Fix false-positives for github.com/pkg/errors functions

[r2k1]

Add support for errors.WithMessagef( and errors.WithStack(

Wrapcheck complains about the next code:

package store

import (
	"database/sql"
	stderrors "errors"

	"github.com/pkg/errors"
)

var ErrNoRowsAffected = stderrors.New("no rows affected")
var ErrMultipleRowsAffected = stderrors.New("multiple rows affected")

// EnsureOneRowAffected ensures that a single row was affected by db.ExecWithResult.
func EnsureOneRowAffected(res sql.Result, err error) error {
	if err != nil {
		return err
	}

	rows, err := res.RowsAffected()
	if err != nil {
		return errors.Wrap(err, "could not fetch information about affected rows")
	}

	if rows == 0 {
		return errors.WithStack(ErrNoRowsAffected)
	}

	if rows > 1 {
		return errors.WithStack(ErrMultipleRowsAffected)
	}

	return nil
}

error returned from external package is unwrapped: sig: func github.com/pkg/errors.WithStack(err error) error (wrapcheck)
                return errors.WithStack(ErrNoRowsAffected)

[r2k1]

How do you test it?

I got the next error when trying to run it:

=== RUN   TestAnalyzer/ignore_pkg_errors
main.go:6:2: cannot find package "github.com/pkg/errors" in any of:
	/usr/local/go/src/github.com/pkg/errors (from $GOROOT)
	/Users/r2k1/projects/wrapcheck/wrapcheck/testdata/ignore_pkg_errors/src/github.com/pkg/errors (from $GOPATH)
/Users/r2k1/projects/wrapcheck/wrapcheck/testdata/ignore_pkg_errors/main.go:6:2: could not import github.com/pkg/errors (invalid package name: "")
    analysistest.go:274: error analyzing wrapcheck@_/Users/r2k1/projects/wrapcheck/wrapcheck/testdata/ignore_pkg_errors: analysis skipped due to errors in package
    --- FAIL: TestAnalyzer/ignore_pkg_errors (1.16s)

[tomarrell]

Hey man! Long time no chat, how're things?

Yeah the test issue was a limitation of analysistest not yet supporting go mod unfortunately, golang/go#37054. Have now manually vendored and resolved it on master, then rebased this PR.

PR looks good, thanks for the contribution! 😃