add support for const keyword

core/pom.xml

@@ -118,6 +118,7 @@
                     -->
                     <include>**/tests/draft2020-12/additionalProperties.json</include>
                     <include>**/tests/draft2020-12/boolean_schema.json</include>
+                    <include>**/tests/draft2020-12/const.json</include>
                     <include>**/tests/draft2020-12/enum.json</include>
                     <include>**/tests/draft2020-12/exclusiveMaximum.json</include>
                     <include>**/tests/draft2020-12/exclusiveMinimum.json</include>

core/src/main/java/io/github/sebastiantoepfer/jsonschema/core/keyword/type/AnyKeywordType.java

@@ -0,0 +1,52 @@
+/*
+ * The MIT License
+ *
+ * Copyright 2024 sebastian.
+ *
+ * Permission is hereby granted, free of charge, to any person obtaining a copy
+ * of this software and associated documentation files (the "Software"), to deal
+ * in the Software without restriction, including without limitation the rights
+ * to use, copy, modify, merge, publish, distribute, sublicense, and/or sell
+ * copies of the Software, and to permit persons to whom the Software is
+ * furnished to do so, subject to the following conditions:
+ *
+ * The above copyright notice and this permission notice shall be included in
+ * all copies or substantial portions of the Software.
+ *
+ * THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
+ * IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
+ * FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
+ * AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
+ * LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
+ * OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN
+ * THE SOFTWARE.
+ */
+package io.github.sebastiantoepfer.jsonschema.core.keyword.type;
+
+import io.github.sebastiantoepfer.jsonschema.JsonSchema;
+import io.github.sebastiantoepfer.jsonschema.keyword.Keyword;
+import io.github.sebastiantoepfer.jsonschema.keyword.KeywordType;
+import jakarta.json.JsonValue;
+import java.util.Objects;
+import java.util.function.Function;
+
+public class AnyKeywordType implements KeywordType {
+
+    private final String name;
+    private final Function<JsonValue, Keyword> keywordCreator;
+
+    public AnyKeywordType(final String name, final Function<JsonValue, Keyword> keywordCreator) {
+        this.name = Objects.requireNonNull(name);
+        this.keywordCreator = Objects.requireNonNull(keywordCreator);
+    }
+
+    @Override
+    public String name() {
+        return name;
+    }
+
+    @Override
+    public Keyword createKeyword(final JsonSchema schema) {
+        return keywordCreator.apply(schema.asJsonObject().getOrDefault(name, JsonValue.NULL));
+    }
+}

core/src/main/java/io/github/sebastiantoepfer/jsonschema/core/vocab/validation/ConstKeyword.java

