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package sttp.apispec.validation
import sttp.apispec._
import scala.annotation.tailrec
import scala.collection.immutable.ListMap
import scala.collection.mutable
/**
* Utility for comparing schemas for compatibility.
* See [[compare]] for more details.
*
* Since this class contains a cache of comparison results,
* it is meant to be reused between multiple schema comparisons.
*
* @param writerSchemaResolver can resolve named schemas which may be referred to by the writer schema
* @param readerSchemaResolver can resolve named schemas which may be referred to by the reader schema
*/
class SchemaComparator(
writerSchemaResolver: SchemaResolver,
readerSchemaResolver: SchemaResolver
) {
def this(
writerNamedSchemas: Map[String, Schema],
readerNamedSchemas: Map[String, Schema]
) = this(SchemaResolver(writerNamedSchemas), SchemaResolver(readerNamedSchemas))
private val issuesCache = new mutable.HashMap[(Schema, Schema), List[SchemaCompatibilityIssue]]
private val identicalityCache = new mutable.HashMap[(Schema, Schema), Boolean]
/**
* Computes a value for a given key, using a cache. Computation of the value may recursively depend on the same key.
* In such cases, the recursion is short-circuited and the value is assumed to be equal to `recursiveValue`.
*/
private def computeCached[K, V](cache: mutable.Map[K, V], key: K, recursiveValue: V)(compute: => V): V =
cache.get(key) match {
case Some(value) => value
case None =>
cache.put(key, recursiveValue)
val result = try compute finally cache.remove(key)
cache.put(key, result)
result
}
/**
* Compares two schemas for compatibility. More precisely, checks if data that is valid according to [[writerSchema]]
* is also valid according to [[readerSchema]]. If not, a list of compatibility issues is returned.
*
* Determining compatibility (or incompatibility) of arbitrary schemas with certainty is non-trivial, or outright
* impossible in general. For this reason, this method works in a "best effort" manner, assuming that the schemas
* match one of the typical schema patterns generated by libraries like `tapir`. In more complex situations,
* the comparator simply falls back to comparing schemas by plain equality, or returns a [[GeneralSchemaMismatch]],
* which indicates comparator's inability to definitely determine compatibility or incompatibility of the schemas.
*
* In practice, the comparator is designed to detect typical changes that may appear in schemas during API evolution,
* e.g. adding new fields, changing types, etc.
*
* Before being compared, all schemas are stripped of keywords which do not affect the comparison, e.g. annotations
* like `title`, `description`, etc.
*
* @param writerSchema schema of the data being written
* @param readerSchema schema of the data being read
* @return a list of incompatibilities between the schemas
*/
def compare(writerSchema: SchemaLike, readerSchema: SchemaLike): List[SchemaCompatibilityIssue] = {
val normalizedWriterSchema = writerSchemaResolver.resolveAndNormalize(writerSchema)
val normalizedReaderSchema = readerSchemaResolver.resolveAndNormalize(readerSchema)
computeCached(issuesCache, (normalizedWriterSchema, normalizedReaderSchema), Nil) {
compareNormalized(normalizedWriterSchema, normalizedReaderSchema)
}
}
private def compareNormalized(writerSchema: Schema, readerSchema: Schema): List[SchemaCompatibilityIssue] =
if (writerSchema == Schema.Nothing || readerSchema == Schema.Empty) {
Nil
} else if (isPrimitiveSchema(writerSchema) && isPrimitiveSchema(readerSchema)) {
checkType(writerSchema, readerSchema).toList ++
checkEnumAndConst(writerSchema, readerSchema).toList ++
checkFormat(writerSchema, readerSchema).toList ++
checkMultipleOf(writerSchema, readerSchema).toList ++
checkNumericBounds(writerSchema, readerSchema).toList ++
checkStringLengthBounds(writerSchema, readerSchema).toList ++
checkPattern(writerSchema, readerSchema).toList
} else if (isProductSchema(writerSchema) && isProductSchema(readerSchema)) {
// Even though the default value for `additionalProperties` is an empty schema that accepts everything,
// we assume a Nothing schema for the writer because it's extremely unlikely in practice that a value for a
