go-withcontext-checker

What

Checks that the result of a call to *net/http.Request.WithContext() is assigned to a value

Why

According to the docs:

WithContext returns a shallow copy of r with its context changed to ctx.

Returning a shallow copy instead of modifying the context in-place was surprising behavior to me. This tool checks that all calls to *net/http.Request.WithContext() happens as part of an assignment.

How

./go-withcontext-checker -t github.com/bubaflub/go-withcontext-checker/examples
net/http request.WithContext() called without lvalue at /Users/bob/gohome/src/github.com/bubaflub/go-withcontext-checker/examples/simple_test.go:12:2: "WithContext"`

Todo

• Have tests that run as part of go test
• Print the full line where the call is made
• Provide a fixit hint like clang-tidy does
• Accept a list of functions that we should flag to get GCC's warn_unused_result functionality
• Can we find all "pure" functions in stdlib to generate the list above?
• Open and issue to propose patch to extend go vet