How to write a programming language and shell in Go with 92% test coverage and instant CI/CD-Qi Xiao

Go proved to be an excellent language for implementing Elvish shell, providing garbage collection, goroutines, and standard library features that simplified development

The interpreter follows a three-stage process: parsing source code into syntax tree, converting to operation tree, and execution - each stage using divide-and-conquer on tree structures

Testing was made extremely easy through recording terminal transcripts in text files, eliminating separate test writing steps and contributing to 92% test coverage

Elvish improves on traditional shells by supporting proper data structures (lists, maps), functional programming with lambdas, and concurrent pipeline execution using goroutines

The shell provides modern features like syntax highlighting, command history with filtering, file navigation, and programmable prompts using lambdas instead of special sequences

CI/CD was implemented using GitHub webhooks and Go HTTP listeners that trigger Elvish scripts to build binaries

The terminal app uses a widget-based architecture with event handling and rendering methods, similar to GUI programming patterns

Test coverage was achieved by making testing an integral part of development rather than a separate step - manual testing is converted directly into test cases

Fuzzing was used effectively to test the parser for crashes and performance issues, as well as ensuring markdown formatting preserved semantics

The project leverages Go’s standard library extensively, with many Elvish features mapping directly to Go equivalents (big numbers, string manipulation, etc.)