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module.go
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module.go
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package require
import (
"errors"
"io"
"io/fs"
"os"
"path"
"path/filepath"
"runtime"
"sync"
"syscall"
"text/template"
js "github.com/dop251/goja"
"github.com/dop251/goja/parser"
)
type ModuleLoader func(*js.Runtime, *js.Object)
// SourceLoader represents a function that returns a file data at a given path.
// The function should return ModuleFileDoesNotExistError if the file either doesn't exist or is a directory.
// This error will be ignored by the resolver and the search will continue. Any other errors will be propagated.
type SourceLoader func(path string) ([]byte, error)
var (
InvalidModuleError = errors.New("Invalid module")
IllegalModuleNameError = errors.New("Illegal module name")
NoSuchBuiltInModuleError = errors.New("No such built-in module")
ModuleFileDoesNotExistError = errors.New("module file does not exist")
)
var native, builtin map[string]ModuleLoader
// Registry contains a cache of compiled modules which can be used by multiple Runtimes
type Registry struct {
sync.Mutex
native map[string]ModuleLoader
compiled map[string]*js.Program
srcLoader SourceLoader
globalFolders []string
}
type RequireModule struct {
r *Registry
runtime *js.Runtime
modules map[string]*js.Object
nodeModules map[string]*js.Object
}
func NewRegistry(opts ...Option) *Registry {
r := &Registry{}
for _, opt := range opts {
opt(r)
}
return r
}
func NewRegistryWithLoader(srcLoader SourceLoader) *Registry {
return NewRegistry(WithLoader(srcLoader))
}
type Option func(*Registry)
// WithLoader sets a function which will be called by the require() function in order to get a source code for a
// module at the given path. The same function will be used to get external source maps.
// Note, this only affects the modules loaded by the require() function. If you need to use it as a source map
// loader for code parsed in a different way (such as runtime.RunString() or eval()), use (*Runtime).SetParserOptions()
func WithLoader(srcLoader SourceLoader) Option {
return func(r *Registry) {
r.srcLoader = srcLoader
}
}
// WithGlobalFolders appends the given paths to the registry's list of
// global folders to search if the requested module is not found
// elsewhere. By default, a registry's global folders list is empty.
// In the reference Node.js implementation, the default global folders
// list is $NODE_PATH, $HOME/.node_modules, $HOME/.node_libraries and
// $PREFIX/lib/node, see
// https://nodejs.org/api/modules.html#modules_loading_from_the_global_folders.
func WithGlobalFolders(globalFolders ...string) Option {
return func(r *Registry) {
r.globalFolders = globalFolders
}
}
// Enable adds the require() function to the specified runtime.
func (r *Registry) Enable(runtime *js.Runtime) *RequireModule {
rrt := &RequireModule{
r: r,
runtime: runtime,
modules: make(map[string]*js.Object),
nodeModules: make(map[string]*js.Object),
}
runtime.Set("require", rrt.require)
return rrt
}
func (r *Registry) RegisterNativeModule(name string, loader ModuleLoader) {
r.Lock()
defer r.Unlock()
if r.native == nil {
r.native = make(map[string]ModuleLoader)
}
name = filepathClean(name)
r.native[name] = loader
}
// DefaultSourceLoader is used if none was set (see WithLoader()). It simply loads files from the host's filesystem.
func DefaultSourceLoader(filename string) ([]byte, error) {
fp := filepath.FromSlash(filename)
f, err := os.Open(fp)
if err != nil {
if errors.Is(err, fs.ErrNotExist) {
err = ModuleFileDoesNotExistError
} else if runtime.GOOS == "windows" {
if errors.Is(err, syscall.Errno(0x7b)) { // ERROR_INVALID_NAME, The filename, directory name, or volume label syntax is incorrect.
err = ModuleFileDoesNotExistError
}
}
return nil, err
}
defer f.Close()
// On some systems (e.g. plan9 and FreeBSD) it is possible to use the standard read() call on directories
// which means we cannot rely on read() returning an error, we have to do stat() instead.
if fi, err := f.Stat(); err == nil {
if fi.IsDir() {
return nil, ModuleFileDoesNotExistError
}
} else {
return nil, err
}
return io.ReadAll(f)
}
func (r *Registry) getSource(p string) ([]byte, error) {
srcLoader := r.srcLoader
if srcLoader == nil {
srcLoader = DefaultSourceLoader
}
return srcLoader(p)
}
func (r *Registry) getCompiledSource(p string) (*js.Program, error) {
r.Lock()
defer r.Unlock()
prg := r.compiled[p]
if prg == nil {
buf, err := r.getSource(p)
if err != nil {
return nil, err
}
s := string(buf)
if path.Ext(p) == ".json" {
s = "module.exports = JSON.parse('" + template.JSEscapeString(s) + "')"
}
source := "(function(exports, require, module) {" + s + "\n})"
parsed, err := js.Parse(p, source, parser.WithSourceMapLoader(r.srcLoader))
if err != nil {
return nil, err
}
prg, err = js.CompileAST(parsed, false)
if err == nil {
if r.compiled == nil {
r.compiled = make(map[string]*js.Program)
}
r.compiled[p] = prg
}
return prg, err
}
return prg, nil
}
func (r *RequireModule) require(call js.FunctionCall) js.Value {
ret, err := r.Require(call.Argument(0).String())
if err != nil {
if _, ok := err.(*js.Exception); !ok {
panic(r.runtime.NewGoError(err))
}
panic(err)
}
return ret
}
func filepathClean(p string) string {
return path.Clean(p)
}
// Require can be used to import modules from Go source (similar to JS require() function).
func (r *RequireModule) Require(p string) (ret js.Value, err error) {
module, err := r.resolve(p)
if err != nil {
return
}
ret = module.Get("exports")
return
}
func Require(runtime *js.Runtime, name string) js.Value {
if r, ok := js.AssertFunction(runtime.Get("require")); ok {
mod, err := r(js.Undefined(), runtime.ToValue(name))
if err != nil {
panic(err)
}
return mod
}
panic(runtime.NewTypeError("Please enable require for this runtime using new(require.Registry).Enable(runtime)"))
}
// RegisterNativeModule registers a module that isn't loaded through a SourceLoader, but rather through
// a provided ModuleLoader. Typically, this will be a module implemented in Go (although theoretically
// it can be anything, depending on the ModuleLoader implementation).
// Such modules take precedence over modules loaded through a SourceLoader, i.e. if a module name resolves as
// native, the native module is loaded, and the SourceLoader is not consulted.
// The binding is global and affects all instances of Registry.
// It should be called from a package init() function as it may not be used concurrently with require() calls.
// For registry-specific bindings see Registry.RegisterNativeModule.
func RegisterNativeModule(name string, loader ModuleLoader) {
if native == nil {
native = make(map[string]ModuleLoader)
}
name = filepathClean(name)
native[name] = loader
}
// RegisterCoreModule registers a nodejs core module. If the name does not start with "node:", the module
// will also be loadable as "node:<name>". Hence, for "builtin" modules (such as buffer, console, etc.)
// the name should not include the "node:" prefix, but for prefix-only core modules (such as "node:test")
// it should include the prefix.
func RegisterCoreModule(name string, loader ModuleLoader) {
if builtin == nil {
builtin = make(map[string]ModuleLoader)
}
name = filepathClean(name)
builtin[name] = loader
}