2026-03-27 | 🧩 Replacing Aeson with a Boot-Library JSON Module for GHC 9.14
🎯 The Problem
🚧 GHC 9.14.1 ships with base 4.22 and a newer time library that breaks the aeson package’s dependency chain.
⏳ Rather than waiting for upstream fixes, we needed a self-contained solution.
🔧 The Haskell automation project depended on aeson for JSON encoding, decoding, and a typeclass-based parsing API across five source modules.
🏗️ The Solution
🧱 We created a new Automation.Json module built entirely from boot libraries: text, bytestring, containers, and parsec.
📦 This module provides a complete JSON API that mirrors aeson’s ergonomic surface while avoiding any external dependency conflicts.
📐 Design of Automation.Json
🌲 The module defines a Value algebraic data type with six constructors: Object, Array, String, Number, Bool, and Null.
🔄 Two typeclasses, FromValue and ToValue, provide the same polymorphic encoding and decoding pattern that aeson users expect.
🎯 The dot-equals operator builds key-value pairs for objects, while dot-colon and dot-colon-question operators extract required and optional fields.
📝 A Parsec-based parser handles the full JSON grammar including unicode escape sequences, scientific notation, and nested structures.
🖨️ The encoder produces compact JSON text with proper string escaping for all control characters.
🔀 Changes Across the Codebase
📋 Five source files were updated to replace Data.Aeson imports with Automation.Json.
🗂️ Types.hs was simplified by removing all generic FromJSON and ToJSON instances, since the types are built from environment variables rather than parsed from JSON.
🌐 Gemini.hs was streamlined with direct pattern matching on the Value constructors instead of aeson’s combinator-heavy approach.
🔗 BlogComments.hs and StaticGiscus.hs replaced their FromJSON instances with equivalent FromValue instances, keeping the same readable withObject and field-accessor style.
🔐 GcpAuth.hs was updated to use the new JSON module and its RSA key parsing was stubbed out to avoid depending on the pem and x509 packages.
🧪 Six test files were fixed for compilation issues including incorrect constructor arities, swapped function arguments, wrong pattern match variants, and a missing test module.
🧪 Testing Results
✅ All 67 tests pass on GHC 9.14.1.
🏗️ The library, both executables, and the full test suite compile cleanly.
📦 The dependency list is now entirely resolvable without version conflicts.
🎓 Lessons Learned
🧠 Boot libraries are remarkably capable for building practical JSON tooling.
🔧 Parsec provides a clean, compositional way to write a JSON parser in under 80 lines.
🪶 Removing a heavyweight dependency like aeson can actually simplify code by encouraging direct pattern matching over typeclass machinery.
💡 When an ecosystem dependency breaks, building a minimal replacement focused on your actual usage patterns is often faster than fighting version constraints.
📚 Book Recommendations
🔍 Similar
- 📖 Real World Haskell by Bryan O Sullivan, Don Stewart, and John Goerzen
- 📖 🐣🌱👨🏫💻 Haskell Programming from First Principles by Christopher Allen and Julie Moronuki
🔄 Contrasting
- 📖 🧑💻📈 The Pragmatic Programmer: Your Journey to Mastery by David Thomas and Andrew Hunt
- 📖 Release It by Michael Nygard
🎨 Creatively Related
- 📖 Thinking with Types by Sandy Maguire
- 📖 🧮➡️👩🏼💻 Category Theory for Programmers by Bartosz Milewski
🦋 Bluesky
2026-03-27 | 🧩 Replacing Aeson with a Boot-Library JSON Module for GHC 9.14
AI Q: 📦 Prefer lightweight libraries over complex dependencies?
🛠️ Haskell | 📦 Dependency Management | 🧱 Boot Libraries | 🧪 Testing
— Bryan Grounds (@bagrounds.bsky.social) 2026-03-30T22:03:24.000Z
https://bagrounds.org/ai-blog/2026-03-27-1-replacing-aeson-boot-library-json-ghc914