/
eval.go
428 lines (369 loc) · 11.3 KB
/
eval.go
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// Package eval handles evaluation of parsed Elvish code and provides runtime
// facilities.
package eval
import (
"context"
"fmt"
"io"
"os"
"strconv"
"sync"
"src.elv.sh/pkg/env"
"src.elv.sh/pkg/eval/vals"
"src.elv.sh/pkg/eval/vars"
"src.elv.sh/pkg/logutil"
"src.elv.sh/pkg/parse"
)
var logger = logutil.GetLogger("[eval] ")
const (
// FnSuffix is the suffix for the variable names of functions. Defining a
// function "foo" is equivalent to setting a variable named "foo~", and vice
// versa.
FnSuffix = "~"
// NsSuffix is the suffix for the variable names of namespaces. Defining a
// namespace foo is equivalent to setting a variable named "foo:", and vice
// versa.
NsSuffix = ":"
)
const (
defaultValuePrefix = "▶ "
defaultNotifyBgJobSuccess = true
)
// Evaler provides methods for evaluating code, and maintains state that is
// persisted between evaluation of different pieces of code. An Evaler is safe
// to use concurrently.
type Evaler struct {
// The following fields must only be set before the Evaler is used to
// evaluate any code; mutating them afterwards may cause race conditions.
// Command-line arguments, exposed as $args.
Args vals.List
// Hooks to run before exit or exec.
PreExitHooks []func()
// Chdir hooks, exposed indirectly as $before-chdir and $after-chdir.
BeforeChdir, AfterChdir []func(string)
// Directories to search libraries.
LibDirs []string
// Source code of internal bundled modules indexed by use specs.
BundledModules map[string]string
// Callback to notify the success or failure of background jobs. Must not be
// mutated once the Evaler is used to evaluate any code.
BgJobNotify func(string)
// Path to the rc file, and path to the rc file actually evaluated. These
// are not used by the Evaler itself right now; they are here so that they
// can be exposed to the runtime: module.
RcPath, EffectiveRcPath string
mu sync.RWMutex
// Mutations to fields below must be guarded by mutex.
//
// Note that this is *not* a GIL; most state mutations when executing Elvish
// code is localized and do not need to hold this mutex.
//
// TODO: Actually guard all mutations by this mutex.
global, builtin *Ns
deprecations deprecationRegistry
// Internal modules are indexed by use specs. External modules are indexed by
// absolute paths.
modules map[string]*Ns
// Various states and configs exposed to Elvish code.
//
// The prefix to prepend to value outputs when writing them to terminal,
// exposed as $value-out-prefix.
valuePrefix string
// Whether to notify the success of background jobs, exposed as
// $notify-bg-job-sucess.
notifyBgJobSuccess bool
// The current number of background jobs, exposed as $num-bg-jobs.
numBgJobs int
}
// NewEvaler creates a new Evaler.
func NewEvaler() *Evaler {
builtin := builtinNs.Ns()
newListVar := func(l vals.List) vars.PtrVar { return vars.FromPtr(&l) }
beforeExitHookElvish := newListVar(vals.EmptyList)
beforeChdirElvish := newListVar(vals.EmptyList)
afterChdirElvish := newListVar(vals.EmptyList)
ev := &Evaler{
global: new(Ns),
builtin: builtin,
deprecations: newDeprecationRegistry(),
modules: make(map[string]*Ns),
BundledModules: make(map[string]string),
valuePrefix: defaultValuePrefix,
notifyBgJobSuccess: defaultNotifyBgJobSuccess,
numBgJobs: 0,
Args: vals.EmptyList,
}
ev.PreExitHooks = []func(){func() {
CallHook(ev, nil, "before-exit", beforeExitHookElvish.Get().(vals.List))
}}
ev.BeforeChdir = []func(string){func(path string) {
CallHook(ev, nil, "before-chdir", beforeChdirElvish.Get().(vals.List), path)
}}
ev.AfterChdir = []func(string){func(path string) {
CallHook(ev, nil, "after-chdir", afterChdirElvish.Get().(vals.List), path)
}}
ev.ExtendBuiltin(BuildNs().
AddVar("pwd", NewPwdVar(ev)).
AddVar("before-exit", beforeExitHookElvish).
AddVar("before-chdir", beforeChdirElvish).
AddVar("after-chdir", afterChdirElvish).
AddVar("value-out-indicator",
vars.FromPtrWithMutex(&ev.valuePrefix, &ev.mu)).