// product type would contain an additional property beyond what's listed in `properties`
val writerAdditionalProps = writerSchema.additionalProperties.getOrElse(Schema.Nothing)
val readerAdditionalProps = readerSchema.additionalProperties.getOrElse(Schema.Empty)
val allPropNames = writerSchema.properties.keySet ++ readerSchema.properties.keySet
val propIssues = allPropNames.toList.flatMap { propName =>
val writerPropSchema = writerSchema.properties.getOrElse(propName, writerAdditionalProps)
val readerPropSchema = readerSchema.properties.getOrElse(propName, readerAdditionalProps)
val issues = compare(writerPropSchema, readerPropSchema)
if (issues.nonEmpty) Some(IncompatibleProperty(propName, issues)) else None
}
checkType(writerSchema, readerSchema).toList ++
checkRequiredProperties(writerSchema, readerSchema).toList ++
checkDependentRequired(writerSchema, readerSchema) ++
propIssues
} else if (isDiscriminatedUnionSchema(writerSchema) && isDiscriminatedUnionSchema(readerSchema)) {
val writerMapping = writerSchemaResolver.discriminatorMapping(writerSchema)
val readerMapping = readerSchemaResolver.discriminatorMapping(readerSchema)
val variantIssues: List[SchemaCompatibilityIssue] =
(writerMapping.keySet intersect readerMapping.keySet).toList.flatMap { tag =>
compare(writerMapping(tag), readerMapping(tag)) match {
case Nil => None
case issues => Some(IncompatibleDiscriminatorCase(tag, issues))
}
}
checkType(writerSchema, readerSchema).toList ++
checkDiscriminatorProp(writerSchema, readerSchema).toList ++
checkDiscriminatorValues(writerMapping, readerMapping).toList ++
variantIssues
} else if (isCollectionSchema(writerSchema) && isCollectionSchema(readerSchema)) {
checkType(writerSchema, readerSchema).toList ++
checkArrayLengthBounds(writerSchema, readerSchema).toList ++
checkUniqueItems(writerSchema, readerSchema).toList ++
checkItems(writerSchema, readerSchema).toList
} else if (isTupleSchema(writerSchema) && isTupleSchema(readerSchema)) {
val writerPrefixItems = writerSchema.prefixItems.getOrElse(Nil)
val readerPrefixItems = readerSchema.prefixItems.getOrElse(Nil)
val prefixItemsIssues = writerPrefixItems
.zipAll(readerPrefixItems, Schema.Empty, Schema.Empty)
.zipWithIndex.flatMap {
case ((writerItem, readerItem), idx) =>
compare(writerItem, readerItem) match {
case Nil => None
case issues => Some(IncompatiblePrefixItem(idx, issues))
}
}
checkType(writerSchema, readerSchema).toList ++
checkArrayLengthBounds(writerSchema, readerSchema).toList ++
prefixItemsIssues
} else if (isMapSchema(writerSchema) && isMapSchema(readerSchema)) {
checkType(writerSchema, readerSchema).toList ++
checkAdditionalProperties(writerSchema, readerSchema).toList ++
checkPropertyNames(writerSchema, readerSchema).toList ++
checkMinMaxProperties(writerSchema, readerSchema).toList
} else if (isUnionSchema(writerSchema)) {
val variants = writerSchema.oneOf ++ writerSchema.anyOf
variants.zipWithIndex.flatMap {
case (variant, idx) => compare(variant, readerSchema) match {
case Nil => None
case issues => Some(IncompatibleUnionVariant(idx, issues))
}
}
} else if (isUnionSchema(readerSchema)) {
val variants = readerSchema.oneOf ++ readerSchema.anyOf
@tailrec def alternatives(
variants: List[SchemaLike],
acc: List[List[SchemaCompatibilityIssue]]
): Option[AlternativeIssues] = variants match {
case Nil => Some(AlternativeIssues(acc.reverse))
case variant :: tail => compare(writerSchema, variant) match {
case Nil => None
case issues => alternatives(tail, issues :: acc)
}
}
alternatives(variants, Nil).toList
} else if (readerSchema == Schema.Nothing) {
List(NoValuesAllowed(writerSchema))
} else checkType(writerSchema, readerSchema) match {
case Some(typeMismatch) => List(typeMismatch)
case None if identical(writerSchema, readerSchema) => Nil
case None =>
// At this point we know that schemas are not equal, and we were unable to produce any
// more specific incompatibility, so we just return a generic issue
List(GeneralSchemaMismatch(writerSchema, readerSchema))
}
/**
* Checks if two (already normalized) schemas are identical. Note: we can't simply compare schemas for equality
* with `==` because local references in the schemas may resolve to different schemas, i.e.
