cmd/doc: perform type grouping for constants and variables

In golang.org/cl/22354, we added functionality to group functions under the
type that they construct to. In this CL, we extend the same concept to
constants and variables. This makes the doc tool more consistent with what
the godoc website does.

$ go doc reflect | egrep "ChanDir|Kind|SelectDir"
<<<
// Before:
const RecvDir ChanDir = 1 << iota ...
const Invalid Kind = iota ...
type ChanDir int
type Kind uint
type SelectDir int
    func ChanOf(dir ChanDir, t Type) Type

// After:
type ChanDir int
    const RecvDir ChanDir = 1 << iota ...
type Kind uint
    const Invalid Kind = iota ...
type SelectDir int
    const SelectSend SelectDir ...
    func ChanOf(dir ChanDir, t Type) Type
>>>

Furthermore, a fix was made to ensure that the type was printed in constant
blocks when the iota was applied on an unexported field.

$ go doc reflect SelectSend
<<<
// Before:
const (
	SelectSend    // case Chan <- Send
	SelectRecv    // case <-Chan:
	SelectDefault // default
)

// After:
const (
	SelectSend    SelectDir // case Chan <- Send
	SelectRecv              // case <-Chan:
	SelectDefault           // default
)
>>>

Fixes #16569

Change-Id: I26124c3d19e50caf9742bb936803a665e0fa6512
Reviewed-on: https://go-review.googlesource.com/25419
Reviewed-by: Rob Pike <r@golang.org>
Run-TryBot: Joe Tsai <thebrokentoaster@gmail.com>
TryBot-Result: Gobot Gobot <gobot@golang.org>

src/cmd/doc/pkg.go

@@ -211,27 +211,33 @@ func (pkg *Package) oneLineFunc(decl *ast.FuncDecl) {
 }
 
 // oneLineValueGenDecl prints a var or const declaration as a single line.
-func (pkg *Package) oneLineValueGenDecl(decl *ast.GenDecl) {
+func (pkg *Package) oneLineValueGenDecl(prefix string, decl *ast.GenDecl) {
 	decl.Doc = nil
 	dotDotDot := ""
 	if len(decl.Specs) > 1 {
 		dotDotDot = " ..."
 	}
 	// Find the first relevant spec.
+	typ := ""
 	for i, spec := range decl.Specs {
 		valueSpec := spec.(*ast.ValueSpec) // Must succeed; we can't mix types in one genDecl.
-		if !isExported(valueSpec.Names[0].Name) {
-			continue
-		}
-		typ := ""
+
+		// The type name may carry over from a previous specification in the
+		// case of constants and iota.
 		if valueSpec.Type != nil {
 			typ = fmt.Sprintf(" %s", pkg.formatNode(valueSpec.Type))
+		} else if len(valueSpec.Values) > 0 {
+			typ = ""
+		}
+
+		if !isExported(valueSpec.Names[0].Name) {
+			continue
 		}
 		val := ""
 		if i < len(valueSpec.Values) && valueSpec.Values[i] != nil {
 			val = fmt.Sprintf(" = %s", pkg.formatNode(valueSpec.Values[i]))
 		}
-		pkg.Printf("%s %s%s%s%s\n", decl.Tok, valueSpec.Names[0], typ, val, dotDotDot)
+		pkg.Printf("%s%s %s%s%s%s\n", prefix, decl.Tok, valueSpec.Names[0], typ, val, dotDotDot)
 		break
 	}
 }
@@ -266,8 +272,8 @@ func (pkg *Package) packageDoc() {
 	}
 
 	pkg.newlines(2) // Guarantee blank line before the components.
-	pkg.valueSummary(pkg.doc.Consts)
-	pkg.valueSummary(pkg.doc.Vars)
+	pkg.valueSummary(pkg.doc.Consts, false)
+	pkg.valueSummary(pkg.doc.Vars, false)
 	pkg.funcSummary(pkg.doc.Funcs, false)
 	pkg.typeSummary()
 	pkg.bugs()
@@ -302,9 +308,29 @@ func (pkg *Package) packageClause(checkUserPath bool) {
 }
 