AddVar("notify-bg-job-success",
vars.FromPtrWithMutex(&ev.notifyBgJobSuccess, &ev.mu)).
AddVar("num-bg-jobs",
vars.FromGet(func() any { return strconv.Itoa(ev.getNumBgJobs()) })).
AddVar("args", vars.FromGet(func() any { return ev.Args })))
// Install the "builtin" module after extension is complete.
ev.modules["builtin"] = ev.builtin
return ev
}
// PreExit runs all pre-exit hooks.
func (ev *Evaler) PreExit() {
for _, hook := range ev.PreExitHooks {
hook()
}
}
// Access methods.
// Global returns the global Ns.
func (ev *Evaler) Global() *Ns {
ev.mu.RLock()
defer ev.mu.RUnlock()
return ev.global
}
// ExtendGlobal extends the global namespace with the given namespace.
func (ev *Evaler) ExtendGlobal(ns Nser) {
ev.mu.Lock()
defer ev.mu.Unlock()
ev.global = CombineNs(ev.global, ns.Ns())
}
// DeleteFromGlobal deletes names from the global namespace.
func (ev *Evaler) DeleteFromGlobal(names map[string]struct{}) {
ev.mu.Lock()
defer ev.mu.Unlock()
g := ev.global.clone()
for i := range g.infos {
if _, ok := names[g.infos[i].name]; ok {
g.infos[i].deleted = true
}
}
ev.global = g
}
// Builtin returns the builtin Ns.
func (ev *Evaler) Builtin() *Ns {
ev.mu.RLock()
defer ev.mu.RUnlock()
return ev.builtin
}
// ExtendBuiltin extends the builtin namespace with the given namespace.
func (ev *Evaler) ExtendBuiltin(ns Nser) {
ev.mu.Lock()
defer ev.mu.Unlock()
ev.builtin = CombineNs(ev.builtin, ns.Ns())
}
// ReplaceBuiltin replaces the builtin namespace. It should only be used in
// tests.
func (ev *Evaler) ReplaceBuiltin(ns *Ns) {
ev.mu.Lock()
defer ev.mu.Unlock()
ev.builtin = ns
}
func (ev *Evaler) registerDeprecation(d deprecation) bool {
ev.mu.Lock()
defer ev.mu.Unlock()
return ev.deprecations.register(d)
}
// AddModule add an internal module so that it can be used with "use $name" from
// script.
func (ev *Evaler) AddModule(name string, mod *Ns) {
ev.mu.Lock()
defer ev.mu.Unlock()
ev.modules[name] = mod
}
// ValuePrefix returns the prefix to prepend to value outputs when writing them
// to terminal.
func (ev *Evaler) ValuePrefix() string {
ev.mu.RLock()
defer ev.mu.RUnlock()
return ev.valuePrefix
}
func (ev *Evaler) getNotifyBgJobSuccess() bool {
ev.mu.RLock()
defer ev.mu.RUnlock()
return ev.notifyBgJobSuccess
}
func (ev *Evaler) getNumBgJobs() int {
ev.mu.RLock()
defer ev.mu.RUnlock()
return ev.numBgJobs
}
func (ev *Evaler) addNumBgJobs(delta int) {
ev.mu.Lock()
defer ev.mu.Unlock()
ev.numBgJobs += delta
}
// Chdir changes the current directory, and updates $E:PWD on success
//
// It runs the functions in beforeChdir immediately before changing the
// directory, and the functions in afterChdir immediately after (if chdir was
// successful). It returns nil as long as the directory changing part succeeds.
func (ev *Evaler) Chdir(path string) error {
for _, hook := range ev.BeforeChdir {
hook(path)
}
err := os.Chdir(path)
if err != nil {
return err
}
for _, hook := range ev.AfterChdir {
hook(path)
}
pwd, err := os.Getwd()
if err != nil {
logger.Println("getwd after cd:", err)
return nil
}
os.Setenv(env.PWD, pwd)
return nil
}
// EvalCfg keeps configuration for the (*Evaler).Eval method.
type EvalCfg struct {
// Context that can be used to cancel the evaluation.
Interrupts context.Context
// Ports to use in evaluation. The first 3 elements, if not specified
// (either being nil or Ports containing fewer than 3 elements),
// will be filled with DummyInputPort, DummyOutputPort and
// DummyOutputPort respectively.
Ports []*Port
// Whether the Eval method should try to put the Elvish in the foreground
// after the code is executed.
