☯️ Yaml::Merge
if ci_badges.map(&:color).detect { it != "green"} ☝️ let me know on Discord or RubyForum, as I may have missed the notification.
if ci_badges.map(&:color).all? { it == "green"} 👇️ send money so I can do more of this. FLOSS maintenance is now my full-time job.
👣 How will this project approach the September 2025 hostile takeover of RubyGems? 🚑️
I've summarized my thoughts in this blog post.
🌻 Synopsis 
Yaml::Merge is the canonical YAML family package. It is the YAML substrate for
StructuredMerge Ruby: it registers the tree-sitter YAML path and should own the
shared YAML merge behavior used by all YAML backends, including psych-merge.
YAML parsing and backend selection enter through tree_haver; source-preserving
partial document insertion, replacement, and removal should enter through
ast-crispr; merge orchestration should use ast-merge.
Direct parser calls in YAML merge behavior are a smell. Tree-sitter YAML details belong behind the TreeHaver backend path, and Psych details belong behind the Psych TreeHaver backend. YAML-family code should operate on normalized owners, ranges, comments, and edit plans rather than native Ruby Hash/Array round-trips.
Key Features
- YAML mapping-root validation.
- Backend feature profiles for the shared language-pack parser.
- Path-based owner matching for mapping entries.
- Shared YAML-family merge semantics for provider gems such as
psych-merge. - Destination-wins array policy.
- Hash result API for fixture runners and higher-level tools.
💡 Info you can shake a stick at
| Tokens to Remember |   |
|---|---|
| Works with MRI Ruby 4 |  |
| Support & Community |      |
| Source |     |
| Documentation |      |
| Compliance |      |
| Style |     |
| Maintainer 🎖️ |      |
... 💖 |
    🧊 🐙 🛖 🧪 |
Compatibility
Compatible with MRI Ruby 4.0.0+, and concordant releases of JRuby, and TruffleRuby.
CI workflows and Appraisals are generated for MRI Ruby 4.0.0+.
This test floor is configured by ruby.test_minimum in .kettle-jem.yml and
may be higher than the gem's runtime compatibility floor when legacy Rubies are
not practical for the current toolchain.
The amazing test matrix is powered by the kettle-dev stack.
How kettle-dev manages complexity in tests
| Gem | Source | Role | Total downloads |
|---|---|---|---|
| appraisal2 | GitHub | multi-dependency Appraisal matrix generation |  |
| appraisal2-rubocop | GitHub | RuboCop Appraisal generator integration |  |
| kettle-dev | GitHub | development, release, and CI workflow tooling |  |
| kettle-jem | GitHub | Appraisals & CI workflow templates |  |
| kettle-soup-cover | GitHub | SimpleCov coverage policy and reporting |  |
| kettle-test | GitHub | standard test runner and coverage harness |  |
| rubocop-lts | GitHub | Ruby-version-aware linting |  |
| turbo_tests2 | GitHub | parallel test execution |  |
✨ Installation
Install the gem and add to the application's Gemfile by executing:
bundle add yaml-merge
If bundler is not being used to manage dependencies, install the gem by executing:
gem install yaml-merge
⚙️ Configuration
Yaml::Merge exposes module-level functions rather than a mutable global configuration object.
profile = Yaml::Merge.yaml_backend_feature_profile
context = Yaml::Merge.yaml_plan_context
Pass backend: when calling parse_yaml, merge_yaml, or the profile helpers if you need to assert a specific backend. Unsupported backends return structured diagnostics instead of silently falling back.
🔧 Basic Usage
require "yaml/merge"
result = Yaml::Merge.merge_yaml(
File.read("template.yml"),
File.read("config.yml"),
"yaml",
)
abort result.fetch(:diagnostics).inspect unless result.fetch(:ok)
File.write("config.yml", result.fetch(:output))
Most module-level merge methods return a Hash with :ok, :diagnostics, :output, and :policies. Check :ok before writing the result; diagnostics are structured for CI output and fixture conformance reports.
🔐 Security
See SECURITY.md.
🤝 Contributing
If you need some ideas of where to help, you could work on adding more code coverage, or if it is already 💯 (see below) check issues or PRs, or use the gem and think about how it could be better.
We so if you make changes, remember to update it.
See CONTRIBUTING.md for more detailed instructions.
Code Coverage
Coverage service badges
📌 Versioning
This library follows for its public API where practical.
For most applications, prefer the Pessimistic Version Constraint with two digits of precision.
For example:
spec.add_dependency("yaml-merge", "~> 7.0")
📌 Is "Platform Support" part of the public API? More details inside.
Dropping support for a platform can be a breaking change for affected users. If a release changes supported platforms, it should be called out clearly in the changelog and versioned with that impact in mind.
To get a better understanding of how SemVer is intended to work over a project's lifetime, read this article from the creator of SemVer:
See CHANGELOG.md for a list of releases.
📄 License
The gem is available under the following licenses: AGPL-3.0-only, PolyForm-Small-Business-1.0.0. See LICENSE.md for details.
If none of the available licenses suit your use case, please contact us to discuss a custom commercial license.