* - identical local references in `writerSchema` and `readerSchema` may resolve to different schemas
* - non-identical local references in `writerSchema` and `readerSchema` may resolve to identical schemas
*/
private def identical(writerSchema: Schema, readerSchema: Schema): Boolean =
(writerSchema eq readerSchema) || computeCached(identicalityCache, (writerSchema, readerSchema), true) {
def identicalSubschema(writerSubschema: SchemaLike, readerSubschema: SchemaLike): Boolean =
identical(writerSchemaResolver.resolveAndNormalize(writerSubschema), readerSchemaResolver.resolveAndNormalize(readerSubschema))
def identicalSubschemaMap[K](writerSubschemas: ListMap[K, SchemaLike], readerSubschemas: ListMap[K, SchemaLike]): Boolean =
(writerSubschemas.keySet ++ readerSubschemas.keySet).forall { key =>
writerSubschemas.get(key).toList.corresponds(readerSubschemas.get(key).toList)(identicalSubschema)
}
removeSubschemas(writerSchema) == removeSubschemas(readerSchema) &&
writerSchema.$defs.toList.corresponds(readerSchema.$defs.toList)(identicalSubschemaMap) &&
writerSchema.allOf.corresponds(readerSchema.allOf)(identicalSubschema) &&
writerSchema.anyOf.corresponds(readerSchema.anyOf)(identicalSubschema) &&
writerSchema.oneOf.corresponds(readerSchema.oneOf)(identicalSubschema) &&
writerSchema.not.toList.corresponds(readerSchema.not.toList)(identicalSubschema) &&
writerSchema.`if`.toList.corresponds(readerSchema.`if`.toList)(identicalSubschema) &&
writerSchema.`then`.toList.corresponds(readerSchema.`then`.toList)(identicalSubschema) &&
writerSchema.`else`.toList.corresponds(readerSchema.`else`.toList)(identicalSubschema) &&
identicalSubschemaMap(writerSchema.dependentSchemas, readerSchema.dependentSchemas) &&
writerSchema.items.toList.corresponds(readerSchema.items.toList)(identicalSubschema) &&
writerSchema.prefixItems.toList.corresponds(readerSchema.prefixItems.toList)((w, r) => w.corresponds(r)(identicalSubschema)) &&
writerSchema.contains.toList.corresponds(readerSchema.contains.toList)(identicalSubschema) &&
writerSchema.unevaluatedItems.toList.corresponds(readerSchema.unevaluatedItems.toList)(identicalSubschema) &&
identicalSubschemaMap(writerSchema.properties, readerSchema.properties) &&
identicalSubschemaMap(writerSchema.patternProperties, readerSchema.patternProperties) &&
writerSchema.additionalProperties.toList.corresponds(readerSchema.additionalProperties.toList)(identicalSubschema) &&
writerSchema.propertyNames.toList.corresponds(readerSchema.propertyNames.toList)(identicalSubschema) &&
writerSchema.unevaluatedProperties.toList.corresponds(readerSchema.unevaluatedProperties.toList)(identicalSubschema)
}
private def removeSubschemas(schema: Schema): Schema =
schema.copy(
$defs = None,
allOf = Nil,
anyOf = Nil,
oneOf = Nil,
not = None,
