdentifiers.values()))
.whereLayer(DOMAIN_MODEL_LAYER).mayOnlyBeAccessedByLayers(DOMAIN_SERVICE_LAYER, APPLICATION_SERVICE_LAYER, ADAPTER_LAYER)
.whereLayer(DOMAIN_SERVICE_LAYER).mayOnlyBeAccessedByLayers(APPLICATION_SERVICE_LAYER, ADAPTER_LAYER)
.whereLayer(APPLICATION_SERVICE_LAYER).mayOnlyBeAccessedByLayers(ADAPTER_LAYER);
.whereLayer(APPLICATION_SERVICE_LAYER).mayOnlyBeAccessedByLayers(ADAPTER_LAYER)
.withOptionalLayers(optionalLayers);

for (Map.Entry<String, String[]> adapter : adapterPackageIdentifiers.entrySet()) {
String adapterLayer = getAdapterLayer(adapter.getKey());
Expand Down Expand Up @@ -484,7 +540,7 @@ public String getDescription() {
return overriddenDescription.get();
}

List<String> lines = newArrayList("Onion architecture consisting of");
List<String> lines = newArrayList("Onion architecture consisting of" + (optionalLayers ? " (optional)" : ""));
if (domainModelPackageIdentifiers.length > 0) {
lines.add(String.format("domain models ('%s')", Joiner.on("', '").join(domainModelPackageIdentifiers)));
}
Expand Down
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