Change https://go.dev/cl/523059 mentions this issue: internal/godoc/dochtml/internal/render: fix linking of interface methods

Hey guys

I just note that links to public methods in a public interface are not linked correctly via godoc if it refers to the same package. Same for public fields:

notable examples

link to public method in type interface

https://pkg.go.dev/encoding/json@go1.22.4#MarshalerError

A MarshalerError represents an error from calling a [Marshaler.MarshalJSON] or encoding.TextMarshaler.MarshalText method.

// A MarshalerError represents an error from calling a
// [Marshaler.MarshalJSON] or [encoding.TextMarshaler.MarshalText] method.
type MarshalerError struct {

The rendering:

[Marshaler.MarshalJSON] does not work, expected https://pkg.go.dev/encoding/json#Marshaler.MarshalJSON

[encoding.TextMarshaler.MarshalText] => work as expected, became https://pkg.go.dev/encoding#TextMarshaler.MarshalText

Another example: https://pkg.go.dev/io@go1.22.4#WriteString

link to public field in type struct

https://pkg.go.dev/archive/tar@go1.22.4#Reader.Read

// Calling Read on special types like [TypeLink], [TypeSymlink], [TypeChar],
// [TypeBlock], [TypeDir], and [TypeFifo] returns (0, [io.EOF]) regardless of what
// the [Header.Size] claims.
func (tr *Reader) Read(b []byte) (int, error) {

Calling Read on special types like TypeLink, TypeSymlink, TypeChar, TypeBlock, TypeDir, and TypeFifo returns (0, io.EOF) regardless of what the [Header.Size] claims.

The rendering:

[Header.Size] does not work, expected https://pkg.go.dev/archive/tar#Header.Size

I can't find an example, but I think it may work from another package, like the previous issue in the public interface

link to builtin function defined on the current package:

https://pkg.go.dev/builtin@go1.22.4#recover

Prior to Go 1.21, recover would also return nil if panic is called with a nil argument. See [panic] for details.

The rendering:

[panic] does not work, expected https://pkg.go.dev/builtin@go1.22.4#panic

let me ask: this issue #62293 also refer to such errors? or should I open another ticket?

This is kinda annoying BTW

There is a duplicate #63679

It is unclear how to best fix this. Ideally interface methods appear in Type.Methods, but historically they have not.
Adding them in there could break tools that are not expecting their appearance.

Alternatively, to fix links it should be enough to add interface methods into p.syms like:

index 4d01ae458b..192554ec2b 100644
--- a/src/go/doc/doc.go
+++ b/src/go/doc/doc.go
@@ -167,6 +167,7 @@ func (p *Package) collectTypes(types []*Type) {
                p.collectValues(t.Vars)
                p.collectFuncs(t.Funcs)
                p.collectFuncs(t.Methods)
+               p.collectInterfaceMethods(t)
        }
 }
 
@@ -184,6 +185,21 @@ func (p *Package) collectFuncs(funcs []*Func) {
        }
 }
 
+func (p *Package) collectInterfaceMethods(t *Type) {
+       if t.Decl != nil && t.Decl.Tok == token.TYPE {
+               for _, s := range t.Decl.Specs {
+                       s := s.(*ast.TypeSpec) // token.TYPE guarantees this
+                       if i, ok := s.Type.(*ast.InterfaceType); ok {
+                               for _, m := range i.Methods.List {
+                                       if len(m.Names) > 0 { // skip embedded interfaces
+                                               p.syms[t.Name+"."+m.Names[0].Name] = true
+                                       }
+                               }
+                       }
+               }
+       }
+}
+

Related to #54033