How do I set up authentication headers with elm-graphql?

Use the --header flag when running the CLI tool to include headers like Bearer tokens during code generation, and ensure your HTTP requests in Elm pass these headers, as mentioned in the setup instructions.

elm-graphql vs other Elm GraphQL libraries like graphql-to-elm?

elm-graphql is the only library that provides full type safety by generating code from the entire schema, whereas others may rely on runtime checks or manual decoders, offering better correctness guarantees but with code generation overhead.

How to handle real-time updates with elm-graphql subscriptions?

Generate subscription code using the CLI, then set up WebSocket connections via Elm ports with JavaScript, as detailed in the subscription example and demo—this requires external wiring beyond the generated Elm code.

Can I use elm-graphql with a local GraphQL schema file?

Yes, point the CLI tool to a local schema file or introspection endpoint; it supports various inputs, but you'll need to ensure the schema is accessible during code generation, similar to the remote endpoint examples.

How to update generated code when the GraphQL schema changes?

Re-run the elm-graphql CLI tool with the same arguments to regenerate the Elm modules; this is necessary to keep type safety, but it can break existing code if schema changes are incompatible.

Does elm-graphql support custom scalar types?

Yes, through Scalar Codecs, allowing you to define how custom GraphQL scalars are encoded and decoded in Elm, providing flexibility for complex data types as highlighted in the tutorial resources.

elm-graphql — Type-Safe Elm GraphQL Codegen

What is elm-graphql?

dillonkearns/elm-graphql is a tool that autogenerates type-safe Elm code from a GraphQL schema. It allows developers to write GraphQL queries in Elm that are guaranteed to be valid at compile time and automatically handles JSON decoding for API responses. This solves the problem of manual decoder writing and runtime errors when interacting with GraphQL APIs.

Target Audience

Elm developers building frontend applications that consume GraphQL APIs, particularly those who value type safety and want to eliminate runtime errors in their data fetching logic.

Value Proposition

Developers choose elm-graphql because it is the only Elm GraphQL library that provides full type safety across the entire schema, generates decoders automatically, and integrates GraphQL concepts naturally into Elm's functional paradigm. Its compile-time guarantees reduce bugs and improve developer confidence.

Overview

Autogenerate type-safe GraphQL queries in Elm.

Use Cases

Best For

Building Elm frontends with type-safe GraphQL API integration
Eliminating manual JSON decoder writing for GraphQL responses
Ensuring GraphQL query validity at compile time in Elm projects
Creating real-time applications using GraphQL Subscriptions in Elm
Teams adopting GraphQL who want strong static typing in their Elm codebase
Converting GraphQL schemas into reusable, composable Elm modules

Not Ideal For

Projects that require dynamic GraphQL query construction at runtime based on user input
Teams unwilling to integrate a Node.js CLI tool and code generation step into their build process
Applications needing GraphQL Subscriptions with zero manual JavaScript or WebSocket configuration

Pros & Cons

Pros

Compile-Time Query Validation

Generates Elm code that ensures all GraphQL queries are valid according to the schema at compile time, eliminating runtime errors from malformed queries as emphasized in the README.

Automatic JSON Decoders

Seamlessly creates decoders for API responses without manual coding, reducing boilerplate and potential bugs, as demonstrated in the example code snippets.

Native Elm Constructs

Replaces GraphQL variables and fragments with standard Elm functions and constants, providing a simpler, more idiomatic developer experience within Elm's functional paradigm.

Subscriptions Code Generation

Generates ready-to-use Elm code for GraphQL Subscriptions, facilitating real-time updates when combined with WebSocket ports, as shown in the live demo and examples.

Cons

Manual Subscription Wiring

Requires custom JavaScript code and Elm ports to handle WebSocket connections for subscriptions, as the library does not manage low-level transport details, adding complexity.

Code Generation Overhead

Adds a build step with the CLI tool that must be run whenever the GraphQL schema changes, increasing setup and maintenance effort compared to runtime GraphQL clients.

Static Query Building

Queries are constructed statically in Elm code, making it difficult to dynamically generate or modify queries at runtime, which can limit flexibility for interactive applications.

elm-graphql

What is elm-graphql?

Overview

Use Cases

Best For

Not Ideal For

Pros & Cons

Pros

Cons

Frequently Asked Questions

Related Projects

Found a gem we're missing?

elm-graphql

What is elm-graphql?

Overview

Use Cases

Best For

Not Ideal For

Pros & Cons

Pros

Cons

Frequently Asked Questions

Related Projects

Found a gem we're missing?