Update error test case

There were several issues with the error test case that have been
addressed in this commit.

- It is possible to specify a whitelist of calls that error handling
  should be ignored for.
- Additional support for ast.ExprStmt for cases where the error is
  implicitly ignored.

There were several other additions to the helpers and call list in order
to support this type of functionality.

Fixes #54

core/call_list.go

@@ -13,7 +13,9 @@
 
 package core
 
-import "go/ast"
+import (
+	"go/ast"
+)
 
 type set map[string]bool
 
@@ -26,14 +28,11 @@ func NewCallList() CallList {
 	return make(CallList)
 }
 
-/// NewCallListFor createse a call list using the package path
-func NewCallListFor(selector string, idents ...string) CallList {
-	c := NewCallList()
-	c[selector] = make(set)
+/// AddAll will add several calls to the call list at once
+func (c CallList) AddAll(selector string, idents ...string) {
 	for _, ident := range idents {
 		c.Add(selector, ident)
 	}
-	return c
 }
 
 /// Add a selector and call to the call list
@@ -61,5 +60,14 @@ func (c CallList) ContainsCallExpr(n ast.Node, ctx *Context) bool {
 	if err != nil {
 		return false
 	}
-	return c.Contains(selector, ident)
+	// Try direct resolution
+	if c.Contains(selector, ident) {
+		return true
+	}
+
+	// Also support explicit path
+	if path, ok := GetImportPath(selector, ctx); ok {
+		return c.Contains(path, ident)
+	}
+	return false
 }

core/call_list_test.go

@@ -21,13 +21,15 @@ func (r *callListRule) Match(n ast.Node, c *Context) (gi *Issue, err error) {
 func TestCallListContainsCallExpr(t *testing.T) {
 	config := map[string]interface{}{"ignoreNosec": false}
 	analyzer := NewAnalyzer(config, nil)
+	calls := NewCallList()
+	calls.AddAll("bytes.Buffer", "Write", "WriteTo")
 	rule := &callListRule{
 		MetaData: MetaData{
 			Severity:   Low,
 			Confidence: Low,
 			What:       "A dummy rule",
 		},
-		callList: NewCallListFor("bytes.Buffer", "Write", "WriteTo"),
+		callList: calls,
 		matched:  0,
 	}
 	analyzer.AddRule(rule, []ast.Node{(*ast.CallExpr)(nil)})

core/helpers.go

@@ -56,25 +56,17 @@ func MatchCall(n ast.Node, r *regexp.Regexp) *ast.CallExpr {
 //
 func MatchCallByPackage(n ast.Node, c *Context, pkg string, names ...string) (*ast.CallExpr, bool) {
 
-	importName, imported := c.Imports.Imported[pkg]
-	if !imported {
+	importedName, found := GetImportedName(pkg, c)
+	if !found {
 		return nil, false
 	}
 
-	if _, initonly := c.Imports.InitOnly[pkg]; initonly {
-		return nil, false
-	}
-
-	if alias, ok := c.Imports.Aliased[pkg]; ok {
-		importName = alias
-	}
-
 	if callExpr, ok := n.(*ast.CallExpr); ok {
 		packageName, callName, err := GetCallInfo(callExpr, c)
 		if err != nil {
 			return nil, false
 		}
-		if packageName == importName {
+		if packageName == importedName {
 			for _, name := range names {
 				if callName == name {
 					return callExpr, true
@@ -185,7 +177,38 @@ func GetCallInfo(n ast.Node, ctx *Context) (string, string, error) {
 					return expr.Name, fn.Sel.Name, nil
 				}
 			}
+		case *ast.Ident:
+			return ctx.Pkg.Name(), fn.Name, nil
 		}
 	}
 	return "", "", fmt.Errorf("unable to determine call info")
 }
+
+// GetImportedName returns the name used for the package within the
+// code. It will resolve aliases and ignores initalization only imports.
+func GetImportedName(path string, ctx *Context) (string, bool) {
+	importName, imported := ctx.Imports.Imported[path]
+	if !imported {
+		return "", false
+	}
+
+	if _, initonly := ctx.Imports.InitOnly[path]; initonly {
+		return "", false
+	}
+
+	if alias, ok := ctx.Imports.Aliased[path]; ok {
+		importName = alias
+	}
+	return importName, true
+}
+
+// GetImportPath resolves the full import path of an identifer based on
+// the imports in the current context.
+func GetImportPath(name string, ctx *Context) (string, bool) {
+	for path, _ := range ctx.Imports.Imported {
+		if imported, ok := GetImportedName(path, ctx); ok && imported == name {
+			return path, true
+		}
+	}
+	return "", false
+}

rules/errors.go

@@ -15,47 +15,82 @@
 package rules
 
 import (
+	gas "github.com/GoASTScanner/gas/core"
 	"go/ast"
 	"go/types"
-	"reflect"
-
-	gas "github.com/GoASTScanner/gas/core"
 )
 
