goose: use function name as implicit provider set

Single-element provider sets are frequently useful enough to warrant
being a default.  Larger groupings within a package are less frequent.

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

README.md

@@ -31,7 +31,7 @@ func ProvideFoo() Foo {
 
 Providers are always part of a **provider set**: if there is no provider set
 named on the `//goose:provide` line, then the provider is added to the provider
-set with the name `Module`.
+set with the same name as the function (`ProvideFoo`, in this case).
 
 Providers can specify dependencies with parameters:
 
@@ -71,11 +71,11 @@ func ProvideBaz(ctx context.Context, bar Bar) (Baz, error) {
 }
 ```
 
-Provider sets can import other provider sets.  To add `Module` in
+Provider sets can import other provider sets.  To add the `ProvideFoo` set to
 `SuperSet`:
 
 ```go
-// goose:import SuperSet Module
+// goose:import SuperSet ProvideFoo
 ```
 
 You can also import provider sets in another package, provided that you have a

internal/goose/goose.go

@@ -256,8 +256,6 @@ type providerSetImport struct {
 	pos token.Pos
 }
 
-const implicitModuleName = "Module"
-
 // findProviderSets processes a package and extracts the provider sets declared in it.
 func findProviderSets(fset *token.FileSet, pkg *types.Package, typeInfo *types.Info, files []*ast.File) (map[string]*providerSet, error) {
 	sets := make(map[string]*providerSet)
@@ -274,14 +272,12 @@ func findProviderSets(fset *token.FileSet, pkg *types.Package, typeInfo *types.I
 					if fileScope == nil {
 						return nil, fmt.Errorf("%s: no scope found for file (likely a bug)", fset.File(f.Pos()).Name())
 					}
-					var name, spec string
+					i := strings.IndexByte(d.line, ' ')
-					if strings.HasPrefix(d.line, `"`) {
+					// TODO(light): allow multiple imports in one line
-						name, spec = implicitModuleName, d.line
+					if i == -1 {
-					} else if i := strings.IndexByte(d.line, ' '); i != -1 {
+						return nil, fmt.Errorf("%s: invalid import: expected TARGET SETREF", fset.Position(d.pos))
-						name, spec = d.line[:i], d.line[i+1:]
-					} else {
-						name, spec = implicitModuleName, d.line
 					}
+					name, spec := d.line[:i], d.line[i+1:]
 					ref, err := parseProviderSetRef(spec, fileScope, pkg.Path(), d.pos)
 					if err != nil {
 						return nil, fmt.Errorf("%v: %v", fset.Position(d.pos), err)
@@ -337,9 +333,8 @@ func findProviderSets(fset *token.FileSet, pkg *types.Package, typeInfo *types.I
 				if !isFunction {
 					return nil, fmt.Errorf("%v: only functions can be marked as providers", fset.Position(d.pos))
 				}
-				if d.line == "" {
+				providerSetName = fn.Name.Name
-					providerSetName = implicitModuleName
+				if d.line != "" {
-				} else {
 					// TODO(light): validate identifier
 					providerSetName = d.line
 				}

internal/goose/goose_test.go

@@ -44,7 +44,7 @@ func provideMessage() string { return "Hello, World!"; }
 
 package main
 
-//goose:use Module
+//goose:use provideMessage
 
 func injectedMessage() string
 `,
@@ -59,7 +59,7 @@ func injectedMessage() string
 import "fmt"
 func main() { fmt.Println(injectedMessage()); }
 
-//goose:provide
+//goose:provide Set
 
 // provideMessage provides a friendly user greeting.
 func provideMessage() string { return "Hello, World!"; }
@@ -86,17 +86,17 @@ func main() {
 type Foo int
 type FooBar int
 
-//goose:provide
+//goose:provide Set
 func provideFoo() Foo { return 41 }
 
-//goose:provide
+//goose:provide Set
 func provideFooBar(foo Foo) FooBar { return FooBar(foo) + 1 }
 `,
 			"foo/foo_goose.go": `//+build gooseinject
 
 package main
 
-//goose:use Module
+//goose:use Set
 
 func injectFooBar() FooBar
 `,
@@ -117,20 +117,20 @@ type Foo int
 type Bar int
 type FooBar int
 
-//goose:provide
+//goose:provide Set
 func provideFoo() Foo { return 40 }
 
-//goose:provide
+//goose:provide Set
 func provideBar() Bar { return 2 }
 
-//goose:provide
+//goose:provide Set
 func provideFooBar(foo Foo, bar Bar) FooBar { return FooBar(foo) + FooBar(bar) }
 `,
 			"foo/foo_goose.go": `//+build gooseinject
 
 package main
 
-//goose:use Module
+//goose:use Set
 
 func injectFooBar() FooBar
 `,
@@ -151,17 +151,17 @@ type Foo int
 type Bar int
 type FooBar int
 
-//goose:provide
+//goose:provide Set
 func provideBar() Bar { return 2 }
 
-//goose:provide
+//goose:provide Set
 func provideFooBar(foo Foo, bar Bar) FooBar { return FooBar(foo) + FooBar(bar) }
 `,
 			"foo/foo_goose.go": `//+build gooseinject
 
 package main
 
-//goose:use Module
+//goose:use Set
 
 func injectFooBar(foo Foo) FooBar
 `,
@@ -181,17 +181,17 @@ func main() {
 type Foo int
 type Bar int
 
-//goose:provide
+//goose:provide Set
 func provideFoo() Foo { return -888 }
 
-//goose:provide
+//goose:provide Set
 func provideBar(foo Foo) Bar { return 2 }
 `,
 			"foo/foo_goose.go": `//+build gooseinject
 
 package main
 
-//goose:use Module
+//goose:use Set
 
 func injectBar(foo Foo) Bar
 `,
@@ -218,14 +218,14 @@ func main() {
 
 type Foo int
 
-//goose:provide
+//goose:provide Set
 func provideFoo() (Foo, error) { return 42, errors.New("there is no Foo") }
 `,
 			"foo/foo_goose.go": `//+build gooseinject
 
 package main
 
-//goose:use Module
+//goose:use Set
 
 func injectFoo() (Foo, error)
 `,