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evaluate.go
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evaluate.go
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package typescript
import (
"context"
"fmt"
"io"
"io/ioutil"
"strings"
"github.com/clarkmcc/go-typescript/packages"
_ "github.com/clarkmcc/go-typescript/versions/v4.7.2"
"github.com/dop251/goja"
)
type EvaluateOptionFunc func(cfg *EvaluateConfig)
type EvaluateConfig struct {
// EvaluateBefore are sequentially evaluated in the Javascript runtime before evaluating the provided script.
EvaluateBefore []io.Reader
// ScriptHooks are called after transpiling (if applicable) with the script that will be evaluated immediately
// before evaluation. If an error is returned from any of these functions, the evaluation process is aborted.
// The script hook can make modifications and return them to the script if necessary.
ScriptHooks []func(string) (string, error)
// ScriptPreTranspileHooks are called before transpiling (if applicable) with the script that will be evaluated
ScriptPreTranspileHooks []func(string) (string, error)
// Transpile indicates whether the script should be transpiled before its evaluated in the runtime.
Transpile bool
// TranspileOptions are options passed directly to the transpiler if applicable
TranspileOptions []TranspileOptionFunc
// Runtime is the goja runtime used for script execution. If not specified, it defaults to an empty runtime
Runtime *goja.Runtime
}
// ApplyDefaults applies defaults to the configuration and is called automatically before the config is used
func (cfg *EvaluateConfig) ApplyDefaults() {
if cfg.Runtime == nil {
cfg.Runtime = goja.New()
}
}
func (cfg *EvaluateConfig) HasEvaluateBefore() bool {
return len(cfg.EvaluateBefore) > 0
}
// WithEvaluationRuntime allows callers to use their own runtimes with the evaluator.
func WithEvaluationRuntime(runtime *goja.Runtime) EvaluateOptionFunc {
return func(cfg *EvaluateConfig) {
cfg.Runtime = runtime
}
}
// WithEvaluateBefore adds scripts that should be evaluated before evaluating the provided script. Each provided script
// is evaluated in the order that it's provided.
func WithEvaluateBefore(sources ...io.Reader) EvaluateOptionFunc {
return func(cfg *EvaluateConfig) {
cfg.EvaluateBefore = append(cfg.EvaluateBefore, sources...)
}
}
// WithAlmondModuleLoader adds the almond module loader to the list of scripts that should be evaluated first
func WithAlmondModuleLoader() EvaluateOptionFunc {
return WithEvaluateBefore(strings.NewReader(packages.Almond))
}
// WithTranspile indicates whether the provided script should be transpiled before it is evaluated. This does not
// mean that all the evaluate before's will be transpiled as well, only the src provided to EvaluateCtx will be transpiled
func WithTranspile() EvaluateOptionFunc {
return func(cfg *EvaluateConfig) {
cfg.Transpile = true
}
}
// WithTranspileOptions adds options to be passed to the transpiler if the transpiler is applicable
func WithTranspileOptions(opts ...TranspileOptionFunc) EvaluateOptionFunc {
return func(cfg *EvaluateConfig) {
cfg.TranspileOptions = append(cfg.TranspileOptions, opts...)
}
}
// WithScriptHook adds a script hook that should be evaluated immediately before the actual script evaluation
func WithScriptHook(hook func(script string) (string, error)) EvaluateOptionFunc {
return func(cfg *EvaluateConfig) {
cfg.ScriptHooks = append(cfg.ScriptHooks, hook)
}
}
// WithScriptPreTranspileHook adds a script hook that should be evaluated immediately before transpiling the script
func WithScriptPreTranspileHook(hook func(script string) (string, error)) EvaluateOptionFunc {
return func(cfg *EvaluateConfig) {
cfg.ScriptPreTranspileHooks = append(cfg.ScriptPreTranspileHooks, hook)
}
}
// Evaluate calls EvaluateCtx using the default background context
func Evaluate(src io.Reader, opts ...EvaluateOptionFunc) (goja.Value, error) {
return EvaluateCtx(context.Background(), src, opts...)
}
// EvaluateCtx evaluates the provided src using the specified options and returns the goja value result or an error.
func EvaluateCtx(ctx context.Context, src io.Reader, opts ...EvaluateOptionFunc) (result goja.Value, err error) {
cfg := &EvaluateConfig{}
cfg.ApplyDefaults()
for _, fn := range opts {
fn(cfg)
}
done := startInterruptable(ctx, cfg.Runtime)
defer close(done)
if cfg.HasEvaluateBefore() {
for _, s := range cfg.EvaluateBefore {
b, err := ioutil.ReadAll(s)
if err != nil {
return nil, fmt.Errorf("reading evaluate befores: %w", err)
}
_, err = cfg.Runtime.RunString(string(b))
if err != nil {
return nil, fmt.Errorf("evaluating evaluate befores: %w", err)
}
}
}
b, err := ioutil.ReadAll(src)
if err != nil {
return nil, fmt.Errorf("reading src: %w", err)
}
script := string(b)
if cfg.Transpile {
// This is needed in case the script being transpiled imports other modules. Check if it already exists in case
// the caller has their own implementation and use of the global exports object.
if cfg.Runtime.Get("exports") == nil {
err = cfg.Runtime.Set("exports", cfg.Runtime.NewObject())
if err != nil {
return nil, fmt.Errorf("setting exports object: %w", err)
}
}
opts := []TranspileOptionFunc{
// We handle our own runtime with our own cancellation
WithRuntime(cfg.Runtime),
WithPreventCancellation(),
}
opts = append(opts, cfg.TranspileOptions...)
for _, h := range cfg.ScriptPreTranspileHooks {
script, err = h(script)
if err != nil {
return nil, fmt.Errorf("running script pre-transpile hook: %w", err)
}
}
script, err = TranspileCtx(ctx, strings.NewReader(script), opts...)
if err != nil {
return nil, fmt.Errorf("transpiling script: %w", err)
}
}
for _, h := range cfg.ScriptHooks {
script, err = h(script)
if err != nil {
return nil, fmt.Errorf("running script hook: %w", err)
}
}
result, err = cfg.Runtime.RunString(script)
if err != nil {
if strings.Contains(err.Error(), "context halt") {
err = context.Canceled
}
}
return
}