Support for archive mode

README.md

@@ -28,7 +28,23 @@ go install go.uber.org/mock/mockgen@latest
 
 ## Running mockgen
 
-`mockgen` has two modes of operation: source and reflect.
+`mockgen` has three modes of operation: archive, source and reflect.
+
+### Archive mode
+
+Archive mode generates mock interfaces from a package archive
+file (.a). It is enabled by using the -archive flag. An import
+path and a comma-separated list of symbols should be provided
+as a non-flag argument to the command.
+
+Example:
+
+```bash
+# Build the package to a archive.
+go build -o pkg.a database/sql/driver
+
+mockgen -archive=pkg.a database/sql/driver Conn,Driver
+```
 
 ### Source mode
 
@@ -66,6 +82,8 @@ The `mockgen` command is used to generate source code for a mock
 class given a Go source file containing interfaces to be mocked.
 It supports the following flags:
 
+- `-archive`: A package archive file containing interfaces to be mocked.
+
 - `-source`: A file containing interfaces to be mocked.
 
 - `-destination`: A file to which to write the resulting source code. If you

mockgen/archive.go

@@ -0,0 +1,55 @@
+package main
+
+import (
+	"fmt"
+	"go/token"
+	"go/types"
+	"os"
+
+	"go.uber.org/mock/mockgen/model"
+
+	"golang.org/x/tools/go/gcexportdata"
+)
+
+func archiveMode(importPath string, symbols []string, archive string) (*model.Package, error) {
+	f, err := os.Open(archive)
+	if err != nil {
+		return nil, err
+	}
+	defer f.Close()
+	r, err := gcexportdata.NewReader(f)
+	if err != nil {
+		return nil, fmt.Errorf("read export data %q: %v", archive, err)
+	}
+
+	fset := token.NewFileSet()
+	imports := make(map[string]*types.Package)
+	tp, err := gcexportdata.Read(r, fset, imports, importPath)
+	if err != nil {
+		return nil, err
+	}
+
+	pkg := &model.Package{
+		Name:       tp.Name(),
+		PkgPath:    tp.Path(),
+		Interfaces: make([]*model.Interface, 0, len(symbols)),
+	}
+	for _, name := range symbols {
+		m := tp.Scope().Lookup(name)
+		tn, ok := m.(*types.TypeName)
+		if !ok {
+			continue
+		}
+		ti, ok := tn.Type().Underlying().(*types.Interface)
+		if !ok {
+			continue
+		}
+		it, err := model.InterfaceFromGoTypesType(ti)
+		if err != nil {
+			return nil, err
+		}
+		it.Name = m.Name()
+		pkg.Interfaces = append(pkg.Interfaces, it)
+	}
+	return pkg, nil
+}

mockgen/mockgen.go

@@ -53,6 +53,7 @@ var (
 )
 
 var (
+	archive                = flag.String("archive", "", "(archive mode) Input Go archive file; enables archive mode.")
 	source                 = flag.String("source", "", "(source mode) Input Go source file; enables source mode.")
 	destination            = flag.String("destination", "", "Output file; defaults to stdout.")
 	mockNames              = flag.String("mock_names", "", "Comma-separated interfaceName=mockName pairs of explicit mock names to use. Mock names default to 'Mock'+ interfaceName suffix.")
@@ -66,9 +67,8 @@ var (
 	imports                = flag.String("imports", "", "(source mode) Comma-separated name=path pairs of explicit imports to use.")
 	auxFiles               = flag.String("aux_files", "", "(source mode) Comma-separated pkg=path pairs of auxiliary Go source files.")
 	excludeInterfaces      = flag.String("exclude_interfaces", "", "Comma-separated names of interfaces to be excluded")
-
-	debugParser = flag.Bool("debug_parser", false, "Print out parser results only.")
-	showVersion = flag.Bool("version", false, "Print version.")
+	debugParser            = flag.Bool("debug_parser", false, "Print out parser results only.")
+	showVersion            = flag.Bool("version", false, "Print version.")
 )
 
 func main() {
@@ -83,15 +83,22 @@ func main() {
 	var pkg *model.Package
 	var err error
 	var packageName string
-	if *source != "" {
+
+	// Switch between modes
+	switch {
+	case *source != "": // source mode
 		pkg, err = sourceMode(*source)
-	} else {
-		if flag.NArg() != 2 {
-			usage()
-			log.Fatal("Expected exactly two arguments")
-		}
+	case *archive != "": // archive mode
+		checkArgs()
+		packageName = flag.Arg(0)
+		interfaces := strings.Split(flag.Arg(1), ",")
+		pkg, err = archiveMode(packageName, interfaces, *archive)
+
+	default: // reflect mode
+		checkArgs()
 		packageName = flag.Arg(0)
 		interfaces := strings.Split(flag.Arg(1), ",")
+
 		if packageName == "." {
 			dir, err := os.Getwd()
 			if err != nil {
@@ -104,6 +111,7 @@ func main() {
 		}
 		pkg, err = reflectMode(packageName, interfaces)
 	}
+
 	if err != nil {
 		log.Fatalf("Loading input failed: %v", err)
 	}
@@ -144,6 +152,8 @@ func main() {
 	g := new(generator)
 	if *source != "" {
 		g.filename = *source
+	} else if *archive != "" {
+		g.filename = *archive
 	} else {
 		g.srcPackage = packageName
 		g.srcInterfaces = flag.Arg(1)
@@ -219,12 +229,19 @@ func parseExcludeInterfaces(names string) map[string]struct{} {
 	return namesSet
 }
 
+func checkArgs() {
+	if flag.NArg() != 2 {
+		usage()
+		log.Fatal("Expected exactly two arguments")
+	}
+}
+
 func usage() {
 	_, _ = io.WriteString(os.Stderr, usageText)
 	flag.PrintDefaults()
 }
 
-const usageText = `mockgen has two modes of operation: source and reflect.
+const usageText = `mockgen has three modes of operation: archive, source and reflect.
 
