$ show sangria-graphql/sangria
Sangria is a comprehensive GraphQL execution library for Scala that implements the full GraphQL specification. It provides a type-safe domain-specific language for defining GraphQL schemas (ObjectType, InterfaceType, UnionType, EnumType, InputObjectType, ScalarType, etc.), a parser for GraphQL query and Schema Definition Language (SDL), a validation engine with over 20 built-in validation rules, and an asynchronous execution engine supporting deferred resolution, middleware, query reducers, and subscriptions. The library is modular with separate artifacts for AST representation, parsing, core execution, and macro-based schema derivation, and integrates with cats-effect, fs2, Monix, and various JSON marshalling libraries (spray-json, circe, play-json, etc.). The architecture is based on immutable case classes, visitor patterns for validation and AST traversal, typeclass-based marshalling, and a composable Action ADT for field resolution that supports values, futures, deferred values, and context updates. The codebase demonstrates strong engineering practices with extensive cross-compilation across Scala 2.12, 2.13, and 3.3, binary compatibility management via MiMa, automated CI/CD, and thorough test coverage including yaml-based scenario tests for validation and execution.
The LLM identified 4 files worth highlighting for reuse:
A minimal, self-contained caching trait with three implementations (ConcurrentHashMapCache, TrieMapCache, and an abstract cache). It provides basic get/put and computeIfAbsent operations. This is easily extractable and reusable in any Scala project needing a simple concurrent cache with monotonic time metrics.
A pluggable framework for pre-execution query analysis. Defines a sealed trait QueryReducer with concrete reducers for measuring complexity, depth, collecting tags, and blocking introspection. Reducers accumulate state from collected fields and can reject queries based on thresholds. The pattern is decoupled from the execution internals and can be reused in other GraphQL or query analysis contexts.
A mechanism for generating optimized projections of query fields for use in data fetching. Uses a sealed ProjectorHierarchy trait and ProjectedName to represent the type-safe, nested structure of selected fields. This enables efficient batch data loading (e.g., only fetch requested columns from a database). The pattern is self-contained and could be applied to any query optimization problem that needs to communicate selected fields to data resolvers.
A base trait for GraphQL validation rules that follows a visitor pattern with onEnter/onLeave callbacks on AST nodes. Provides a validation context with error collection, severity levels, and built-in helpers for type checking and rule composition. This pattern can be extracted and reused in any validation framework that needs to traverse an AST with extensible rules.