Allow *testing.T as first parameter for context parameter check

Fixes mgechev#422

rule/context-as-argument.go

@@ -46,7 +46,15 @@ func (w lintContextArguments) Visit(n ast.Node) ast.Visitor {
 	// A context.Context should be the first parameter of a function.
 	// Flag any that show up after the first.
 	previousArgIsCtx := isPkgDot(fn.Type.Params.List[0].Type, "context", "Context")
-	for _, arg := range fn.Type.Params.List[1:] {
+	// In case that the first parameter is *testing.T, we don't want
+	// to fail the linter. For example:
+	// 		func testContext(t *testint.T, ctx context.Context)
+	firstArgIsTestingT := isPtrPkgDot(fn.Type.Params.List[0].Type, "testing", "T")
+	remArgs := fn.Type.Params.List[1:]
+	if firstArgIsTestingT && len(fn.Type.Params.List) > 1 {
+		remArgs = fn.Type.Params.List[2:]
+	}
+	for _, arg := range remArgs {
 		argIsCtx := isPkgDot(arg.Type, "context", "Context")
 		if argIsCtx && !previousArgIsCtx {
 			w.onFailure(lint.Failure{

rule/utils.go

@@ -92,11 +92,18 @@ func validType(T types.Type) bool {
 		!strings.Contains(T.String(), "invalid type") // good but not foolproof
 }
 
+// isPkgDot checks if the expression is <pkg>.<name>
 func isPkgDot(expr ast.Expr, pkg, name string) bool {
 	sel, ok := expr.(*ast.SelectorExpr)
 	return ok && isIdent(sel.X, pkg) && isIdent(sel.Sel, name)
 }
 
+// isPtrPkgDot checks if the expression is *<pkg>.<name>.
+func isPtrPkgDot(expr ast.Expr, pkg, name string) bool {
+	star, ok := expr.(*ast.StarExpr)
+	return ok && isPkgDot(star.X, pkg, name)
+}
+
 func srcLine(src []byte, p token.Position) string {
 	// Run to end of line in both directions if not at line start/end.
 	lo, hi := p.Offset, p.Offset+1

testdata/golint/context-as-argument.go

@@ -5,6 +5,7 @@ package foo
 
 import (
 	"context"
+	"testing"
 )
 
 // A proper context.Context location
@@ -15,6 +16,10 @@ func x(ctx context.Context) { // ok
 func x(ctx context.Context, s string) { // ok
 }
 
+// A test helper function with context object allowes context to be not the first argument.
+func x(t *testing.T, ctx context.Context) { // ok
+}
+
 // An invalid context.Context location
 func y(s string, ctx context.Context) { // MATCH /context.Context should be the first parameter of a function/
 }