v1.4.0 (#141)

README.md

@@ -6,7 +6,7 @@ GraphQL stitching composes a single schema from multiple underlying GraphQL reso
 
 **Supports:**
 - Merged object and abstract types.
-- Multiple keys per merged type.
+- Multiple and composite keys per merged type.
 - Shared objects, fields, enums, and inputs across locations.
 - Combining local and remote schemas.
 - File uploads via [multipart form spec](https://github.com/jaydenseric/graphql-multipart-request-spec).
@@ -94,7 +94,7 @@ To facilitate this merging of types, stitching must know how to cross-reference
 Types merge through resolver queries identified by a `@stitch` directive:
 
 ```graphql
-directive @stitch(key: String!) repeatable on FIELD_DEFINITION
+directive @stitch(key: String!, arguments: String) repeatable on FIELD_DEFINITION
 ```
 
 This directive (or [static configuration](#sdl-based-schemas)) is applied to root queries where a merged type may be accessed in each location, and a `key` argument specifies a field needed from other locations to be used as a query argument.
@@ -151,7 +151,7 @@ type Query {
 ```
 
 * The `@stitch` directive is applied to a root query where the merged type may be accessed. The merged type identity is inferred from the field return.
-* The `key: "id"` parameter indicates that an `{ id }` must be selected from prior locations so it may be submitted as an argument to this query. The query argument used to send the key is inferred when possible ([more on arguments](#multiple-query-arguments) later).
+* The `key: "id"` parameter indicates that an `{ id }` must be selected from prior locations so it may be submitted as an argument to this query. The query argument used to send the key is inferred when possible ([more on arguments](#argument-shapes) later).
 
 Each location that provides a unique variant of a type must provide at least one resolver query for the type. The exception to this requirement are [outbound-only types](./docs/mechanics.md#outbound-only-merged-types) and/or [foreign key types](./docs/mechanics.md##modeling-foreign-keys-for-stitching) that contain no exclusive data:
 
@@ -198,7 +198,7 @@ type Query {
 To customize which types an abstract query provides and their respective keys, you may extend the `@stitch` directive with a `typeName` constraint. This can be repeated to select multiple types.
 
 ```graphql
-directive @stitch(key: String!, typeName: String) repeatable on FIELD_DEFINITION
+directive @stitch(key: String!, arguments: String, typeName: String) repeatable on FIELD_DEFINITION
 
 type Product { sku: ID! }
 type Order { id: ID! }
@@ -212,19 +212,69 @@ type Query {
 }
 ```
 
-#### Multiple query arguments
+#### Argument shapes
 
-Stitching infers which argument to use for queries with a single argument, or when the key name matches its intended argument. For queries that accept multiple arguments with unmatched names, the key should provide an argument alias specified as `"<arg>:<key>"`.
+Stitching infers which argument to use for queries with a single argument, or when the key name matches its intended argument. For custom mappings, the `arguments` option may specify a template of GraphQL arguments that insert key selections:
 
