goose: use readable variable names

Names are inferred from types most of the time, but have a fallback for
a non-named type. Names are now also disambiguated from symbols in the
same scope.

Reviewed-by: Tuo Shan <shantuo@google.com>
Reviewed-by: Herbie Ong <herbie@google.com>

README.md

@@ -208,9 +208,6 @@ type MySQLConnectionString string
 
 ## Future Work
 
--   The names of imports and provider results in the generated code are not
-    actually as nice as shown above. I'd like to make them nicer in the
-    common cases while ensuring uniqueness.
 -   Support for map bindings.
 -   Support for multiple provider outputs.
 -   Currently, all dependency satisfaction is done using identity. I'd like to

internal/goose/goose.go

@@ -14,6 +14,8 @@ import (
 	"sort"
 	"strconv"
 	"strings"
+	"unicode"
+	"unicode/utf8"
 
 	"golang.org/x/tools/go/loader"
 	"golang.org/x/tools/go/types/typeutil"
@@ -43,13 +45,14 @@ func Generate(bctx *build.Context, wd string, pkg string) ([]byte, error) {
 		return nil, fmt.Errorf("load: got %d packages", len(prog.InitialPackages()))
 	}
 	pkgInfo := prog.InitialPackages()[0]
-	g := newGen(pkgInfo.Pkg.Path())
+	g := newGen(prog, pkgInfo.Pkg.Path())
 	mc := newProviderSetCache(prog)
 	var directives []directive
 	for _, f := range pkgInfo.Files {
 		if !isInjectFile(f) {
 			continue
 		}
+		// TODO(light): use same directive extraction logic as provider set finding.
 		fileScope := pkgInfo.Scopes[f]
 		cmap := ast.NewCommentMap(prog.Fset, f, f.Comments)
 		for _, decl := range f.Decls {
@@ -78,7 +81,7 @@ func Generate(bctx *build.Context, wd string, pkg string) ([]byte, error) {
 			}
 		}
 	}
-	goSrc := g.frame(pkgInfo.Pkg.Name())
+	goSrc := g.frame()
 	fmtSrc, err := format.Source(goSrc)
 	if err != nil {
 		// This is likely a bug from a poorly generated source file.
@@ -93,24 +96,25 @@ type gen struct {
 	currPackage string
 	buf         bytes.Buffer
 	imports     map[string]string
-	n           int
+	prog        *loader.Program // for determining package names
 }
 
-func newGen(pkg string) *gen {
+func newGen(prog *loader.Program, pkg string) *gen {
 	return &gen{
 		currPackage: pkg,
 		imports:     make(map[string]string),
+		prog:        prog,
 	}
 }
 
