CUE vs YAML: What are the differences?

Introduction

CUE and YAML are both popular languages used for writing configuration files. While they have some similarities, there are also key differences between them.

1. Document Structure: In YAML, documents are structured using indentation and key-value pairs, making it easy to read and write. On the other hand, CUE uses a more declarative approach, where configurations are defined as rules and constraints. This allows for more strict validation and auto-completion of configuration files.

2. Type System: YAML has a loose and flexible type system, allowing for easy modification and update of configuration values. CUE, on the other hand, has a more strict and robust type system, enabling strong typing and validation of configuration values. This ensures that only valid and expected values are accepted.

3. Syntax: YAML uses indentation and colons for key-value pairs, which can be more readable for humans. CUE, on the other hand, uses braces and colons for defining rules and constraints, which can be more suitable for machines and automated validation processes.

4. Overriding and Composition: In YAML, configuration values can be easily overridden and merged together using techniques like anchors and references. CUE provides a similar functionality called "Struct composition", which allows for building complex configurations by combining simpler ones. However, CUE also offers additional features like default values and field constraints.

5. Validation and Error Handling: YAML provides limited support for validation and error handling, relying on external tools to detect errors or enforce constraints. CUE, on the other hand, has built-in support for validating and enforcing constraints through its type system. It can detect errors and inconsistencies in the configuration file during the build process itself.

6. Extensibility: YAML allows for easy extensibility through the use of custom tags and libraries. CUE also supports extensibility through its schema and package system. It allows for defining reusable configurations and importing them into the main configuration file.

In summary, CUE and YAML have different approaches to configuration file formatting, type systems, syntax, validation, and extensibility. CUE provides a more strict and robust way of defining configurations, with built-in validation and type checking. YAML, on the other hand, offers a simpler and more human-readable format, with ease of extensibility and override capabilities.