Demo project showing how to use Yaegi to load and execute Go code at runtime.

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The HTTP handler is defined in rule/rule.go and hot-reloaded by Yaegi.

• Go 1.22+

Start the demo server:

make run

Send a request:

curl localhost:8080 -i

Example response (truncated):

HTTP/1.1 200 OK
Cache-Control: no-cache
Content-Type: text/plain; charset=utf-8
Via: useless-helper
Date: Thu, 23 Nov 2023 12:24:31 GMT
Content-Length: 241

Hello!
Your Content-Type is
Your User-Agent is curl/8.1.2
Your Host is localhost:8080
Your RemoteAddr is 127.0.0.1:61784
Your RequestURI is /
Your Method is GET
Your Proto is HTTP/1.1
Your URL is /
Code above is wrote by GitHub Copilot.

:)

Edit rule/rule.go and save; the server response updates without restart.

• --rule (default: ./rule/rule.go): rule file path

• make generate: regenerate Yaegi symbols
• make build: build binary into output/yaegi_demo

To call host-compiled functions from the script:

1. Add a function to a host package (for example internal/helper).
2. Register that package in internal/symbol/symbol.go via a //go:generate yaegi extract <module path> line.
3. Run make generate to refresh Yaegi symbols.
4. Import and call it from rule/rule.go.

Under the hood, yaegi extract generates files like internal/symbol/github_com-dcjanus-yaegi_demo-internal-helper.go. These files define the external symbols the engine can load, and only registered symbols can be used in rule/rule.go.

Example (already in this repo):

// rule/rule.go
import "github.com/dcjanus/yaegi_demo/internal/helper"

// ...
helper.UselessHelper(w, helper.UselessHeader)

.
├── cmd
│   └── main.go         # Program entry
├── internal
│   ├── engine          # Yaegi execution & reload
│   ├── helper          # Demo helpers
│   └── symbol          # Interpreter symbols
├── rule
│   └── rule.go          # Hot-reloaded handler
├── Makefile             # Dev commands
├── README.md            # Project overview
├── README.zh_CN.md      # Chinese README
├── go.mod               # Module definition
└── go.sum               # Dependency checksums