@@ -0,0 +1,84 @@
+/*
+ * The MIT License
+ *
+ * Copyright 2024 sebastian.
+ *
+ * Permission is hereby granted, free of charge, to any person obtaining a copy
+ * of this software and associated documentation files (the "Software"), to deal
+ * in the Software without restriction, including without limitation the rights
+ * to use, copy, modify, merge, publish, distribute, sublicense, and/or sell
+ * copies of the Software, and to permit persons to whom the Software is
+ * furnished to do so, subject to the following conditions:
+ *
+ * The above copyright notice and this permission notice shall be included in
+ * all copies or substantial portions of the Software.
+ *
+ * THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
+ * IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
+ * FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
+ * AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
+ * LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
+ * OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN
+ * THE SOFTWARE.
+ */
+package io.github.sebastiantoepfer.jsonschema.core.vocab.validation;
+
+import io.github.sebastiantoepfer.ddd.common.Media;
+import io.github.sebastiantoepfer.ddd.media.json.JsonObjectPrintable;
+import io.github.sebastiantoepfer.jsonschema.InstanceType;
+import io.github.sebastiantoepfer.jsonschema.keyword.Assertion;
+import jakarta.json.Json;
+import jakarta.json.JsonNumber;
+import jakarta.json.JsonValue;
+import java.util.Objects;
+
+/**
+ * <b>const</b> : <i>Any</i><br/>
+ * Validation succeeds if the instance is equal to this keyword’s value.<br/>
+ * <br/>
+ * <ul>
+ * <li>assertion</li>
+ * </ul>
+ *
+ * source: https://www.learnjsonschema.com/2020-12/validation/const/
+ * spec: https://json-schema.org/draft/2020-12/json-schema-validation.html#section-6.1.3
+ */
+class ConstKeyword implements Assertion {
+
+    static final String NAME = "const";
+    private final JsonValue allowedValue;
+
+    public ConstKeyword(final JsonValue allowedValue) {
+        this.allowedValue = Objects.requireNonNull(allowedValue);
+    }
+
+    @Override
+    public boolean isValidFor(final JsonValue instance) {
+        return (
+            instance != null && allowedValue.getValueType() == instance.getValueType() && isEqualsToAllowed(instance)
+        );
+    }
+
+    @SuppressWarnings("BigDecimalEquals")
+    private boolean isEqualsToAllowed(final JsonValue instance) {
+        final boolean result;
+        if (InstanceType.NUMBER.isInstance(instance)) {
+            result = ((JsonNumber) instance).bigDecimalValue()
+                .stripTrailingZeros()
+                .equals(((JsonNumber) allowedValue).bigDecimalValue().stripTrailingZeros());
+        } else {
+            result = Objects.equals(allowedValue, instance);
+        }
+        return result;
+    }
+
+    @Override
+    public boolean hasName(final String name) {
+        return Objects.equals(NAME, name);
+    }
+
+    @Override
+    public <T extends Media<T>> T printOn(final T media) {
+        return new JsonObjectPrintable(Json.createObjectBuilder().add(NAME, allowedValue).build()).printOn(media);
+    }
+}

core/src/main/java/io/github/sebastiantoepfer/jsonschema/core/vocab/validation/ValidationVocabulary.java

@@ -24,6 +24,7 @@
 package io.github.sebastiantoepfer.jsonschema.core.vocab.validation;
 
 import io.github.sebastiantoepfer.jsonschema.Vocabulary;
+import io.github.sebastiantoepfer.jsonschema.core.keyword.type.AnyKeywordType;
 import io.github.sebastiantoepfer.jsonschema.core.keyword.type.ArrayKeywordType;
 import io.github.sebastiantoepfer.jsonschema.core.keyword.type.BooleanKeywordType;
 import io.github.sebastiantoepfer.jsonschema.core.keyword.type.IntegerKeywordType;
@@ -44,6 +45,7 @@ public ValidationVocabulary(final JsonProvider jsonContext) {
         this.vocab = new DefaultVocabulary(
             URI.create("https://json-schema.org/draft/2020-12/vocab/validation"),
             new TypeKeywordType(),
+            new AnyKeywordType(ConstKeyword.NAME, ConstKeyword::new),
             new ArrayKeywordType(EnumKeyword.NAME, EnumKeyword::new),
             new StringKeywordType(jsonContext, PatternKeyword.NAME, PatternKeyword::new),
             new IntegerKeywordType(jsonContext, MinLengthKeyword.NAME, MinLengthKeyword::new),

core/src/test/java/io/github/sebastiantoepfer/jsonschema/core/vocab/validation/ConstKeywordTest.java

