go/doc: inspect function signature for building playground examples

This documentation example was broken:
https://golang.org/pkg/image/png/#example_Decode.
It did not have the "io" package imported,
The package was referenced in the result type of the function.

The "playExample" function did not inspect
the result types of declared functions.

This CL adds inspecting of parameters and result types of functions.

Fixes #28492
Updates #9679

Change-Id: I6d8b11bad2db8ea8ba69039cfaa914093bdd5132
Reviewed-on: https://go-review.googlesource.com/c/146118
Run-TryBot: Yury Smolsky <yury@smolsky.by>
TryBot-Result: Gobot Gobot <gobot@golang.org>
Reviewed-by: Robert Griesemer <gri@golang.org>

diff --git a/src/go/doc/example.go b/src/go/doc/example.go
index d6d4ece3a8e39b0e42611c86a7f776e0b6daf3ac..cf3547810ad1bebd7863ffbff3a4814c1c047455 100644 (file)
--- a/src/go/doc/example.go
+++ b/src/go/doc/example.go
@@ -219,6 +219,18 @@ func playExample(file *ast.File, f *ast.FuncDecl) *ast.File {
        for i := 0; i < len(depDecls); i++ {
                switch d := depDecls[i].(type) {
                case *ast.FuncDecl:
+                       // Inspect types of parameters and results. See #28492.
+                       if d.Type.Params != nil {
+                               for _, p := range d.Type.Params.List {
+                                       ast.Inspect(p.Type, inspectFunc)
+                               }
+                       }
+                       if d.Type.Results != nil {
+                               for _, r := range d.Type.Results.List {
+                                       ast.Inspect(r.Type, inspectFunc)
+                               }
+                       }
+
                        ast.Inspect(d.Body, inspectFunc)
                case *ast.GenDecl:
                        for _, spec := range d.Specs {

diff --git a/src/go/doc/example_test.go b/src/go/doc/example_test.go
index 552a51bf742192a4659aeb7b2bdd236bf42297ce..0d2bf72e319b6e5ecbeb4b250b60b9abdf7f4a4b 100644 (file)
--- a/src/go/doc/example_test.go
+++ b/src/go/doc/example_test.go
@@ -351,6 +351,68 @@ func TestExamplesWholeFile(t *testing.T) {
        }
 }
 
+const exampleInspectSignature = `package foo_test
+
+import (
+       "bytes"
+       "io"
+)
+
+func getReader() io.Reader { return nil }
+
+func do(b bytes.Reader) {}
+
+func Example() {
+       getReader()
+       do()
+       // Output:
+}
+
+func ExampleIgnored() {
+}
+`
+
+const exampleInspectSignatureOutput = `package main
+
+import (
+       "bytes"
+       "io"
+)
+
+func getReader() io.Reader { return nil }
+
+func do(b bytes.Reader) {}
+
+func main() {
+       getReader()
+       do()
+}
+`
+
+func TestExampleInspectSignature(t *testing.T) {
+       // Verify that "bytes" and "io" are imported. See issue #28492.
+       fset := token.NewFileSet()
+       file, err := parser.ParseFile(fset, "test.go", strings.NewReader(exampleInspectSignature), parser.ParseComments)
+       if err != nil {
+               t.Fatal(err)
+       }
+       es := doc.Examples(file)
+       if len(es) != 2 {
+               t.Fatalf("wrong number of examples; got %d want 2", len(es))
+       }
+       // We are interested in the first example only.
+       e := es[0]
+       if e.Name != "" {
+               t.Errorf("got Name == %q, want %q", e.Name, "")
+       }
+       if g, w := formatFile(t, fset, e.Play), exampleInspectSignatureOutput; g != w {
+               t.Errorf("got Play == %q, want %q", g, w)
+       }
+       if g, w := e.Output, ""; g != w {
+               t.Errorf("got Output == %q, want %q", g, w)
+       }
+}
+
 func formatFile(t *testing.T, fset *token.FileSet, n *ast.File) string {
        if n == nil {
                return "<nil>"