Source: symbol.go in package golang.org/x/pkgsite/internal/frontend


package frontend

import (
	"fmt"
	"sort"
	"strings"

	"golang.org/x/pkgsite/internal"
	"golang.org/x/pkgsite/internal/stdlib"
)

Symbol is an element in the package API. A symbol can be a constant, variable, function, type, field or method.

Name is name of the symbol. At a given package version, name must be unique.

	Name string

Synopsis is the one line description of the symbol that is displayed.

	Synopsis string

Section is the section that a symbol appears in.

	Section internal.SymbolSection

Kind is the type of a symbol, which is either a constant, variable, function, type, field or method.

	Kind internal.SymbolKind

Link is the link to the symbol name on pkg.go.dev.

	Link string

Children contain the child symbols for this symbol. This will only be populated when the SymbolType is "Type". For example, the children of net/http.Handler are FileServer, NotFoundHandler, RedirectHandler, StripPrefix, and TimeoutHandler. Each child symbol will have ParentName set to the Name of this type.

	Children []*Symbol

Builds lists all of the build contexts supported by the symbol, it is only available for limited set of builds. If the symbol supports all build contexts, Builds will be nil.

	Builds []string

builds keeps track of build contexts used to generate Builds.

	builds map[internal.BuildContext]bool

New indicates that the symbol is new as of the version where it is present. For example, if type Client was introduced in v1.0.0 and Client.Timeout was introduced in v1.1.0, New will be false for Client and true for Client.Timeout if this Symbol corresponds to v1.1.0.

	New bool
}

func (s *Symbol) addBuilds(builds ...internal.BuildContext) {
	if s.builds == nil {
		s.builds = map[internal.BuildContext]bool{}
	}
	for _, b := range builds {
		s.builds[b] = true
	}
}

symbolsForVersions returns an array of symbols for use in the VersionSummary of the specified version.

func symbolsForVersion(pkgURLPath string, symbolsAtVersion map[string]map[internal.SymbolMeta]*internal.SymbolBuildContexts) [][]*Symbol {
	nameToMetaToSymbol := map[string]map[internal.SymbolMeta]*Symbol{}
	children := map[internal.SymbolMeta]*internal.SymbolBuildContexts{}
	for _, smToUs := range symbolsAtVersion {
		for sm, us := range smToUs {

For the children, keep track of them for later.

				children[sm] = us
				continue
			}

			metaToSym, ok := nameToMetaToSymbol[sm.Name]
			if !ok {
				metaToSym = map[internal.SymbolMeta]*Symbol{}
				nameToMetaToSymbol[sm.Name] = metaToSym
			}
			s, ok := metaToSym[sm]
			if !ok {
				s = &Symbol{
					Name:     sm.Name,
					Synopsis: sm.Synopsis,
					Section:  sm.Section,
					Kind:     sm.Kind,
					Link:     symbolLink(pkgURLPath, sm.Name, us.BuildContexts()),
					New:      true,
				}
				nameToMetaToSymbol[s.Name][sm] = s
			}
			s.addBuilds(us.BuildContexts()...)
		}
	}

For each child symbol, 1 of 3 things can occur: Option 1: If no parent exists for this child symbol, make one and add the parent to the map. Option 2: A parent exists and does not support the build context of the child. This occurs when the parent type is introduced for another build context, but was introduced at the previous version for the current child. Create a new parent for this child. Option 3: A parent exists and does support the build context of the child. Add the child to the parent.

		cs := &Symbol{
			Name:     cm.Name,
			Synopsis: cm.Synopsis,
			Section:  cm.Section,
			Kind:     cm.Kind,
			Link:     symbolLink(pkgURLPath, cm.Name, cus.BuildContexts()),
			New:      true,
		}

		ps := findParent(cm.ParentName, cus, nameToMetaToSymbol)

Option 3: found a relevant parent.

			ps.Children = append(ps.Children, cs)
			continue
		}

Option 1 and 2: We did not find a relevant parent, so create one. Since this parent is not introduced at this version, create a distinct type for each group of symbols. To do so, we make up a synopsis for the SymbolMeta below, since it is only used as a key in nameToMetaToSymbol. Example case: http://pkg.go.dev/internal/poll?tab=versions for go1.10 should show: type FD -- windows/amd64 FD.ReadMsg FD.WriteMsg type FD -- darwin/amd64, linux/amd64 FD.SetBlocking FD.WriteOnce

		ps = createParent(cm.ParentName, pkgURLPath, cus.BuildContexts()...)
		pm := internal.SymbolMeta{
			Name:       ps.Name,
			ParentName: ps.Name,
			Synopsis:   fmt.Sprintf("type %s (%v)", ps.Name, cus.BuildContexts()),
			Section:    ps.Section,
			Kind:       ps.Kind,
		}
		ps.Children = append(ps.Children, cs)
		if _, ok := nameToMetaToSymbol[pm.Name]; !ok {
			nameToMetaToSymbol[pm.Name] = map[internal.SymbolMeta]*Symbol{}
		}
		nameToMetaToSymbol[pm.Name][pm] = ps
	}

	var symbols []*Symbol
	for _, mts := range nameToMetaToSymbol {
		for _, s := range mts {
			if len(s.builds) != len(internal.BuildContexts) {
				for b := range s.builds {
					s.Builds = append(s.Builds, fmt.Sprintf("%s/%s", b.GOOS, b.GOARCH))
				}
				sort.Strings(s.Builds)
			}
			symbols = append(symbols, s)
		}
	}
	return sortSymbols(symbols)
}

func findParent(parentName string, cus *internal.SymbolBuildContexts,
	nameToMetaToSymbol map[string]map[internal.SymbolMeta]*Symbol) *Symbol {
	parents, ok := nameToMetaToSymbol[parentName]
	if !ok {
		return nil
	}
	for _, ps := range parents {
		for build := range ps.builds {
			if cus.SupportsBuild(build) {
				return ps
			}
		}
	}
	return nil
}

func symbolLink(pkgURLPath, name string, builds []internal.BuildContext) string {
	if len(builds) == len(internal.BuildContexts) {
		return fmt.Sprintf("%s#%s", pkgURLPath, name)
	}

