Implement support for github.com/jackc/pgx

[hallabro]

These changes add support for github.com/jackc/pgx (including pgxpool).

Two of the biggest changes with this implementation:

1. The pgx functions return interface types. Because of this we need to check for instr.Call.Method calls as well instr.Call.Value.
2. For the same reason we need to check for Named types in addition to Pointer types.

There was an issue with the tests in pkg/analyzer that would not allow the tests to run with external packages. From the documentation for analysistest.Run:

// If the directory contains a go.mod file, Run treats it as the root of the
// Go module in which to work. Otherwise, Run treats it as the root of a
// GOPATH-style tree, with package contained in the src subdirectory.

The solution was to add a go.mod and vendor in the pkg/analyzer/testdata directory. This leads to some packages being vendored twice unfortunately but I see no easy solution around this.

This is the first time I write some linter/static code analyzer tool so any feedback is appreciated.

Thanks.

Closes #23.

[ryanrolds]

Thank you. I will take a look at this by the end of the weekend.

[ryanrolds]

Thank you. This is overall great work, and look forward to merging it. 😸

I have one question about a variable rename and would like to see some of the new code DRYed out a bit. Happy to chat about strategies to eliminate the repeated code. This is my first linter too, I'm learning with each change as well.

[ryanrolds]

Another example. There are a couple more areas. Don't worry about the Value and Method paths.

[hallabro]

Can you please elaborate on the Value and Method paths? They don't seem to be part of the code that you highlighted in your comment.

[hallabro]

Thanks for the feedback Ryan! I'll have a look at your comments today.

[hallabro]

I have pushed some changes around the duplicate code. Thanks for pointing it out! All this type casting is making it a little bit difficult for me to fully understand what's going on sometimes.

Hopefully I've responded to your other comments as well. Let me know what you think.

I'd happily continue to work on the code until it reaches a mergeable state.

[ryanrolds]

I was thinking something like:

func getTargetTypesValues(b *ssa.BasicBlock, i int, targetTypes []any) []targetValue {
	targetValues := []targetValue{}

	instr := b.Instrs[i]
	call, ok := instr.(*ssa.Call)
	if !ok {
		return targetValues
	}

	signature := call.Call.Signature()
	results := signature.Results()
	for i := 0; i < results.Len(); i++ {
		v := results.At(i)
		varType := v.Type()

		for _, targetType := range targetTypes {
			switch tt := targetType.(type) {
			case *types.Pointer:
				targetValues = checkAndAddTargetValue(varType, tt, call, targetValues)
			case *types.Named:
				targetValues = checkAndAddTargetValue(varType, tt, call, targetValues)
			}
		}
	}

	return targetValues
}

func checkAndAddTargetValue(varType types.Type, tt types.Type, call *ssa.Call, targetValues []targetValue) []targetValue {
	if !types.Identical(varType, tt) {
		return targetValues
	}

	for _, cRef := range *call.Referrers() {
		switch instr := cRef.(type) {
		case *ssa.Call:
			if len(instr.Call.Args) >= 1 && types.Identical(instr.Call.Args[0].Type(), tt) {
				targetValues = append(targetValues, targetValue{
					value: &instr.Call.Args[0],
					instr: call,
				})
			}
		case ssa.Value:
			if types.Identical(instr.Type(), tt) {
				targetValues = append(targetValues, targetValue{
					value: &instr,
					instr: call,
				})
			}
		}
	}

	return targetValues
}

[ryanrolds]

Thank you. :) Great job.