1 files changed, 176 insertions, 0 deletions
diff --git a/vendor/github.com/charithe/durationcheck/durationcheck.go b/vendor/github.com/charithe/durationcheck/durationcheck.go
new file mode 100644
index 000000000..6eccd9c2a
--- /dev/null
+++ b/vendor/github.com/charithe/durationcheck/durationcheck.go
@@ -0,0 +1,176 @@
+package durationcheck
+
+import (
+	"bytes"
+	"fmt"
+	"go/ast"
+	"go/format"
+	"go/token"
+	"go/types"
+	"log"
+	"os"
+
+	"golang.org/x/tools/go/analysis"
+	"golang.org/x/tools/go/analysis/passes/inspect"
+	"golang.org/x/tools/go/ast/inspector"
+)
+
+var Analyzer = &analysis.Analyzer{
+	Name:     "durationcheck",
+	Doc:      "check for two durations multiplied together",
+	Run:      run,
+	Requires: []*analysis.Analyzer{inspect.Analyzer},
+}
+
+func run(pass *analysis.Pass) (interface{}, error) {
+	// if the package does not import time, it can be skipped from analysis
+	if !hasImport(pass.Pkg, "time") {
+		return nil, nil
+	}
+
+	inspect := pass.ResultOf[inspect.Analyzer].(*inspector.Inspector)
+
+	nodeTypes := []ast.Node{
+		(*ast.BinaryExpr)(nil),
+	}
+
+	inspect.Preorder(nodeTypes, check(pass))
+
+	return nil, nil
+}
+
+func hasImport(pkg *types.Package, importPath string) bool {
+	for _, imp := range pkg.Imports() {
+		if imp.Path() == importPath {
+			return true
+		}
+	}
+
+	return false
+}
+
+// check contains the logic for checking that time.Duration is used correctly in the code being analysed
+func check(pass *analysis.Pass) func(ast.Node) {
+	return func(node ast.Node) {
+		expr := node.(*ast.BinaryExpr)
+		// we are only interested in multiplication
+		if expr.Op != token.MUL {
+			return
+		}
+
+		// get the types of the two operands
+		x, xOK := pass.TypesInfo.Types[expr.X]
+		y, yOK := pass.TypesInfo.Types[expr.Y]
+
+		if !xOK || !yOK {
+			return
+		}
+
+		if isDuration(x.Type) && isDuration(y.Type) {
+			// check that both sides are acceptable expressions
+			if isUnacceptableExpr(pass, expr.X) && isUnacceptableExpr(pass, expr.Y) {
+				pass.Reportf(expr.Pos(), "Multiplication of durations: `%s`", formatNode(expr))
+			}
+		}
+	}
+}
+
+func isDuration(x types.Type) bool {
+	return x.String() == "time.Duration"
+}
+
+// isUnacceptableExpr returns true if the argument is not an acceptable time.Duration expression
+func isUnacceptableExpr(pass *analysis.Pass, expr ast.Expr) bool {
+	switch e := expr.(type) {
+	case *ast.BasicLit:
+		return false
+	case *ast.Ident:
+		return !isAcceptableNestedExpr(pass, e)
+	case *ast.CallExpr:
+		return !isAcceptableCast(pass, e)
+	case *ast.BinaryExpr:
+		return !isAcceptableNestedExpr(pass, e)
+	case *ast.UnaryExpr:
+		return !isAcceptableNestedExpr(pass, e)
+	case *ast.SelectorExpr:
+		return !isAcceptableNestedExpr(pass, e)
+	}
+
+	return true
+}
+
+// isAcceptableCast returns true if the argument is an acceptable expression cast to time.Duration
+func isAcceptableCast(pass *analysis.Pass, e *ast.CallExpr) bool {
+	// check that there's a single argument
+	if len(e.Args) != 1 {
+		return false
+	}
+
+	// check that the argument is acceptable
+	if !isAcceptableNestedExpr(pass, e.Args[0]) {
+		return false
+	}
+
+	// check for time.Duration cast
+	selector, ok := e.Fun.(*ast.SelectorExpr)
+	if !ok {
+		return false
+	}
+
+	return isDurationCast(selector)
+}
+
+func isDurationCast(selector *ast.SelectorExpr) bool {
+	pkg, ok := selector.X.(*ast.Ident)
+	if !ok {
+		return false
+	}
+
+	if pkg.Name != "time" {
+		return false
+	}
+
+	return selector.Sel.Name == "Duration"
+}
+
+func isAcceptableNestedExpr(pass *analysis.Pass, n ast.Expr) bool {
+	switch e := n.(type) {
+	case *ast.BasicLit:
+		return true
+	case *ast.BinaryExpr:
+		return isAcceptableNestedExpr(pass, e.X) && isAcceptableNestedExpr(pass, e.Y)
+	case *ast.UnaryExpr:
+		return isAcceptableNestedExpr(pass, e.X)
+	case *ast.Ident:
+		return isAcceptableIdent(pass, e)
+	case *ast.CallExpr:
+		t := pass.TypesInfo.TypeOf(e)
+		return !isDuration(t)
+	case *ast.SelectorExpr:
+		t := pass.TypesInfo.TypeOf(e)
+		return !isDuration(t)
+	}
+
+	return false
+}
+
+func isAcceptableIdent(pass *analysis.Pass, ident *ast.Ident) bool {
+	obj := pass.TypesInfo.ObjectOf(ident)
+	return !isDuration(obj.Type())
+}
+
+func formatNode(node ast.Node) string {
+	buf := new(bytes.Buffer)
+	if err := format.Node(buf, token.NewFileSet(), node); err != nil {
+		log.Printf("Error formatting expression: %v", err)
+		return ""
+	}
+
+	return buf.String()
+}
+
+func printAST(msg string, node ast.Node) {
+	fmt.Printf(">>> %s:\n%s\n\n\n", msg, formatNode(node))
+	ast.Fprint(os.Stdout, nil, node, nil)
+	fmt.Println("--------------")
+}