Introduction

This library handles go-coverage files. It provides semantic coverage profile merging function. Check merge/merge.go for more details.

Example:

go test -run TestMergeProfile -v ./merge

Old Coverage:

New Coverage:

Merged Coverage:

Algorithm

The algorithm implementation is at merge/merge.go.

First, traverse the old and new AST tree to get each basic block's cleaned code. Simply put, cleaned code is code that gets compiled into assembly, excluding any space and comments.

Then, use myers diff to find unchanged blocks, see ComputeBlockMapping.In this step we map all blocks in new AST to their unchanged counterpart in old AST.

Finally, use the new-to-old mapping to merge counters, for unchanged blocks, counters are added together.

The algorithm effectively provides incrimental testing coverage across muiltpe changes(e.g. multiple git commits).

Diff

go generate ./...

Required go version: 1.16

When build with go1.14:

$ with-go1.14 go build ./...
# github.com/dop251/goja/parser
../../gopath/pkg/mod/github.com/dop251/goja@v0.0.0-20221229151140-b95230a9dbad/parser/parser.go:150:9: undefined: os.ReadFile
../../gopath/pkg/mod/github.com/dop251/goja@v0.0.0-20221229151140-b95230a9dbad/parser/statement.go:901:19: undefined: os.ReadFile
note: module requires Go 1.16