@@ -0,0 +1,146 @@
+/*
+ * The MIT License
+ *
+ * Copyright 2024 sebastian.
+ *
+ * Permission is hereby granted, free of charge, to any person obtaining a copy
+ * of this software and associated documentation files (the "Software"), to deal
+ * in the Software without restriction, including without limitation the rights
+ * to use, copy, modify, merge, publish, distribute, sublicense, and/or sell
+ * copies of the Software, and to permit persons to whom the Software is
+ * furnished to do so, subject to the following conditions:
+ *
+ * The above copyright notice and this permission notice shall be included in
+ * all copies or substantial portions of the Software.
+ *
+ * THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
+ * IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
+ * FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
+ * AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
+ * LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
+ * OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN
+ * THE SOFTWARE.
+ */
+package io.github.sebastiantoepfer.jsonschema.core.vocab.validation;
+
+import static org.hamcrest.MatcherAssert.assertThat;
+import static org.hamcrest.Matchers.containsInAnyOrder;
+import static org.hamcrest.Matchers.hasEntry;
+import static org.hamcrest.Matchers.is;
+
+import io.github.sebastiantoepfer.ddd.media.core.HashMapMedia;
+import io.github.sebastiantoepfer.jsonschema.core.DefaultJsonSchemaFactory;
+import io.github.sebastiantoepfer.jsonschema.core.keyword.type.AnyKeywordType;
+import io.github.sebastiantoepfer.jsonschema.keyword.Keyword;
+import jakarta.json.Json;
+import jakarta.json.JsonObject;
+import jakarta.json.JsonValue;
+import org.hamcrest.Matcher;
+import org.junit.jupiter.api.Test;
+
+class ConstKeywordTest {
+
+    @Test
+    void should_know_his_name() {
+        final Keyword enumKeyword = createKeywordFrom(
+            Json.createObjectBuilder().add("const", JsonValue.EMPTY_JSON_ARRAY).build()
+        );
+
+        assertThat(enumKeyword.hasName("const"), is(true));
+        assertThat(enumKeyword.hasName("test"), is(false));
+    }
+
+    @Test
+    void should_be_valid_for_same_string_value() {
+        assertThat(
+            createKeywordFrom(Json.createObjectBuilder().add("const", Json.createValue("hello")).build())
+                .asAssertion()
+                .isValidFor(Json.createValue("hello")),
+            is(true)
+        );
+    }
+
+    @Test
+    void should_be_invalid_for_different_string_value() {
+        assertThat(
+            createKeywordFrom(Json.createObjectBuilder().add("const", Json.createValue("hello")).build())
+                .asAssertion()
+                .isValidFor(Json.createValue("world")),
+            is(false)
+        );
+    }
+
+    @Test
+    void should_be_valid_for_same_number_value() {
+        assertThat(
+            createKeywordFrom(Json.createObjectBuilder().add("const", Json.createValue(3.14159)).build())
+                .asAssertion()
+                .isValidFor(Json.createValue(3.14159)),
+            is(true)
+        );
+    }
+
+    @Test
+    void should_be_invalid_for_value_with_different_type() {
+        assertThat(
+            createKeywordFrom(Json.createObjectBuilder().add("const", Json.createValue(3.14159)).build())
+                .asAssertion()
+                .isValidFor(Json.createValue("pi")),
+            is(false)
+        );
+    }
+
+    @Test
+    void should_be_valid_for_exact_object_structure() {
+        assertThat(
+            createKeywordFrom(
+                Json.createObjectBuilder()
+                    .add("const", Json.createObjectBuilder().add("name", "John Doe").add("age", 31))
+                    .build()
+            )
+                .asAssertion()
+                .isValidFor(Json.createObjectBuilder().add("name", "John Doe").add("age", 31).build()),
+            is(true)
+        );
+    }
+
+    @Test
+    void should_be_invalid_for_not_exact_object_structure() {
+        assertThat(
+            createKeywordFrom(
+                Json.createObjectBuilder()
+                    .add("const", Json.createObjectBuilder().add("name", "John Doe").add("age", 31))
+                    .build()
+            )
+                .asAssertion()
+                .isValidFor(Json.createObjectBuilder().add("name", "Robert").add("age", 31).build()),
+            is(false)
+        );
+    }
+
+    @Test
+    void should_be_valid_for_decimal_without_scale_if_number_is_valid() {
+        assertThat(
+            createKeywordFrom(Json.createObjectBuilder().add("const", 1).build())
+                .asAssertion()
+                .isValidFor(Json.createValue(1.0)),
+            is(true)
+        );
+    }
+
+    @Test
+    void should_be_printable() {
+        assertThat(
+            createKeywordFrom(
+                Json.createObjectBuilder().add("const", Json.createArrayBuilder().add("TEST").add("VALID")).build()
+            ).printOn(new HashMapMedia()),
+            (Matcher) hasEntry(is("const"), containsInAnyOrder("TEST", "VALID"))
+        );
+    }
+
+    private static Keyword createKeywordFrom(final JsonObject json) {
+        return new AnyKeywordType("const", ConstKeyword::new).createKeyword(
+            new DefaultJsonSchemaFactory().create(json)
+        );
+    }
+}