 // frame bakes the built up source body into an unformatted Go source file.
-func (g *gen) frame(pkgName string) []byte {
+func (g *gen) frame() []byte {
 	if g.buf.Len() == 0 {
 		return nil
 	}
 	var buf bytes.Buffer
 	buf.WriteString("// Code generated by goose. DO NOT EDIT.\n\n//+build !gooseinject\n\npackage ")
-	buf.WriteString(pkgName)
+	buf.WriteString(g.prog.Package(g.currPackage).Pkg.Name())
 	buf.WriteString("\n\n")
 	if len(g.imports) > 0 {
 		buf.WriteString("import (\n")
@@ -120,6 +124,8 @@ func (g *gen) frame(pkgName string) []byte {
 		}
 		sort.Strings(imps)
 		for _, path := range imps {
+			// TODO(light): Omit the local package identifier if it matches
+			// the package name.
 			fmt.Fprintf(&buf, "\t%s %q\n", g.imports[path], path)
 		}
 		buf.WriteString(")\n\n")
@@ -160,25 +166,71 @@ func (g *gen) inject(mc *providerSetCache, name string, sig *types.Signature, se
 			return fmt.Errorf("inject %s: provider for %s returns error but injection not allowed to fail", name, types.TypeString(calls[i].out, nil))
 		}
 	}
+
+	// Prequalify all types.  Since import disambiguation ignores local
+	// variables, it takes precedence.
+	paramTypes := make([]string, params.Len())
+	for i := 0; i < params.Len(); i++ {
+		paramTypes[i] = types.TypeString(params.At(i).Type(), g.qualifyPkg)
+	}
+	for _, c := range calls {
+		g.qualifyImport(c.importPath)
+	}
+	outTypeString := types.TypeString(outType, g.qualifyPkg)
+	zv := zeroValue(outType, g.qualifyPkg)
+	// Set up local variables
+	paramNames := make([]string, params.Len())
+	localNames := make([]string, len(calls))
+	errVar := disambiguate("err", g.nameInFileScope)
+	collides := func(v string) bool {
+		if v == errVar {
+			return true
+		}
+		for _, a := range paramNames {
+			if a == v {
+				return true
+			}
+		}
+		for _, l := range localNames {
+			if l == v {
+				return true
+			}
+		}
+		return g.nameInFileScope(v)
+	}
+
 	g.p("func %s(", name)
 	for i := 0; i < params.Len(); i++ {
 		if i > 0 {
 			g.p(", ")
 		}
 		pi := params.At(i)
-		g.p("%s %s", pi.Name(), types.TypeString(pi.Type(), g.qualifyPkg))
+		a := pi.Name()
+		if a == "" || a == "_" {
+			a = typeVariableName(pi.Type())
+			if a == "" {
+				a = "arg"
+			}
+		}
+		paramNames[i] = disambiguate(a, collides)
+		g.p("%s %s", paramNames[i], paramTypes[i])
 	}
 	if returnsErr {
-		g.p(") (%s, error) {\n", types.TypeString(outType, g.qualifyPkg))
+		g.p(") (%s, error) {\n", outTypeString)
 	} else {
-		g.p(") %s {\n", types.TypeString(outType, g.qualifyPkg))
+		g.p(") %s {\n", outTypeString)
 	}
-	zv := zeroValue(outType, g.qualifyPkg)
 	for i := range calls {
 		c := &calls[i]
-		g.p("\tv%d", i)
+		lname := typeVariableName(c.out)
+		if lname == "" {
+			lname = "v"
+		}
+		lname = disambiguate(lname, collides)
+		localNames[i] = lname
+		g.p("\t%s", lname)
 		if c.hasErr {
-			g.p(", err")
+			g.p(", %s", errVar)
 		}
 		g.p(" := %s(", g.qualifiedID(c.importPath, c.funcName))
 		for j, a := range c.args {
@@ -186,14 +238,14 @@ func (g *gen) inject(mc *providerSetCache, name string, sig *types.Signature, se
 				g.p(", ")
 			}
 			if a < params.Len() {
-				g.p("%s", params.At(a).Name())
+				g.p("%s", paramNames[a])
 			} else {
-				g.p("v%d", a-params.Len())
+				g.p("%s", localNames[a-params.Len()])
 			}
 		}
 		g.p(")\n")
 		if c.hasErr {
-			g.p("\tif err != nil {\n")
+			g.p("\tif %s != nil {\n", errVar)
 			// TODO(light): give information about failing provider
 			g.p("\t\treturn %s, err\n", zv)
 			g.p("\t}\n")
@@ -202,12 +254,12 @@ func (g *gen) inject(mc *providerSetCache, name string, sig *types.Signature, se
 	if len(calls) == 0 {
 		for i := range given {
 			if types.Identical(outType, given[i]) {
-				g.p("\treturn %s", params.At(i).Name())
+				g.p("\treturn %s", paramNames[i])
 				break
 			}
 		}
 	} else {
-		g.p("\treturn v%d", len(calls)-1)
+		g.p("\treturn %s", localNames[len(calls)-1])
 	}
 	if returnsErr {
 		g.p(", nil")
@@ -231,12 +283,25 @@ func (g *gen) qualifyImport(path string) string {
 	if name := g.imports[path]; name != "" {
 		return name
 	}
-	name := fmt.Sprintf("pkg%d", g.n)
-	g.n++
+	// TODO(light): use parts of import path to disambiguate.
+	name := disambiguate(g.prog.Package(path).Pkg.Name(), func(n string) bool {
+		// Don't let an import take the "err" name. That's annoying.
+		return n == "err" || g.nameInFileScope(n)
+	})
 	g.imports[path] = name
 	return name
 }
 
