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visitor.go
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visitor.go
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// Copyright © 2023 The Gomon Project.
package main
import (
"fmt"
"go/ast"
"go/build"
"go/build/constraint"
"go/types"
"os"
"path"
"strings"
"github.com/zosmac/gocore"
)
type (
// visitor employed by the AST walk of the parse function.
visitor struct {
pkg *ast.Package
}
// table maps tree nodes to their data.
table = gocore.Table[string, any]
// tree organizes information types parsed from packages.
tree = gocore.Tree[string, string, any]
// TREE is the enumberation type for information types parsed from packages.
TREE int
)
const (
IMPORTS TREE = iota
INTERFACES
TYPES
VALUES
FUNCTIONS
DEFINES
REFERENCES
IMPLEMENTS
TREES
)
var (
// dirstd is the location of the Go standard packages source.
dirstd = path.Join(build.Default.GOROOT, "src")
// dirimps is the location of the source for imported Go packages.
dirimps = path.Join(build.Default.GOPATH, "pkg", "mod")
// gomod, dirmod are the import path and directory location of the module.
gomod, dirmod string
// aliases map selection names used in a file to the imported package names.
aliases = map[string]string{} // alias:package
// trees creates a slice that anchors all of the information types parsed from packages.
trees = func() []tree {
ts := make([]tree, TREES)
for i := range ts {
ts[i] = tree{}
}
return ts
}()
// imps tree reports all imported packages.
imps = trees[IMPORTS]
// ifcs tree reports all interfaces.
ifcs = trees[INTERFACES]
// typs tree reports all exported types.
typs = trees[TYPES]
// vals tree reports all exported values.
vals = trees[VALUES]
// fncs tree reports all exported functions.
fncs = trees[FUNCTIONS]
// defs tree reports where types, values, and functions are defined.
defs = trees[DEFINES]
// refs tree reports where types, values, and functions are referenced.
refs = trees[REFERENCES]
// sets tree reports interfaces with types whose method sets comply.
sets = trees[IMPLEMENTS]
)
// path determines the location of a node.
func (v visitor) path(node ast.Node) string {
pth := fileSet.File(node.Pos()).Name()
if b, a, ok := strings.Cut(pth, "@"); ok { // strip version
if _, a, ok := strings.Cut(a, "/"); ok { // reassemble path
pth = path.Join(b, a)
} else {
pth = b
}
}
if ext := path.Ext(pth); ext == ".go" {
pth = path.Dir(pth)
}
return pth
}
// Visit evaluates each node of the AST.
func (v visitor) Visit(node ast.Node) ast.Visitor {
if node == nil {
return nil
}
switch node := node.(type) {
// STATEMENTS
case *ast.AssignStmt,
*ast.BadStmt,
*ast.BlockStmt,
*ast.BranchStmt,
*ast.CaseClause,
*ast.CommClause,
*ast.DeclStmt,
*ast.DeferStmt,
*ast.EmptyStmt,
*ast.ExprStmt,
*ast.ForStmt,
*ast.GoStmt,
*ast.IfStmt,
*ast.IncDecStmt,
*ast.LabeledStmt,
*ast.RangeStmt,
*ast.ReturnStmt,
*ast.SelectStmt,
*ast.SendStmt,
*ast.SwitchStmt,
*ast.TypeSwitchStmt:
case ast.Stmt: // put this last after all the explicit statement types
panic(fmt.Errorf("unexpected stmt type %T %[1]s", node))
// IDENTITY EXPRESSION
case *ast.Ident:
addRef(v, v.pkg.Name, node)
// LITERAL EXPRESSIONS
case *ast.BasicLit,
*ast.CompositeLit,
*ast.Ellipsis,
*ast.FuncLit:
// TYPE EXPRESSIONS
case *ast.ArrayType,
*ast.ChanType,
*ast.FuncType,
*ast.InterfaceType,
*ast.MapType,
*ast.StructType:
// COMPLEX EXPRESSIONS
case *ast.BinaryExpr,
*ast.CallExpr,
*ast.IndexExpr,
*ast.IndexListExpr,
*ast.KeyValueExpr,
*ast.ParenExpr,
*ast.SliceExpr,
*ast.StarExpr,
*ast.TypeAssertExpr,
*ast.UnaryExpr:
case *ast.SelectorExpr:
addRef(v, types.ExprString(node.X), node.Sel)
case ast.Expr: // put this last after all the explicit expression types
panic(fmt.Errorf("unexpected expr type %T %[1]s", node))
// SPECS
case *ast.ImportSpec:
for skip := range skipdirs {
if strings.Contains(node.Path.Value, skip) {
return nil
}
}
addImp(node)
case *ast.TypeSpec:
addTyp(v, node)
case *ast.ValueSpec:
addVal(v, node)
case ast.Spec:
panic(fmt.Errorf("unexpected spec type %T %[1]s", node))
// NODES
case *ast.Package:
for pth, file := range node.Files {
if !gobuild(pth, file) {
delete(node.Files, pth)
}
}
case *ast.File:
aliases = map[string]string{}
case *ast.FuncDecl:
addFnc(v, node)
case *ast.CommentGroup,
*ast.Comment,
*ast.FieldList,
*ast.Field,
*ast.GenDecl:
default:
panic(fmt.Errorf("unexpected node type %T %[1]s", node))
}
return v
}
// gobuild evaluates a file's build constraints to determine whether to parse it.