When a symbol is introduced for a specific GOOS/GOARCH at a version, linking to an unspecified GOOS/GOARCH page might not take the user to the symbol. Instead, link to one of the supported build contexts.

	return fmt.Sprintf("%s?GOOS=%s#%s", pkgURLPath, builds[0].GOOS, name)
}

createParent creates a parent symbol for the provided unit symbol. This is used when us is a child of a symbol that may have been introduced at a different version. The symbol created will have New set to false, since this function is only used when a parent symbol is not found for the unit symbol, which means it was not introduced at the same version.

func createParent(parentName, pkgURLPath string, builds ...internal.BuildContext) *Symbol {
	s := &Symbol{
		Name:     parentName,
		Synopsis: fmt.Sprintf("type %s", parentName),
		Section:  internal.SymbolSectionTypes,
		Kind:     internal.SymbolKindType,
		Link:     symbolLink(pkgURLPath, parentName, builds),
	}
	s.addBuilds(builds...)
	return s
}

sortSymbols returns an array of symbols in order of (1) Constants (2) Variables (3) Functions and (4) Types. Within each section, symbols are sorted alphabetically by name. In the types sections, aside from interfaces, child symbols are sorted in order of (1) Fields (2) Constants (3) Variables (4) Functions and (5) Methods. For interfaces, child symbols are sorted in order of (1) Methods (2) Constants (3) Variables and (4) Functions.

func sortSymbols(symbols []*Symbol) [][]*Symbol {
	sm := map[internal.SymbolSection][]*Symbol{}
	for _, parent := range symbols {
		sm[parent.Section] = append(sm[parent.Section], parent)
		cm := map[internal.SymbolKind][]*Symbol{}
		parent.Synopsis = strings.TrimSuffix(parent.Synopsis, "{ ... }")
		for _, c := range parent.Children {
			cm[c.Kind] = append(cm[c.Kind], c)
		}
		for _, syms := range cm {
			sortSymbolsGroup(syms)
		}
		symbols := append(append(append(
			cm[internal.SymbolKindField],
			cm[internal.SymbolKindConstant]...),
			cm[internal.SymbolKindVariable]...),
			cm[internal.SymbolKindFunction]...)
		if strings.Contains(parent.Synopsis, "interface") {
			parent.Children = append(cm[internal.SymbolKindMethod], symbols...)
		} else {
			parent.Children = append(symbols, cm[internal.SymbolKindMethod]...)
		}
	}
	for _, syms := range sm {
		sortSymbolsGroup(syms)
	}

	var out [][]*Symbol
	for _, section := range []internal.SymbolSection{
		internal.SymbolSectionConstants,
		internal.SymbolSectionVariables,
		internal.SymbolSectionFunctions,
		internal.SymbolSectionTypes} {
		if sm[section] != nil {
			out = append(out, sm[section])
		}
	}
	return out
}

func sortSymbolsGroup(syms []*Symbol) {
	sort.Slice(syms, func(i, j int) bool {
		s1 := syms[i]
		s2 := syms[j]
		if s1.Synopsis != s2.Synopsis {
			return s1.Synopsis < s2.Synopsis
		}
		return compareStringSlices(s1.Builds, s2.Builds) < 0
	})
}

func compareStringSlices(ss1, ss2 []string) int {
	for i, s1 := range ss1 {
		if i >= len(ss2) { // first slice is longer, so greater
			return 1
		}
		if c := strings.Compare(s1, ss2[i]); c != 0 {
			return c
		}
	}
	if len(ss1) == len(ss2) {
		return 0

first slice is shorter

	return -1
}

ParseVersionsDetails returns a map of versionToNameToUnitSymbol based on data from the proovided VersionDetails.

func ParseVersionsDetails(vd VersionsDetails) (_ *internal.SymbolHistory, err error) {
	sh := internal.NewSymbolHistory()
	for _, vl := range vd.ThisModule {
		for _, vs := range vl.Versions {
			v := vs.Version
			if vd.ThisModule[0].ModulePath == stdlib.ModulePath {
				v = stdlib.VersionForTag(v)
			}
			for _, syms := range vs.Symbols {
				for _, s := range syms {
					if s.New {
						addSymbol(s, v, sh, s.Builds)
					}
					for _, c := range s.Children {
						addSymbol(c, v, sh, s.Builds)
					}
				}
			}
		}
	}
	return sh, nil
}

func addSymbol(s *Symbol, v string, sh *internal.SymbolHistory, builds []string) {
	sm := internal.SymbolMeta{
		Name: s.Name,
	}
	if len(builds) == 0 {
		sh.AddSymbol(sm, v, internal.BuildContextAll)
		return
	}
	for _, b := range builds {
		parts := strings.SplitN(b, "/", 2)
		var build internal.BuildContext
		switch parts[0] {
		case "linux":
			build = internal.BuildContextLinux
		case "darwin":
			build = internal.BuildContextDarwin
		case "windows":
			build = internal.BuildContextWindows
		case "js":
			build = internal.BuildContextJS
		}
		sh.AddSymbol(sm, v, build)
	}