`if` = None,
`then` = None,
`else` = None,
dependentSchemas = ListMap.empty,
items = None,
prefixItems = None,
contains = None,
unevaluatedItems = None,
properties = ListMap.empty,
patternProperties = ListMap.empty,
additionalProperties = None,
propertyNames = None,
unevaluatedProperties = None,
)
/** Checks if schema is for a _primitive_ value, i.e. a string, boolean, number or null */
private def isPrimitiveSchema(s: Schema): Boolean =
s.`type`.exists { types =>
types.nonEmpty && !types.contains(SchemaType.Array) && !types.contains(SchemaType.Object)
} && s == Schema( // check if the schema contains only primitive type assertions
`type` = s.`type`,
`enum` = s.`enum`,
const = s.`const`,
format = s.format,
multipleOf = s.multipleOf,
minimum = s.minimum,
exclusiveMinimum = s.exclusiveMinimum,
maximum = s.maximum,
exclusiveMaximum = s.exclusiveMaximum,
maxLength = s.maxLength,
minLength = s.minLength,
pattern = s.pattern,
)
private def isCollectionSchema(s: Schema): Boolean =
s.`type`.getOrElse(Nil).filter(_ != SchemaType.Null) == List(SchemaType.Array) &&
s.items.isDefined &&
s == Schema(
`type` = s.`type`,
items = s.items,
maxItems = s.maxItems,
minItems = s.minItems,
uniqueItems = s.uniqueItems,
)
private def isTupleSchema(s: Schema): Boolean =
s.`type`.getOrElse(Nil).filter(_ != SchemaType.Null) == List(SchemaType.Array) &&
s.prefixItems.isDefined &&
s == Schema(
`type` = s.`type`,
prefixItems = s.prefixItems,
maxItems = s.maxItems,
minItems = s.minItems,
)
private def isMapSchema(s: Schema): Boolean =
s.`type`.getOrElse(Nil).filter(_ != SchemaType.Null) == List(SchemaType.Object) &&
s.additionalProperties.isDefined &&
s == Schema(
`type` = s.`type`,
propertyNames = s.propertyNames,
additionalProperties = s.additionalProperties,
maxProperties = s.maxProperties,
minProperties = s.minProperties,
)
private def isProductSchema(s: Schema): Boolean =
s.`type`.getOrElse(Nil).filter(_ != SchemaType.Null) == List(SchemaType.Object) &&
s.properties.nonEmpty &&
s == Schema(
`type` = s.`type`,
properties = s.properties,
required = s.required,
dependentRequired = s.dependentRequired,
)
private def isUnionSchema(s: Schema): Boolean =
// exactly one of `oneOf` and `anyOf` should be non-empty
(s.oneOf.nonEmpty != s.anyOf.nonEmpty) && s == Schema(
oneOf = s.oneOf,
anyOf = s.anyOf,
discriminator = s.discriminator,
)
private def isDiscriminatedUnionSchema(s: Schema): Boolean =
s.discriminator.nonEmpty && isUnionSchema(s)
private def getTypes(schema: Schema): Option[List[SchemaType]] = schema match {
case Schema.Empty => Some(SchemaType.Values)
case Schema.Nothing => Some(Nil)
case s => s.`type`
}
/**
* Checks if all writer types are compatible with at least one reader type.
* This check assumes schemas that have at least one `type` defined.