PutInFg bool
// If not nil, used the given global namespace, instead of Evaler's own.
Global *Ns
}
func (cfg *EvalCfg) fillDefaults() {
if len(cfg.Ports) < 3 {
cfg.Ports = append(cfg.Ports, make([]*Port, 3-len(cfg.Ports))...)
}
if cfg.Ports[0] == nil {
cfg.Ports[0] = DummyInputPort
}
if cfg.Ports[1] == nil {
cfg.Ports[1] = DummyOutputPort
}
if cfg.Ports[2] == nil {
cfg.Ports[2] = DummyOutputPort
}
}
// Eval evaluates a piece of source code with the given configuration. The
// returned error may be a parse error, compilation error or exception.
func (ev *Evaler) Eval(src parse.Source, cfg EvalCfg) error {
cfg.fillDefaults()
errFile := cfg.Ports[2].File
tree, err := parse.Parse(src, parse.Config{WarningWriter: errFile})
if err != nil {
return err
}
ev.mu.Lock()
b := ev.builtin
defaultGlobal := cfg.Global == nil
if defaultGlobal {
// If cfg.Global is nil, use the Evaler's default global, and also
// mutate the default global.
cfg.Global = ev.global
// Continue to hold the mutex; it will be released when ev.global gets
// mutated.
} else {
ev.mu.Unlock()
}
op, _, err := compile(b.static(), cfg.Global.static(), nil, tree, errFile)
if err != nil {
if defaultGlobal {
ev.mu.Unlock()
}
return err
}
fm, cleanup := ev.prepareFrame(src, cfg)
defer cleanup()
newLocal, exec := op.prepare(fm)
if defaultGlobal {
ev.global = newLocal
ev.mu.Unlock()
}
return exec()
}
// CallCfg keeps configuration for the (*Evaler).Call method.
type CallCfg struct {
// Arguments to pass to the function.
Args []any
// Options to pass to the function.
Opts map[string]any
// The name of the internal source that is calling the function.
From string
}
func (cfg *CallCfg) fillDefaults() {
if cfg.Opts == nil {
cfg.Opts = NoOpts
}
if cfg.From == "" {
cfg.From = "[internal]"
}
}
// Call calls a given function.
func (ev *Evaler) Call(f Callable, callCfg CallCfg, evalCfg EvalCfg) error {
callCfg.fillDefaults()
evalCfg.fillDefaults()
if evalCfg.Global == nil {
evalCfg.Global = ev.Global()
}
fm, cleanup := ev.prepareFrame(parse.Source{Name: callCfg.From}, evalCfg)
defer cleanup()
return f.Call(fm, callCfg.Args, callCfg.Opts)
}
func (ev *Evaler) prepareFrame(src parse.Source, cfg EvalCfg) (*Frame, func()) {
intCtx := cfg.Interrupts
if intCtx == nil {
intCtx = context.Background()
}
ports := fillDefaultDummyPorts(cfg.Ports)
fm := &Frame{ev, src, cfg.Global, new(Ns), nil, intCtx, ports, nil, false}
return fm, func() {
if cfg.PutInFg {
err := putSelfInFg()
if err != nil {
fmt.Fprintln(ports[2].File,
"failed to put myself in foreground:", err)
}
}
}
}
func fillDefaultDummyPorts(ports []*Port) []*Port {
growPorts(&ports, 3)
if ports[0] == nil {
ports[0] = DummyInputPort
}
if ports[1] == nil {
ports[1] = DummyOutputPort
}
if ports[2] == nil {
ports[2] = DummyOutputPort
}
return ports
}
// Check checks the given source code for any parse error, autofixes, and
// compilation error. It always tries to compile the code even if there is a
// parse error. If w is not nil, deprecation messages are written to it.
func (ev *Evaler) Check(src parse.Source, w io.Writer) (error, []string, error) {
tree, parseErr := parse.Parse(src, parse.Config{WarningWriter: w})
autofixes, compileErr := ev.CheckTree(tree, w)
return parseErr, autofixes, compileErr
}
// CheckTree checks the given parsed source tree for autofixes and compilation
// errors. If w is not nil, deprecation messages are written to it.
func (ev *Evaler) CheckTree(tree parse.Tree, w io.Writer) ([]string, error) {
ev.mu.RLock()
b, g, m := ev.builtin, ev.global, ev.modules
ev.mu.RUnlock()
_, autofixes, compileErr := compile(b.static(), g.static(), mapKeys(m), tree, w)
return autofixes, compileErr
}