 Source mode generates mock interfaces from a source file.
 It is enabled by using the -source flag. Other flags that
@@ -239,6 +256,13 @@ comma-separated list of symbols.
 Example:
 	mockgen database/sql/driver Conn,Driver
 
+Archive mode generates mock interfaces from a package archive
+file (.a). It is enabled by using the -archive flag and two 
+non-flag arguments: an import path, and a comma-separated 
+list of symbols.
+Example:
+	mockgen -archive=pkg.a database/sql/driver Conn,Driver
+
 `
 
 type generator struct {

mockgen/model/model_gotypes.go

@@ -0,0 +1,160 @@
+package model
+
+import (
+	"fmt"
+	"go/types"
+)
+
+// InterfaceFromGoTypesType returns a pointer to an interface for the
+// given interface type loaded from archive.
+func InterfaceFromGoTypesType(it *types.Interface) (*Interface, error) {
+	intf := &Interface{}
+
+	for i := 0; i < it.NumMethods(); i++ {
+		mt := it.Method(i)
+		// Skip unexported methods.
+		if !mt.Exported() {
+			continue
+		}
+		m := &Method{
+			Name: mt.Name(),
+		}
+
+		var err error
+		m.In, m.Variadic, m.Out, err = funcArgsFromGoTypesType(mt.Type().(*types.Signature))
+		if err != nil {
+			return nil, fmt.Errorf("method %q: %w", mt.Name(), err)
+		}
+
+		intf.AddMethod(m)
+	}
+
+	return intf, nil
+}
+
+func funcArgsFromGoTypesType(t *types.Signature) (in []*Parameter, variadic *Parameter, out []*Parameter, err error) {
+	nin := t.Params().Len()
+	if t.Variadic() {
+		nin--
+	}
+	for i := 0; i < nin; i++ {
+		p, err := parameterFromGoTypesType(t.Params().At(i), false)
+		if err != nil {
+			return nil, nil, nil, err
+		}
+		in = append(in, p)
+	}
+	if t.Variadic() {
+		p, err := parameterFromGoTypesType(t.Params().At(nin), true)
+		if err != nil {
+			return nil, nil, nil, err
+		}
+		variadic = p
+	}
+	for i := 0; i < t.Results().Len(); i++ {
+		p, err := parameterFromGoTypesType(t.Results().At(i), false)
+		if err != nil {
+			return nil, nil, nil, err
+		}
+		out = append(out, p)
+	}
+	return
+}
+
+func parameterFromGoTypesType(v *types.Var, variadic bool) (*Parameter, error) {
+	t := v.Type()
+	if variadic {
+		t = t.(*types.Slice).Elem()
+	}
+	tt, err := typeFromGoTypesType(t)
+	if err != nil {
+		return nil, err
+	}
+	return &Parameter{Name: v.Name(), Type: tt}, nil
+}
+
+func typeFromGoTypesType(t types.Type) (Type, error) {
+	if t, ok := t.(*types.Named); ok {
+		tn := t.Obj()
+		if tn.Pkg() == nil {
+			return PredeclaredType(tn.Name()), nil
+		}
+		return &NamedType{
+			Package: tn.Pkg().Path(),
+			Type:    tn.Name(),
+		}, nil
+	}
+
+	// only unnamed or predeclared types after here
+
+	// Lots of types have element types. Let's do the parsing and error checking for all of them.
+	var elemType Type
+	if t, ok := t.(interface{ Elem() types.Type }); ok {
+		var err error
+		elemType, err = typeFromGoTypesType(t.Elem())
+		if err != nil {
+			return nil, err
+		}
+	}
+
+	switch t := t.(type) {
+	case *types.Array:
+		return &ArrayType{
+			Len:  int(t.Len()),
+			Type: elemType,
+		}, nil
+	case *types.Basic:
+		return PredeclaredType(t.String()), nil
+	case *types.Chan:
+		var dir ChanDir
+		switch t.Dir() {
+		case types.RecvOnly:
+			dir = RecvDir
+		case types.SendOnly:
+			dir = SendDir
+		}
+		return &ChanType{
+			Dir:  dir,
+			Type: elemType,
+		}, nil
+	case *types.Signature:
+		in, variadic, out, err := funcArgsFromGoTypesType(t)
+		if err != nil {
+			return nil, err
+		}
+		return &FuncType{
+			In:       in,
+			Out:      out,
+			Variadic: variadic,
+		}, nil
+	case *types.Interface:
+		if t.NumMethods() == 0 {
+			return PredeclaredType("interface{}"), nil
+		}
+	case *types.Map:
+		kt, err := typeFromGoTypesType(t.Key())
+		if err != nil {
+			return nil, err
+		}
+		return &MapType{
+			Key:   kt,
+			Value: elemType,
+		}, nil
+	case *types.Pointer:
+		return &PointerType{
+			Type: elemType,
+		}, nil
+	case *types.Slice:
+		return &ArrayType{
+			Len:  -1,
+			Type: elemType,
+		}, nil
+	case *types.Struct:
+		if t.NumFields() == 0 {
+			return PredeclaredType("struct{}"), nil
+		}
+		// TODO: UnsafePointer
+	}
+
+	return nil, fmt.Errorf("can't yet turn %v (%T) into a model.Type", t.String(), t)
+}