 type NoErrorCheck struct {
 	gas.MetaData
+	whitelist gas.CallList
 }
 
-func (r *NoErrorCheck) Match(n ast.Node, c *gas.Context) (gi *gas.Issue, err error) {
-	if node, ok := n.(*ast.AssignStmt); ok {
-		sel := reflect.TypeOf(&ast.CallExpr{})
-		if call, ok := gas.SimpleSelect(node.Rhs[0], sel).(*ast.CallExpr); ok {
-			if t := c.Info.Types[call].Type; t != nil {
-				if typeVal, typeErr := t.(*types.Tuple); typeErr {
-					for i := 0; i < typeVal.Len(); i++ {
-						if typeVal.At(i).Type().String() == "error" { // TODO(tkelsey): is there a better way?
-							if id, ok := node.Lhs[i].(*ast.Ident); ok && id.Name == "_" {
-								return gas.NewIssue(c, n, r.What, r.Severity, r.Confidence), nil
+func returnsError(callExpr *ast.CallExpr, ctx *gas.Context) int {
+	if tv := ctx.Info.TypeOf(callExpr); tv != nil {
+		switch t := tv.(type) {
+		case *types.Tuple:
+			for pos := 0; pos < t.Len(); pos += 1 {
+				variable := t.At(pos)
+				if variable != nil && variable.Type().String() == "error" {
+					return pos
+				}
+			}
+		case *types.Named:
+			if t.String() == "error" {
+				return 0
 			}
 		}
 	}
-				} else if t.String() == "error" { // TODO(tkelsey): is there a better way?
-					if id, ok := node.Lhs[0].(*ast.Ident); ok && id.Name == "_" {
-						return gas.NewIssue(c, n, r.What, r.Severity, r.Confidence), nil
+	return -1
+}
+
+func (r *NoErrorCheck) Match(n ast.Node, ctx *gas.Context) (*gas.Issue, error) {
+	switch stmt := n.(type) {
+	case *ast.AssignStmt:
+		for _, expr := range stmt.Rhs {
+			if callExpr, ok := expr.(*ast.CallExpr); ok && !r.whitelist.ContainsCallExpr(callExpr, ctx) {
+				pos := returnsError(callExpr, ctx)
+				if pos < 0 || pos >= len(stmt.Lhs) {
+					return nil, nil
+				}
+				if id, ok := stmt.Lhs[pos].(*ast.Ident); ok && id.Name == "_" {
+					return gas.NewIssue(ctx, n, r.What, r.Severity, r.Confidence), nil
 				}
 			}
 		}
+	case *ast.ExprStmt:
+		if callExpr, ok := stmt.X.(*ast.CallExpr); ok && !r.whitelist.ContainsCallExpr(callExpr, ctx) {
+			pos := returnsError(callExpr, ctx)
+			if pos >= 0 {
+				return gas.NewIssue(ctx, n, r.What, r.Severity, r.Confidence), nil
+			}
 		}
 	}
 	return nil, nil
 }
 
 func NewNoErrorCheck(conf map[string]interface{}) (gas.Rule, []ast.Node) {
+
+	// TODO(gm) Come up with sensible defaults here. Or flip it to use a
+	// black list instead.
+	whitelist := gas.NewCallList()
+	whitelist.AddAll("bytes.Buffer", "Write", "WriteByte", "WriteRune", "WriteString")
+	whitelist.AddAll("fmt", "Print", "Printf", "Println")
+	whitelist.Add("io.PipeWriter", "CloseWithError")
+
+	if configured, ok := conf["G104"]; ok {
+		if whitelisted, ok := configured.(map[string][]string); ok {
+			for key, val := range whitelisted {
+				whitelist.AddAll(key, val...)
+			}
+		}
+	}
 	return &NoErrorCheck{
 		MetaData: gas.MetaData{
 			Severity:   gas.Low,
 			Confidence: gas.High,
 			What:       "Errors unhandled.",
 		},
-	}, []ast.Node{(*ast.AssignStmt)(nil)}
+		whitelist: whitelist,
+	}, []ast.Node{(*ast.AssignStmt)(nil), (*ast.ExprStmt)(nil)}
 }

rules/errors_test.go

@@ -55,15 +55,26 @@ func TestErrorsSingle(t *testing.T) {
 			"fmt"
 		)
 
-    func test() (err error) {
-      return nil
+		func a() error {
+			return fmt.Errorf("This is an error")
+		}
+
+		func b() {
+			fmt.Println("b")
+		}
+
+		func c() string {
+			return fmt.Sprintf("This isn't anything")
 		}
 
 		func main() {
-      _ := test()
+			_ = a()
+			a()
+			b()
+			_ = c()
+			c()
 		}`, analyzer)
-
-	checkTestResults(t, issues, 1, "Errors unhandled")
+	checkTestResults(t, issues, 2, "Errors unhandled")
 }
 
 func TestErrorsGood(t *testing.T) {
@@ -88,3 +99,42 @@ func TestErrorsGood(t *testing.T) {
 
 	checkTestResults(t, issues, 0, "")
 }
+
+func TestErrorsWhitelisted(t *testing.T) {
+	config := map[string]interface{}{
+		"ignoreNosec": false,
+		"G104": map[string][]string{
+			"compress/zlib": []string{"NewReader"},
+			"io":            []string{"Copy"},
+		},
+	}
+	analyzer := gas.NewAnalyzer(config, nil)
+	analyzer.AddRule(NewNoErrorCheck(config))
+	source := `package main
+		import (
+			"io"
+			"os"
+			"fmt"
+			"bytes"
+			"compress/zlib"
+		)
+
+		func a() error {
+			return fmt.Errorf("This is an error ok")
+		}
+
+		func main() {
+			// Expect at least one failure
+			_ = a()
+
+			var b bytes.Buffer
+			// Default whitelist
+			nbytes, _ := b.Write([]byte("Hello "))
+
+			// Whitelisted via configuration
+			r, _ := zlib.NewReader(&b)
+			io.Copy(os.Stdout, r)
+		}`
+	issues := gasTestRunner(source, analyzer)
+	checkTestResults(t, issues, 1, "Errors unhandled")
+}