func gobuild(pth string, file *ast.File) bool {
for _, group := range file.Comments { // look for go:build
if group.Pos() > file.Package {
break // skip comments after the package statement
}
for _, comment := range group.List {
if constraint.IsGoBuild(comment.Text) {
expr, _ := constraint.Parse(comment.Text)
return expr.Eval(func(tag string) bool {
return tag == build.Default.GOOS
})
}
}
}
if pth == "" {
return true
}
// create build constraint from file name
if s := strings.Join( // build constraint expression
strings.Split(
strings.TrimSuffix( // remove file extension
path.Base(pth),
path.Ext(pth),
),
"_")[1:], // separate name from build constraints
" && ",
); len(s) == 0 { // no constraints in file name
return true
} else { // evaluate constraints in file name
expr, _ := constraint.Parse("//go:build " + s)
return expr.Eval(func(tag string) bool {
return tag == build.Default.GOOS
})
}
}
// addImp adds an import to the list of imports.
func addImp(node *ast.ImportSpec) {
pth := strings.Trim(node.Path.Value, "\"")
pkg, _, _ := strings.Cut(path.Base(pth), ".") // if package name has ".", strip following (i.e. version)
if pth == "C" { // skip "C" package
return
}
// convert import path to local directory path
var abs string
if rel, err := gocore.Subdir(dirmod, pth); err == nil { // package in current module
abs = path.Join(dirmod, rel)
} else if _, err := os.Stat(path.Join(dirstd, pth)); err == nil { // std package
abs = path.Join(dirstd, pth)
} else {
abs = path.Join(dirimps, pth) // package from imports
}
var alias string
if node.Name == nil {
alias = pkg
} else {
alias = node.Name.Name
}
aliases[alias] = pkg
imps.Add(pkg, abs)
}
// addTyp adds a type to the typs or ifcs list.
func addTyp(v visitor, node *ast.TypeSpec) {
if !ast.IsExported(node.Name.Name) {
return
}
addDef(v, node.Name)
name := v.pkg.Name + "." + node.Name.Name
switch expr := node.Type.(type) {
case *ast.InterfaceType:
addIfc(v, name, expr)
case *ast.StructType:
addStr(name, expr)
case *ast.CompositeLit:
lit := types.ExprString(expr.Type)
for _, elt := range expr.Elts {
typs.Add(name, lit, types.ExprString(elt))
}
default:
typs.Add(name, types.ExprString(expr))
}
}
// addIfc adds an interface and its methods to the list of interfaces.
func addIfc(v visitor, name string, node *ast.InterfaceType) {
for _, mth := range node.Methods.List {
if len(mth.Names) == 0 {
// embedded interface type
dt := types.ExprString(mth.Type)
if !strings.Contains(dt, ".") && ast.IsExported(dt) {
dt = v.pkg.Name + "." + dt // interface is in this package
}
ifcs.Add(name, dt)
} else {
for _, id := range mth.Names {
ifcs.Add(name, id.Name+signature(mth.Type.(*ast.FuncType)))
}
}
}
}
// addStr adds a structure declaration to the list of types.
func addStr(name string, node *ast.StructType) {
for _, fld := range node.Fields.List {
names := make([]string, len(fld.Names))
for i, id := range fld.Names {
names[i] = id.Name
}
line := strings.Join(names, ", ")
if fnc, ok := fld.Type.(*ast.FuncType); ok {
line += signature(fnc)
} else {
if len(line) > 0 {
line += " "
}
expr := fld.Type
if s, ok := expr.(*ast.StarExpr); ok {
expr = s.X
}
line += types.ExprString(expr)
}
if ast.IsExported(line) {
typs.Add(name, line)
}
}
}
// addVal adds a value to the list of values.
func addVal(v visitor, node *ast.ValueSpec) {
for _, id := range node.Names {
if !ast.IsExported(id.Name) {
continue
}
addDef(v, id)
name := v.pkg.Name + "." + id.Name
for _, val := range node.Values {
vals.Add(name, types.ExprString(val))
}
}
}
// addFnc adds function to the functions list or method to a type in the types list
func addFnc(v visitor, node *ast.FuncDecl) {
if !ast.IsExported(node.Name.Name) {
return
}
addDef(v, node.Name)
if node.Recv == nil || len(node.Recv.List) == 0 {
fncs.Add(v.pkg.Name + "." + node.Name.Name + signature(node.Type))
} else {
expr := node.Recv.List[0].Type
if s, ok := expr.(*ast.StarExpr); ok {
expr = s.X
}
name := types.ExprString(expr) // methods key off receiver type
if !ast.IsExported(name) {
return
}
typs.Add(v.pkg.Name+"."+name, node.Name.Name+signature(node.Type))
}
}
// addDef adds the location where an identifier is defined.
func addDef(v visitor, id *ast.Ident) {
defs.Add(v.pkg.Name+"."+id.Name, v.path(id))
}
// addRef adds the location where an identifier is referenced.
func addRef(v visitor, qualifier string, id *ast.Ident) {
if !ast.IsExported(id.Name) {
return
}
if pkg := aliases[qualifier]; pkg != "" {
refs.Add(pkg+"."+id.Name, v.path(id))
}
}
// signature formats the parameter and result types of a function or method.
func signature(node *ast.FuncType) string {
parms := "(" + typelist(node.Params) + ")"
rslts := typelist(node.Results)
if rslts != "" {
parms += " "
}
if strings.Contains(rslts, ",") {
rslts = " (" + rslts + ")"
}
return parms + rslts
}
// typelist reports the types of a list of fields.
func typelist(flds *ast.FieldList) string {
if flds == nil {
return ""
}
var typs []string
for _, fld := range flds.List {
typ := types.ExprString(fld.Type)
typs = append(typs, typ)
for i := 1; i < len(fld.Names); i++ {
typs = append(typs, typ)
}
}
return strings.Join(typs, ", ")
}