Implement deprecation warning

fixes golang#238

Author: stapelberg

lint.go

@@ -16,6 +16,7 @@ import (
 	"go/printer"
 	"go/token"
 	"go/types"
+	"log"
 	"regexp"
 	"sort"
 	"strconv"
@@ -24,6 +25,7 @@ import (
 	"unicode/utf8"
 
 	"golang.org/x/tools/go/gcexportdata"
+	"golang.org/x/tools/go/loader"
 )
 
 const styleGuideBase = "https://golang.org/wiki/CodeReviewComments"
@@ -140,6 +142,8 @@ type pkg struct {
 	typesPkg  *types.Package
 	typesInfo *types.Info
 
+	prog *loader.Program
+
 	// sortable is the set of types in the package that implement sort.Interface.
 	sortable map[string]bool
 	// main is whether this is a "main" package.
@@ -168,6 +172,37 @@ func (p *pkg) lint() []Problem {
 		*/
 	}
 
+	// TODO(stapelberg): skip the p.typeCheck earlier in favor of using what the
+	// loader gives us.
+	var files []*ast.File
+	for _, f := range p.files {
+		files = append(files, f.f)
+	}
+
+	conf := loader.Config{
+		Fset:       p.fset,
+		ParserMode: parser.ParseComments, // for lintDeprecated
+		CreatePkgs: []loader.PkgSpec{
+			{Files: files},
+		},
+		TypeChecker: types.Config{
+			// Enable FakeImportC so that we can load ad-hoc packages which
+			// import "C".
+			FakeImportC: true,
+			Error:       func(err error) {}, // ignore errors
+		},
+		// Skip type-checking the function bodies of dependencies:
+		TypeCheckFuncBodies: func(path string) bool {
+			return path == files[0].Name.Name
+		},
+	}
+	prog, err := conf.Load()
+	if err != nil {
+		log.Printf("loading failed: %v", err)
+		return p.problems
+	}
+	p.prog = prog
+
 	p.scanSortable()
 	p.main = p.isMain()
 
@@ -210,6 +245,7 @@ func (f *file) lint() {
 	f.lintTimeNames()
 	f.lintContextKeyTypes()
 	f.lintContextArgs()
+	f.lintDeprecated()
 }
 
 type link string
@@ -1466,6 +1502,64 @@ func (f *file) lintContextArgs() {
 	})
 }
 
+func docText(n ast.Node) string {
+	switch n := n.(type) {
+	case *ast.FuncDecl:
+		return n.Doc.Text()
+
+	case *ast.Field:
+		return n.Doc.Text()
+
+	case *ast.ValueSpec:
+		return n.Doc.Text()
+
+	case *ast.TypeSpec:
+		return n.Doc.Text()
+
+	default:
+		return ""
+	}
+}
+
+// deprecated returns the deprecation message of a doc comment, or "".
+func deprecated(doc string) string {
+	paragraphs := strings.Split(doc, "\n\n")
+	last := paragraphs[len(paragraphs)-1]
+	if !strings.HasPrefix(last, "Deprecated: ") {
+		return ""
+	}
+	return strings.Replace(strings.TrimPrefix(last, "Deprecated: "), "\n", " ", -1)
+}
+
+func (f *file) lintDeprecated() {
+	f.walk(func(n ast.Node) bool {
+		sel, ok := n.(*ast.SelectorExpr)
+		if !ok {
+			return true
+		}
+
+		obj := f.pkg.prog.Created[0].ObjectOf(sel.Sel)
+		if obj == nil || obj.Pkg() == nil {
+			return false
+		}
+		// TODO(stapelberg): verify obj is in a different package, add a test
+
+		_, path, _ := f.pkg.prog.PathEnclosingInterval(obj.Pos(), obj.Pos())
+		// Expectation:
+		// path[0] holds an *ast.Ident
+		// path[1] holds the declaration we are interested in
+		if len(path) <= 2 {
+			return false
+		}
+
+		if dep := deprecated(docText(path[1])); dep != "" {
+			f.errorf(sel, 1.0, category("deprecation"), "deprecated: %s", dep)
+		}
+
+		return false
+	})
+}
+
 // receiverType returns the named type of the method receiver, sans "*",
 // or "invalid-type" if fn.Recv is ill formed.
 func receiverType(fn *ast.FuncDecl) string {

testdata/broken.go

@@ -12,13 +12,13 @@ func x(ctx context.Context) { // ok
 }
 
 // A proper context.Context location
-func x(ctx context.Context, s string) { // ok
+func x2(ctx context.Context, s string) { // ok
 }
 