 ```graphql
 type Product {
   id: ID!
 }
 type Query {
-  product(byId: ID, bySku: ID): Product @stitch(key: "byId:id")
+  product(byId: ID, bySku: ID): Product
+    @stitch(key: "id", arguments: "byId: $.id")
 }
 ```
 
+Key insertions are prefixed by `$` and specify a dot-notation path to any selections made by the resolver `key`, or `__typename`. This syntax allows sending multiple arguments that intermix stitching keys with complex input shapes and other static values:
+
+```graphql
+type Product {
+  id: ID!
+}
+union Entity = Product
+input EntityKey {
+  id: ID!
+  type: String!
+}
+
+type Query {
+  entities(keys: [EntityKey!]!, source: String="database"): [Entity]!
+    @stitch(key: "id", arguments: "keys: { id: $.id, type: $.__typename }, source: 'cache'")
+}
+```
+
+See [resolver arguments](./docs/resolver.md#arguments) for full documentation on shaping input.
+
+#### Composite type keys
+
+Resolver keys may make composite selections for multiple key fields and/or nested scopes, for example:
+
+```graphql
+interface FieldOwner {
+  id: ID!
+  type: String!
+}
+type CustomField {
+  owner: FieldOwner!
+  key: String!
+  value: String
+}
+input CustomFieldLookup {
+  ownerId: ID!
+  ownerType: String!
+  key: String!
+}
+type Query {
+  customFields(lookups: [CustomFieldLookup!]!): [CustomField]! @stitch(
+    key: "owner { id type } key",
+    arguments: "lookups: { ownerId: $.owner.id, ownerType: $.owner.type, key: $.key }"
+  )
+}
+```
+
+Note that composite key selections may _not_ be distributed across locations. The complete selection criteria must be available in each location that provides the key.
+
 #### Multiple type keys
 
 A type may exist in multiple locations across the graph using different keys, for example:

docs/resolver.md

@@ -0,0 +1,101 @@
+## GraphQL::Stitching::Resolver
+
+A `Resolver` contains all information about a root query used by stitching to fetch location-specific variants of a merged type. Specifically, resolvers manage parsed keys and argument structures.
+
+### Arguments
+
+Resolvers configure arguments through a template string of [GraphQL argument literal syntax](https://spec.graphql.org/October2021/#sec-Language.Arguments). This allows sending multiple arguments that intermix stitching keys with complex object shapes and other static values.
+
+#### Key insertions
+
+Key values fetched from previous locations may be inserted into arguments. Key insertions are prefixed by `$` and specify a dot-notation path to any selections made by the resolver `key`, or `__typename`.
+
+```graphql
+type Query {
+  entity(id: ID!, type: String!): [Entity]!
+    @stitch(key: "owner { id }", arguments: "id: $.owner.id, type: $.__typename")
+}
+```
+
+Key insertions are _not_ quoted to differentiate them from other literal values.
+
+#### Lists
+
+List arguments may specify input just like non-list arguments, and [GraphQL list input coercion](https://spec.graphql.org/October2021/#sec-List.Input-Coercion) will assume the shape represents a list item:
+
+```graphql
+type Query {
+  product(ids: [ID!]!, source: DataSource!): [Product]!
+    @stitch(key: "id", arguments: "ids: $.id, source: CACHE")
+}
+```
+
+List resolvers (that return list types) may _only_ insert keys into repeatable list arguments, while non-list arguments may only contain static values. Nested list inputs are neither common nor practical, so are not supported.
+
+#### Built-in scalars
+
+Built-in scalars are written as normal literal values. For convenience, string literals may be enclosed in single quotes rather than escaped double-quotes:
+
+```graphql
+type Query {
+  product(id: ID!, source: String!): Product
+    @stitch(key: "id", arguments: "id: $.id, source: 'cache'")
+
+  variant(id: ID!, limit: Int!): Variant
+    @stitch(key: "id", arguments: "id: $.id, limit: 100")
+}
+```
+
+All scalar usage must be legal to the resolver field's arguments schema.
+
+#### Enums
+
+Enum literals may be provided anywhere in the input structure. They are _not_ quoted:
+
+```graphql
+enum DataSource {
+  CACHE
+}
+type Query {
+  product(id: ID!, source: DataSource!): [Product]!
+    @stitch(key: "id", arguments: "id: $.id, source: CACHE")
+}
+```
+
+All enum usage must be legal to the resolver field's arguments schema.
+
+#### Input Objects
+
+Input objects may be provided anywhere in the input, even as nested structures. The stitching resolver will build the specified object shape:
+
+```graphql
+input ComplexKey {
+  id: ID
+  nested: ComplexKey
+}
+type Query {
+  product(key: ComplexKey!): [Product]!
+    @stitch(key: "id", arguments: "key: { nested: { id: $.id } }")
+}
+```
+
+Input object shapes must conform to their respective schema definitions based on their placement within resolver arguments.
+
+#### Custom scalars
+
+Custom scalar keys allow any input shape to be submitted, from primitive scalars to complex object structures. These values will be sent and recieved as untyped JSON input:
+
+```graphql
+type Product {
+  id: ID!
+}
+union Entity = Product
+scalar Key
+
+type Query {
+  entities(representations: [Key!]!): [Entity]!
+    @stitch(key: "id", arguments: "representations: { id: $.id, __typename: $.__typename }")
+}
+```
+
+Custom scalar arguments have no structured schema definition to validate against. This makes them flexible but quite lax, for better or worse.

lib/graphql/stitching.rb

@@ -8,6 +8,8 @@ module Stitching
     EMPTY_ARRAY = [].freeze
 
     class StitchingError < StandardError; end
+    class CompositionError < StitchingError; end
+    class ValidationError < CompositionError; end
 
     class << self
       def stitch_directive
@@ -28,7 +30,6 @@ def stitching_directive_names
 require_relative "stitching/client"
 require_relative "stitching/composer"
 require_relative "stitching/executor"
-require_relative "stitching/export_selection"
 require_relative "stitching/http_executable"
 require_relative "stitching/plan"
 require_relative "stitching/planner_step"

lib/graphql/stitching/client.rb

@@ -70,7 +70,11 @@ def on_error(&block)
       def load_plan(request)
         if @on_cache_read && plan_json = @on_cache_read.call(request)
           plan = GraphQL::Stitching::Plan.from_json(JSON.parse(plan_json))
-          return request.plan(plan)
+
+          # only use plans referencing current resolver versions
+          if plan.ops.all? { |op| !op.resolver || @supergraph.resolvers_by_version[op.resolver] }
+            return request.plan(plan)
+          end
         end
 
         plan = request.plan