Add validation for length trait values

smithy-model/src/main/java/software/amazon/smithy/model/validation/validators/LengthTraitValidator.java

@@ -0,0 +1,58 @@
+/*
+ * Copyright 2019 Amazon.com, Inc. or its affiliates. All Rights Reserved.
+ *
+ * Licensed under the Apache License, Version 2.0 (the "License").
+ * You may not use this file except in compliance with the License.
+ * A copy of the License is located at
+ *
+ *  http://aws.amazon.com/apache2.0
+ *
+ * or in the "license" file accompanying this file. This file 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 software.amazon.smithy.model.validation.validators;
+
+import java.util.ArrayList;
+import java.util.List;
+import java.util.stream.Collectors;
+import software.amazon.smithy.model.Model;
+import software.amazon.smithy.model.shapes.Shape;
+import software.amazon.smithy.model.traits.LengthTrait;
+import software.amazon.smithy.model.traits.Trait;
+import software.amazon.smithy.model.validation.AbstractValidator;
+import software.amazon.smithy.model.validation.ValidationEvent;
+import software.amazon.smithy.utils.Pair;
+
+public class LengthTraitValidator extends AbstractValidator {
+    @Override
+    public List<ValidationEvent> validate(Model model) {
+        return model.shapes()
+                .flatMap(shape -> Trait.flatMapStream(shape, LengthTrait.class))
+                .flatMap(pair -> validateLengthTrait(model, pair.getLeft(), pair.getRight()).stream())
+                .collect(Collectors.toList());
+    }
+
+    private List<ValidationEvent> validateLengthTrait(Model model, Shape shape, LengthTrait trait) {
+        List<ValidationEvent> events = new ArrayList<>();
+        trait.getMin()
+                .filter(min -> min < 0)
+                .map(min -> error(shape, trait, "A length trait is applied with a negative `min` value."))
+                .ifPresent(events::add);
+
+        trait.getMax()
+                .filter(max -> max < 0)
+                .map(max -> error(shape, trait, "A length trait is applied with a negative `max` value."))
+                .ifPresent(events::add);
+
+        trait.getMin()
+                .flatMap(min -> trait.getMax().map(max -> Pair.of(min, max)))
+                .filter(pair -> pair.getLeft() > pair.getRight())
+                .map(pair -> error(shape, trait, "A length trait is applied with a `min` value greater than "
+                        + "its `max` value."))
+                .map(events::add);
+        return events;
+    }
+}

smithy-model/src/main/resources/META-INF/services/software.amazon.smithy.model.validation.Validator

@@ -15,6 +15,7 @@ software.amazon.smithy.model.validation.validators.HttpPrefixHeadersTraitValidat
 software.amazon.smithy.model.validation.validators.HttpQueryTraitValidator
 software.amazon.smithy.model.validation.validators.HttpResponseCodeSemanticsValidator
 software.amazon.smithy.model.validation.validators.HttpUriConflictValidator
+software.amazon.smithy.model.validation.validators.LengthTraitValidator
 software.amazon.smithy.model.validation.validators.PaginatedTraitValidator
 software.amazon.smithy.model.validation.validators.PrivateAccessValidator
 software.amazon.smithy.model.validation.validators.RangeTraitValidator

smithy-model/src/test/resources/software/amazon/smithy/model/errorfiles/validators/length-trait.errors

@@ -0,0 +1,3 @@
+[ERROR] ns.foo#Invalid1: A length trait is applied with a negative `max` value. | LengthTrait
+[ERROR] ns.foo#Invalid2: A length trait is applied with a negative `min` value. | LengthTrait
+[ERROR] ns.foo#Invalid3: A length trait is applied with a `min` value greater than its `max` value. | LengthTrait

smithy-model/src/test/resources/software/amazon/smithy/model/errorfiles/validators/length-trait.json

@@ -0,0 +1,73 @@
+{
+    "smithy": "0.4.0",
+    "ns.foo": {
+        "shapes": {
+            "Valid1": {
+                "type": "list",
+                "member": {
+                    "target": "smithy.api#String"
+                },
+                "smithy.api#length": {
+                    "min": 0
+                }
+            },
+            "Valid2": {
+                "type": "list",
+                "member": {
+                    "target": "smithy.api#String"
+                },
+                "smithy.api#length": {
+                    "max": 1
+                }
+            },
+            "Valid3": {
+                "type": "list",
+                "member": {
+                    "target": "smithy.api#String"
+                },
+                "smithy.api#length": {
+                    "min": 0,
+                    "max": 1
+                }
+            },
+            "Valid4": {
+                "type": "list",
+                "member": {
+                    "target": "smithy.api#String"
+                },
+                "smithy.api#length": {
+                    "min": 4,
+                    "max": 4
+                }
+            },
+            "Invalid1": {
+                "type": "list",
+                "member": {
+                    "target": "smithy.api#String"
+                },
+                "smithy.api#length": {
+                    "max": -1
+                }
+            },
+            "Invalid2": {
+                "type": "list",
+                "member": {
+                    "target": "smithy.api#String"
+                },
+                "smithy.api#length": {
+                    "min": -1
+                }
+            },
+            "Invalid3": {
+                "type": "list",
+                "member": {
+                    "target": "smithy.api#String"
+                },
+                "smithy.api#length": {
+                    "min": 5,
+                    "max": 4
+                }
+            }
+        }
+    }
+}