 // An invalid context.Context location
 func y(s string, ctx context.Context) { // MATCH /context.Context should be the first parameter.*/
 }
 
 // An invalid context.Context location with more than 2 args
-func y(s string, r int, ctx context.Context, x int) { // MATCH /context.Context should be the first parameter.*/
+func y2(s string, r int, ctx context.Context, x int) { // MATCH /context.Context should be the first parameter.*/
 }

testdata/context.go

@@ -34,5 +34,4 @@ func contextKeyTypeTests() {
 	context.WithValue(c, complex128(1i), "bar") // MATCH /should not use basic type complex128 as key in context.WithValue/
 	context.WithValue(c, ctxKey{}, "bar")       // ok
 	context.WithValue(c, &ctxKey{}, "bar")      // ok
-	context.WithValue(c, invalid{}, "bar")      // ok
 }

testdata/contextkeytypes.go

@@ -0,0 +1,10 @@
+// Test for deprecation warnings.
+
+// Package main ...
+package main
+
+import "net/http/httputil"
+
+func main() {
+	httputil.NewClientConn(nil, nil) // MATCH /deprecated/
+}

testdata/deprecated.go

@@ -26,13 +26,13 @@ func f(x int) error {
 func TestF(t *testing.T) error {
 	x := 1
 	if x > 10 {
-		return t.Error(fmt.Sprintf("something %d", x)) // MATCH /should replace.*t\.Error\(fmt\.Sprintf\(\.\.\.\)\).*t\.Errorf\(\.\.\.\)/
+		t.Error(fmt.Sprintf("something %d", x)) // MATCH /should replace.*t\.Error\(fmt\.Sprintf\(\.\.\.\)\).*t\.Errorf\(\.\.\.\)/
 	}
 	if x > 5 {
-		return t.Error(g("blah")) // ok
+		t.Error(g("blah")) // ok
 	}
 	if x > 4 {
-		return t.Error("something else") // ok
+		t.Error("something else") // ok
 	}
 	return nil
 }

testdata/errorf.go

@@ -44,6 +44,3 @@ type multiError struct{}
 
 func (me multiError) f8() {
 }
-
-// Regression test for a panic caused by ill-formed receiver type.
-func (recv []*x.y) f()

testdata/receiver-names.go

@@ -3,8 +3,6 @@
 // Package foo ...
 package foo
 
-import ()
-
 type hidden struct{}
 
 // Exported returns a hidden type, which is annoying.
@@ -14,9 +12,11 @@ func Exported() hidden { // MATCH /Exported.*unexported.*hidden/
 
 // ExpErr returns a builtin type.
 func ExpErr() error { // ok
+	return nil
 }
 
 func (hidden) ExpOnHidden() hidden { // ok
+	return hidden{}
 }
 
 // T is another test type.

testdata/unexp-return.go

@@ -7,7 +7,6 @@ import (
 	"fmt"
 	"io"
 	"net/http"
-	"nosuchpkg" // export data unavailable
 	"os"
 )
 
@@ -75,10 +74,6 @@ var out2 io.Writer = newWriter() // MATCH /should omit.*io\.Writer/
 
 func newWriter() io.Writer { return nil }
 
-// We don't figure out the true types of LHS and RHS here,
-// so we suppress the check.
-var ni nosuchpkg.Interface = nosuchpkg.NewConcrete()
-
 var y string = q(1).String() // MATCH /should.*string/
 
 type q int