+func (g *gen) nameInFileScope(name string) bool {
+	for _, other := range g.imports {
+		if other == name {
+			return true
+		}
+	}
+	_, obj := g.prog.Package(g.currPackage).Pkg.Scope().LookupParent(name, 0)
+	return obj != nil
+}
+
 func (g *gen) qualifyPkg(pkg *types.Package) string {
 	return g.qualifyImport(pkg.Path())
 }
@@ -418,12 +483,8 @@ func (mc *providerSetCache) get(ref providerSetRef) (*providerSet, error) {
 	if mc.sets == nil {
 		mc.sets = make(map[string]map[string]*providerSet)
 	}
-	pkg, info, files, err := mc.getpkg(ref.importPath)
-	if err != nil {
-		mc.sets[ref.importPath] = nil
-		return nil, fmt.Errorf("analyze package: %v", err)
-	}
-	mods, err := findProviderSets(mc.fset, pkg, info, files)
+	pkg := mc.prog.Package(ref.importPath)
+	mods, err := findProviderSets(mc.fset, pkg.Pkg, &pkg.Info, pkg.Files)
 	if err != nil {
 		mc.sets[ref.importPath] = nil
 		return nil, err
@@ -436,16 +497,6 @@ func (mc *providerSetCache) get(ref providerSetRef) (*providerSet, error) {
 	return mod, nil
 }
 
-func (mc *providerSetCache) getpkg(path string) (*types.Package, *types.Info, []*ast.File, error) {
-	// TODO(light): allow other implementations for testing
-
-	pkg := mc.prog.Package(path)
-	if pkg == nil {
-		return nil, nil, nil, fmt.Errorf("package %q not found", path)
-	}
-	return pkg.Pkg, &pkg.Info, pkg.Files, nil
-}
-
 // solve finds the sequence of calls required to produce an output type
 // with an optional set of provided inputs.
 func solve(mc *providerSetCache, out types.Type, given []types.Type, sets []providerSetRef) ([]call, error) {
@@ -708,4 +759,67 @@ func zeroValue(t types.Type, qf types.Qualifier) string {
 	}
 }
 
+// typeVariableName invents a variable name derived from the type name
+// or returns the empty string if one could not be found.
+func typeVariableName(t types.Type) string {
+	if p, ok := t.(*types.Pointer); ok {
+		t = p.Elem()
+	}
+	tn, ok := t.(*types.Named)
+	if !ok {
+		return ""
+	}
+	// TODO(light): include package name when appropriate
+	return unexport(tn.Obj().Name())
+}
+
+// unexport converts a name that is potentially exported to an unexported name.
+func unexport(name string) string {
+	r, sz := utf8.DecodeRuneInString(name)
+	if !unicode.IsUpper(r) {
+		// foo -> foo
+		return name
+	}
+	r2, sz2 := utf8.DecodeRuneInString(name[sz:])
+	if !unicode.IsUpper(r2) {
+		// Foo -> foo
+		return string(unicode.ToLower(r)) + name[sz:]
+	}
+	// UPPERWord -> upperWord
+	sbuf := new(strings.Builder)
+	sbuf.WriteRune(unicode.ToLower(r))
+	i := sz
+	r, sz = r2, sz2
+	for unicode.IsUpper(r) && sz > 0 {
+		r2, sz2 := utf8.DecodeRuneInString(name[i+sz:])
+		if sz2 > 0 && unicode.IsLower(r2) {
+			break
+		}
+		i += sz
+		sbuf.WriteRune(unicode.ToLower(r))
+		r, sz = r2, sz2
+	}
+	sbuf.WriteString(name[i:])
+	return sbuf.String()
+}
+
+// disambiguate picks a unique name, preferring name if it is already unique.
+func disambiguate(name string, collides func(string) bool) string {
+	if !collides(name) {
+		return name
+	}
+	buf := []byte(name)
+	if len(buf) > 0 && buf[len(buf)-1] >= '0' && buf[len(buf)-1] <= '9' {
+		buf = append(buf, '_')
+	}
+	base := len(buf)
+	for n := 2; ; n++ {
+		buf = strconv.AppendInt(buf[:base], int64(n), 10)
+		sbuf := string(buf)
+		if !collides(sbuf) {
+			return sbuf
+		}
+	}
+}
+
 var errorType = types.Universe.Lookup("error").Type()

internal/goose/goose_test.go

@@ -15,6 +15,8 @@ import (
 	"strings"
 	"testing"
 	"time"
+	"unicode"
+	"unicode/utf8"
 )
 
 func TestGoose(t *testing.T) {
@@ -130,6 +132,83 @@ func TestGoose(t *testing.T) {
 	})
 }
 
