gweaver

A simple source code weaver for Go programs

Method

• Put the weaves in their own directory (default is ext) with a fully qualified package path
• Ensure the weaver executable is in the PATH
• Run go build cmd/weaver/weaver.go ; ./weaver -weaveDir ext -writeDir /tmp/

Weaving

1. Each woven package gets a unique directory under weaveDir
2. All weaves for a package go into the same directory
3. Each weave go file corresponds directly to the original package go file

• Pick-up the weave definition files from the ext directory
• Read the weave's AST
• Using the package/module from the weave's path get the target package's AST
• Modify the target AST per the weave
• Copy the entire modified module to a local 'fork'
• Write the modified AST to the fork
• add a replace original/module => forked/module to go.mod
  • If we have to support non vgo Go's we can 'fork' in the GOPATH

To Do

• Comprehensive test suite
• Documentation
• Refactor the package init code, make the steps less implicit

Annotations

• // +weaver delete
• // +weaver insert
• // +weaver update
• // +weaver updateAndCallOriginal

References

• https://golang.org/pkg/go/ast/
• https://github.com/fatih/astrewrite/blob/master/astrewrite.go
• https://godoc.org/golang.org/x/tools/go/ast/astutil
• https://zupzup.org/ast-manipulation-go/
• https://zupzup.org/go-ast-traversal/
• https://godoc.org/golang.org/x/tools/go/ast/inspector
• https://arslan.io/2017/09/14/the-ultimate-guide-to-writing-a-go-tool/
• https://github.com/golang/tools/blob/master/cmd/stringer/stringer.go