 // valueSummary prints a one-line summary for each set of values and constants.
-func (pkg *Package) valueSummary(values []*doc.Value) {
+// If all the types in a constant or variable declaration belong to the same
+// type they can be printed by typeSummary, and so can be suppressed here.
+func (pkg *Package) valueSummary(values []*doc.Value, showGrouped bool) {
+	var isGrouped map[*doc.Value]bool
+	if !showGrouped {
+		isGrouped = make(map[*doc.Value]bool)
+		for _, typ := range pkg.doc.Types {
+			if !isExported(typ.Name) {
+				continue
+			}
+			for _, c := range typ.Consts {
+				isGrouped[c] = true
+			}
+			for _, v := range typ.Vars {
+				isGrouped[v] = true
+			}
+		}
+	}
+
 	for _, value := range values {
-		pkg.oneLineValueGenDecl(value.Decl)
+		if !isGrouped[value] {
+			pkg.oneLineValueGenDecl("", value.Decl)
+		}
 	}
 }
 
@@ -316,10 +342,11 @@ func (pkg *Package) funcSummary(funcs []*doc.Func, showConstructors bool) {
 	if !showConstructors {
 		isConstructor = make(map[*doc.Func]bool)
 		for _, typ := range pkg.doc.Types {
-			for _, constructor := range typ.Funcs {
-				if isExported(typ.Name) {
-					isConstructor[constructor] = true
-				}
+			if !isExported(typ.Name) {
+				continue
+			}
+			for _, f := range typ.Funcs {
+				isConstructor[f] = true
 			}
 		}
 	}
@@ -341,7 +368,13 @@ func (pkg *Package) typeSummary() {
 			typeSpec := spec.(*ast.TypeSpec) // Must succeed.
 			if isExported(typeSpec.Name.Name) {
 				pkg.oneLineTypeDecl(typeSpec)
-				// Now print the constructors.
+				// Now print the consts, vars, and constructors.
+				for _, c := range typ.Consts {
+					pkg.oneLineValueGenDecl(indent, c.Decl)
+				}
+				for _, v := range typ.Vars {
+					pkg.oneLineValueGenDecl(indent, v.Decl)
+				}
 				for _, constructor := range typ.Funcs {
 					if isExported(constructor.Name) {
 						pkg.Printf(indent)
@@ -437,11 +470,29 @@ func (pkg *Package) symbolDoc(symbol string) bool {
 		// It's an unlikely scenario, probably not worth the trouble.
 		// TODO: Would be nice if go/doc did this for us.
 		specs := make([]ast.Spec, 0, len(value.Decl.Specs))
+		var typ ast.Expr
 		for _, spec := range value.Decl.Specs {
 			vspec := spec.(*ast.ValueSpec)
+
+			// The type name may carry over from a previous specification in the
+			// case of constants and iota.
+			if vspec.Type != nil {
+				typ = vspec.Type
+			}
+
 			for _, ident := range vspec.Names {
 				if isExported(ident.Name) {
+					if vspec.Type == nil && vspec.Values == nil && typ != nil {
+						// This a standalone identifier, as in the case of iota usage.
+						// Thus, assume the type comes from the previous type.
+						vspec.Type = &ast.Ident{
+							Name:    string(pkg.formatNode(typ)),
+							NamePos: vspec.End() - 1,
+						}
+					}
+
 					specs = append(specs, vspec)
+					typ = nil // Only inject type on first exported identifier
 					break
 				}
 			}
@@ -473,8 +524,8 @@ func (pkg *Package) symbolDoc(symbol string) bool {
 		if len(typ.Consts) > 0 || len(typ.Vars) > 0 || len(typ.Funcs) > 0 || len(typ.Methods) > 0 {
 			pkg.Printf("\n")
 		}
-		pkg.valueSummary(typ.Consts)
-		pkg.valueSummary(typ.Vars)
+		pkg.valueSummary(typ.Consts, true)
+		pkg.valueSummary(typ.Vars, true)
 		pkg.funcSummary(typ.Funcs, true)
 		pkg.funcSummary(typ.Methods, true)
 		found = true