+func TestUnexport(t *testing.T) {
+	tests := []struct {
+		name string
+		want string
+	}{
+		{"a", "a"},
+		{"ab", "ab"},
+		{"A", "a"},
+		{"AB", "ab"},
+		{"A_", "a_"},
+		{"ABc", "aBc"},
+		{"ABC", "abc"},
+		{"AB_", "ab_"},
+		{"foo", "foo"},
+		{"Foo", "foo"},
+		{"HTTPClient", "httpClient"},
+		{"IFace", "iFace"},
+		{"SNAKE_CASE", "snake_CASE"},
+		{"HTTP", "http"},
+	}
+	for _, test := range tests {
+		if got := unexport(test.name); got != test.want {
+			t.Errorf("unexport(%q) = %q; want %q", test.name, got, test.want)
+		}
+	}
+}
+
+func TestDisambiguate(t *testing.T) {
+	tests := []struct {
+		name     string
+		collides map[string]bool
+	}{
+		{"foo", nil},
+		{"foo", map[string]bool{"foo": true}},
+		{"foo", map[string]bool{"foo": true, "foo1": true, "foo2": true}},
+		{"foo1", map[string]bool{"foo": true, "foo1": true, "foo2": true}},
+		{"foo\u0661", map[string]bool{"foo": true, "foo1": true, "foo2": true}},
+		{"foo\u0661", map[string]bool{"foo": true, "foo1": true, "foo2": true, "foo\u0661": true}},
+	}
+	for _, test := range tests {
+		got := disambiguate(test.name, func(name string) bool { return test.collides[name] })
+		if !isIdent(got) {
+			t.Errorf("disambiguate(%q, %v) = %q; not an identifier", test.name, test.collides, got)
+		}
+		if test.collides[got] {
+			t.Errorf("disambiguate(%q, %v) = %q; ", test.name, test.collides, got)
+		}
+	}
+}
+
+func isIdent(s string) bool {
+	if len(s) == 0 {
+		if s == "foo" {
+			panic("BREAK3")
+		}
+		return false
+	}
+	r, i := utf8.DecodeRuneInString(s)
+	if !unicode.IsLetter(r) && r != '_' {
+		if s == "foo" {
+			panic("BREAK2")
+		}
+		return false
+	}
+	for i < len(s) {
+		r, sz := utf8.DecodeRuneInString(s[i:])
+		if !unicode.IsLetter(r) && !unicode.IsDigit(r) && r != '_' {
+			if s == "foo" {
+				panic("BREAK1")
+			}
+			return false
+		}
+		i += sz
+	}
+	return true
+}
+
 type testCase struct {
 	name       string
 	pkg        string

internal/goose/testdata/NamingWorstCase/foo/foo.go

@@ -0,0 +1,24 @@
+package main
+
+import (
+	stdcontext "context"
+	"fmt"
+	"os"
+)
+
+type context struct{}
+
+func main() {
+	c, err := inject(stdcontext.Background(), struct{}{})
+	if err != nil {
+		fmt.Println("ERROR:", err)
+		os.Exit(1)
+	}
+	fmt.Println(c)
+}
+
+//goose:provide
+
+func provide(ctx stdcontext.Context) (context, error) {
+	return context{}, nil
+}

internal/goose/testdata/NamingWorstCase/foo/goose.go

@@ -0,0 +1,11 @@
+//+build gooseinject
+
+package main
+
+import (
+	stdcontext "context"
+)
+
+//goose:use provide
+
+func inject(context stdcontext.Context, err struct{}) (context, error)

internal/goose/testdata/NamingWorstCase/out.txt

@@ -0,0 +1 @@
+{}

internal/goose/testdata/NamingWorstCase/pkg

@@ -0,0 +1 @@
+foo

internal/goose/testdata/NoInjectParamNames/foo/foo.go

@@ -0,0 +1,24 @@
+package main
+
+import (
+	stdcontext "context"
+	"fmt"
+	"os"
+)
+
+type context struct{}
+
+func main() {
+	c, err := inject(stdcontext.Background(), struct{}{})
+	if err != nil {
+		fmt.Println("ERROR:", err)
+		os.Exit(1)
+	}
+	fmt.Println(c)
+}
+
+//goose:provide
+
+func provide(ctx stdcontext.Context) (context, error) {
+	return context{}, nil
+}

internal/goose/testdata/NoInjectParamNames/foo/goose.go

@@ -0,0 +1,14 @@
+//+build gooseinject
+
+package main
+
+import (
+	stdcontext "context"
+)
+
+// The notable characteristic of this test is that there are no
+// parameter names on the inject stub.
+
+//goose:use provide
+
+func inject(stdcontext.Context, struct{}) (context, error)

internal/goose/testdata/NoInjectParamNames/out.txt

@@ -0,0 +1 @@
+{}

internal/goose/testdata/NoInjectParamNames/pkg

@@ -0,0 +1 @@
+foo