*/
private def checkType(writerSchema: Schema, readerSchema: Schema): Option[TypeMismatch] =
for {
writerTypes <- getTypes(writerSchema)
readerTypes <- getTypes(readerSchema)
incompatibleWriterTypes =
writerTypes.filter(wtpe => !readerTypes.exists(rtpe => typesCompatible(wtpe, rtpe)))
if incompatibleWriterTypes.nonEmpty
} yield TypeMismatch(incompatibleWriterTypes, readerTypes)
private def typesCompatible(writerTpe: SchemaType, readerTpe: SchemaType): Boolean =
(writerTpe, readerTpe) match {
case (SchemaType.Integer, SchemaType.Number) => true
case _ => writerTpe == readerTpe
}
private def checkEnumAndConst(writerSchema: Schema, readerSchema: Schema): Option[EnumMismatch] = {
val writerEnum = writerSchema.const.map(List(_)).orElse(writerSchema.`enum`)
val readerEnum = readerSchema.const.map(List(_)).orElse(readerSchema.`enum`)
(writerEnum, readerEnum) match {
case (None, Some(readerValues)) =>
Some(EnumMismatch(None, readerValues))
case (Some(writerValues), Some(readerValues)) =>
val incompatibleWriterValues =
writerValues.filter(wv => !readerValues.contains(wv))
if (incompatibleWriterValues.isEmpty) None
else Some(EnumMismatch(Some(incompatibleWriterValues), readerValues))
case _ =>
None
}
}
private def checkFormat(writerSchema: Schema, readerSchema: Schema): Option[FormatMismatch] =
(writerSchema.format, readerSchema.format) match {
case (None, Some(readerFormat)) =>
Some(FormatMismatch(None, readerFormat))
case (Some(writerFormat), Some(readerFormat)) if !formatsCompatible(writerFormat, readerFormat) =>
Some(FormatMismatch(Some(writerFormat), readerFormat))
case _ => None
}
private def formatsCompatible(writerFormat: String, readerFormat: String): Boolean =
(writerFormat, readerFormat) match {
case (SchemaFormat.Int32, SchemaFormat.Int64) => true
case (SchemaFormat.Float | SchemaFormat.Int32, SchemaFormat.Double) => true
case _ => writerFormat == readerFormat
}
private def checkMultipleOf(writerSchema: Schema, readerSchema: Schema): Option[MultipleOfMismatch] =
(writerSchema.multipleOf, readerSchema.multipleOf) match {
case (None, Some(readerMultiplier)) =>
Some(MultipleOfMismatch(None, readerMultiplier))
case (Some(writerMultiplier), Some(readerMultiplier)) if !(writerMultiplier / readerMultiplier).isWhole =>
Some(MultipleOfMismatch(Some(writerMultiplier), readerMultiplier))
case _ =>
None
}
private def bounds(schema: Schema): Bounds[BigDecimal] = Bounds(
schema.minimum
.map(Bound.inclusive)
.orElse(schema.exclusiveMinimum.map(Bound.exclusive)),
schema.maximum
.map(Bound.inclusive)
.orElse(schema.exclusiveMaximum.map(Bound.exclusive))
)
private def checkNumericBounds(writerSchema: Schema, readerSchema: Schema): Option[NumericBoundsMismatch] = {
val writerBounds = bounds(writerSchema)
val readerBounds = bounds(readerSchema)
if (readerBounds.contains(writerBounds)) None
else Some(NumericBoundsMismatch(writerBounds, readerBounds))
}
private def stringLengthBounds(schema: Schema): Bounds[Int] = Bounds(
Some(Bound.inclusive(schema.minLength.getOrElse(0))),
schema.maxLength.map(Bound.inclusive)
)
private def checkStringLengthBounds(
writerSchema: Schema,
readerSchema: Schema
): Option[StringLengthBoundsMismatch] = {
val writerBounds = stringLengthBounds(writerSchema)
val readerBounds = stringLengthBounds(readerSchema)
if (readerBounds.contains(writerBounds)) None
else Some(StringLengthBoundsMismatch(writerBounds, readerBounds))
}
private def checkPattern(writerSchema: Schema, readerSchema: Schema): Option[PatternMismatch] =
(writerSchema.pattern, readerSchema.pattern) match {
case (None, Some(readerPattern)) =>
Some(PatternMismatch(None, readerPattern))
case (Some(writerPattern), Some(readerPattern)) if writerPattern != readerPattern =>
Some(PatternMismatch(Some(writerPattern), readerPattern))
case _ =>
None
}
private def checkUniqueItems(writerSchema: Schema, readerSchema: Schema): Option[UniqueItemsRequired.type] =
(writerSchema.uniqueItems, readerSchema.uniqueItems) match {
case (None | Some(false), Some(true)) => Some(UniqueItemsRequired)
case _ => None
}
private def arrayLengthBounds(schema: Schema): Bounds[Int] = Bounds(
Some(Bound.inclusive(schema.minItems.getOrElse(0))),
schema.maxItems.map(Bound.inclusive)
)
private def checkArrayLengthBounds(writerSchema: Schema, readerSchema: Schema): Option[ArrayLengthBoundsMismatch] = {
val writerBounds = arrayLengthBounds(writerSchema)
val readerBounds = arrayLengthBounds(readerSchema)
if (readerBounds.contains(writerBounds)) None
else Some(ArrayLengthBoundsMismatch(writerBounds, readerBounds))
}
private def checkItems(writerSchema: Schema, readerSchema: Schema): Option[IncompatibleItems] = {
val writerItems = writerSchema.items.getOrElse(Schema.Empty)
val readerItems = readerSchema.items.getOrElse(Schema.Empty)
compare(writerItems, readerItems) match {
case Nil => None
case issues => Some(IncompatibleItems(issues))
}
}
private def objectMinMaxProperties(schema: Schema): Bounds[Int] = Bounds(
Some(Bound.inclusive(schema.minProperties.getOrElse(0))),
schema.maxProperties.map(Bound.inclusive)
)
private def checkMinMaxProperties(writerSchema: Schema, readerSchema: Schema): Option[ObjectSizeBoundsMismatch] = {
val writerBounds = objectMinMaxProperties(writerSchema)
val readerBounds = objectMinMaxProperties(readerSchema)
if (readerBounds.contains(writerBounds)) None
else Some(ObjectSizeBoundsMismatch(writerBounds, readerBounds))
}
private def checkRequiredProperties(writerSchema: Schema, readerSchema: Schema): Option[MissingRequiredProperties] = {
val newRequired = readerSchema.required.toSet -- writerSchema.required.toSet
if (newRequired.isEmpty) None
else Some(MissingRequiredProperties(newRequired))
}
private def checkDependentRequired(writerSchema: Schema, readerSchema: Schema): List[MissingDependentRequiredProperties] =
readerSchema.dependentRequired.toList.flatMap { case (property, required) =>
// if the writer schema does not require or define a schema for this property, we assume that it will never
// be passed (even if it's implicitly allowed by patternProperties/additionalProperties)
val writerMentionsProperty =
writerSchema.properties.contains(property) || writerSchema.required.contains(property)
val writerRequired = writerSchema.dependentRequired
.get(property)
.orElse(if (writerMentionsProperty) Some(Nil) else None)
writerRequired.flatMap { wr =>
val moreRequired = required.toSet -- wr.toSet
if (moreRequired.isEmpty) None
else Some(MissingDependentRequiredProperties(property, moreRequired))
}
}
private def checkDiscriminatorProp(
writerSchema: Schema,
readerSchema: Schema
): Option[DiscriminatorPropertyMismatch] = for {
writerDiscProp <- writerSchema.discriminator.map(_.propertyName)
readerDiscProp <- readerSchema.discriminator.map(_.propertyName)
if writerDiscProp != readerDiscProp
} yield DiscriminatorPropertyMismatch(writerDiscProp, readerDiscProp)
private def checkDiscriminatorValues(
writerMapping: ListMap[String, SchemaLike],
readerMapping: ListMap[String, SchemaLike],
): Option[UnsupportedDiscriminatorValues] = {
val unsupportedValues = writerMapping.keySet -- readerMapping.keySet
if (unsupportedValues.nonEmpty)
Some(UnsupportedDiscriminatorValues(unsupportedValues.toList))
else None
}
private def checkPropertyNames(
writerSchema: Schema,
readerSchema: Schema,
): Option[IncompatiblePropertyNames] = {
val writerPropertyNames = writerSchema.propertyNames.getOrElse(Schema(SchemaType.String))
val readerPropertyNames = readerSchema.propertyNames.getOrElse(Schema(SchemaType.String))
compare(writerPropertyNames, readerPropertyNames) match {
case Nil => None
case issues => Some(IncompatiblePropertyNames(issues))
}
}
private def checkAdditionalProperties(
writerSchema: Schema,
readerSchema: Schema,
): Option[IncompatibleAdditionalProperties] = {
val writerProps = writerSchema.additionalProperties.getOrElse(Schema.Empty)
val readerProps = readerSchema.additionalProperties.getOrElse(Schema.Empty)
compare(writerProps, readerProps) match {
case Nil => None
case issues => Some(IncompatibleAdditionalProperties(issues))
}
}
}
