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exec.go
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exec.go
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package exec
import (
"bytes"
"context"
"encoding/json"
"reflect"
"sync"
"github.com/graph-gophers/graphql-go/errors"
"github.com/graph-gophers/graphql-go/internal/common"
"github.com/graph-gophers/graphql-go/internal/exec/resolvable"
"github.com/graph-gophers/graphql-go/internal/exec/selected"
"github.com/graph-gophers/graphql-go/internal/query"
"github.com/graph-gophers/graphql-go/internal/schema"
"github.com/graph-gophers/graphql-go/log"
pubselected "github.com/graph-gophers/graphql-go/selected"
"github.com/graph-gophers/graphql-go/trace"
)
type Request struct {
selected.Request
Limiter chan struct{}
Tracer trace.Tracer
Logger log.Logger
}
func (r *Request) handlePanic(ctx context.Context) {
if value := recover(); value != nil {
r.Logger.LogPanic(ctx, value)
r.AddError(makePanicError(value))
}
}
func makePanicError(value interface{}) *errors.QueryError {
return errors.Errorf("graphql: panic occurred: %v", value)
}
func (r *Request) Execute(ctx context.Context, s *resolvable.Schema, op *query.Operation) ([]byte, []*errors.QueryError) {
var out bytes.Buffer
func() {
defer r.handlePanic(ctx)
sels := selected.ApplyOperation(&r.Request, s, op)
r.execSelections(ctx, sels, nil, s.Resolver, &out, op.Type == query.Mutation)
}()
if err := ctx.Err(); err != nil {
return nil, []*errors.QueryError{errors.Errorf("%s", err)}
}
return out.Bytes(), r.Errs
}
type fieldToExec struct {
field *selected.SchemaField
sels []selected.Selection
resolver reflect.Value
out *bytes.Buffer
}
func (r *Request) execSelections(ctx context.Context, sels []selected.Selection, path *pathSegment, resolver reflect.Value, out *bytes.Buffer, serially bool) {
async := !serially && selected.HasAsyncSel(sels)
var fields []*fieldToExec
collectFieldsToResolve(sels, resolver, &fields, make(map[string]*fieldToExec))
if async {
var wg sync.WaitGroup
wg.Add(len(fields))
for _, f := range fields {
go func(f *fieldToExec) {
defer wg.Done()
defer r.handlePanic(ctx)
f.out = new(bytes.Buffer)
execFieldSelection(ctx, r, f, &pathSegment{path, f.field.Alias}, true)
}(f)
}
wg.Wait()
}
out.WriteByte('{')
for i, f := range fields {
if i > 0 {
out.WriteByte(',')
}
out.WriteByte('"')
out.WriteString(f.field.Alias)
out.WriteByte('"')
out.WriteByte(':')
if async {
out.Write(f.out.Bytes())
continue
}
f.out = out
execFieldSelection(ctx, r, f, &pathSegment{path, f.field.Alias}, false)
}
out.WriteByte('}')
}
func collectFieldsToResolve(sels []selected.Selection, resolver reflect.Value, fields *[]*fieldToExec, fieldByAlias map[string]*fieldToExec) {
for _, sel := range sels {
switch sel := sel.(type) {
case *selected.SchemaField:
field, ok := fieldByAlias[sel.Alias]
if !ok { // validation already checked for conflict (TODO)
field = &fieldToExec{field: sel, resolver: resolver}
fieldByAlias[sel.Alias] = field
*fields = append(*fields, field)
}
field.sels = append(field.sels, sel.Sels...)
case *selected.TypenameField:
sf := &selected.SchemaField{
Field: resolvable.MetaFieldTypename,
Alias: sel.Alias,
FixedResult: reflect.ValueOf(typeOf(sel, resolver)),
}
*fields = append(*fields, &fieldToExec{field: sf, resolver: resolver})
case *selected.TypeAssertion:
out := resolver.Method(sel.MethodIndex).Call(nil)
if !out[1].Bool() {
continue
}
collectFieldsToResolve(sel.Sels, out[0], fields, fieldByAlias)
default:
panic("unreachable")
}
}
}
func typeOf(tf *selected.TypenameField, resolver reflect.Value) string {
if len(tf.TypeAssertions) == 0 {
return tf.Name
}
for name, a := range tf.TypeAssertions {
out := resolver.Method(a.MethodIndex).Call(nil)
if out[1].Bool() {
return name
}
}
return ""
}
func execFieldSelection(ctx context.Context, r *Request, f *fieldToExec, path *pathSegment, applyLimiter bool) {
if applyLimiter {
r.Limiter <- struct{}{}
}
var result reflect.Value
var err *errors.QueryError
traceCtx, finish := r.Tracer.TraceField(ctx, f.field.TraceLabel, f.field.TypeName, f.field.Name, !f.field.Async, f.field.Args)
defer func() {
finish(err)
}()
err = func() (err *errors.QueryError) {
defer func() {
if panicValue := recover(); panicValue != nil {
r.Logger.LogPanic(ctx, panicValue)
err = makePanicError(panicValue)
err.Path = path.toSlice()
}
}()
if f.field.FixedResult.IsValid() {
result = f.field.FixedResult
return nil
}
if err := traceCtx.Err(); err != nil {
return errors.Errorf("%s", err) // don't execute any more resolvers if context got cancelled
}
if f.field.MethodIndex != -1 {
var in []reflect.Value
if f.field.HasContext {
// lazily evaluate
resCtx := context.WithValue(traceCtx, pubselected.ContextKey, selectedFields(f.sels))
in = append(in, reflect.ValueOf(resCtx))
}
if f.field.ArgsPacker != nil {
in = append(in, f.field.PackedArgs)
}
callOut := f.resolver.Method(f.field.MethodIndex).Call(in)
result = callOut[0]
if f.field.HasError && !callOut[1].IsNil() {
resolverErr := callOut[1].Interface().(error)
err := errors.Errorf("%s", resolverErr)
err.Path = path.toSlice()
err.ResolverError = resolverErr
return err
}
} else {
// TODO extract out unwrapping ptr logic to a common place
res := f.resolver
if res.Kind() == reflect.Ptr {
res = res.Elem()
}
result = res.Field(f.field.FieldIndex)
}
return nil
}()
if applyLimiter {
<-r.Limiter
}
if err != nil {
r.AddError(err)
f.out.WriteString("null") // TODO handle non-nil
return
}
r.execSelectionSet(traceCtx, f.sels, f.field.Type, path, result, f.out)
}
func (r *Request) execSelectionSet(ctx context.Context, sels []selected.Selection, typ common.Type, path *pathSegment, resolver reflect.Value, out *bytes.Buffer) {
t, nonNull := unwrapNonNull(typ)
switch t := t.(type) {
case *schema.Object, *schema.Interface, *schema.Union:
if resolver.Kind() == reflect.Ptr && resolver.IsNil() {
if nonNull {
panic(errors.Errorf("got nil for non-null %q", t))
}
out.WriteString("null")
return
}
r.execSelections(ctx, sels, path, resolver, out, false)
return
}
if !nonNull {
if resolver.IsNil() {
out.WriteString("null")
return
}
resolver = resolver.Elem()
}
switch t := t.(type) {
case *common.List:
l := resolver.Len()
if selected.HasAsyncSel(sels) {
var wg sync.WaitGroup
wg.Add(l)
entryouts := make([]bytes.Buffer, l)
for i := 0; i < l; i++ {
go func(i int) {
defer wg.Done()
defer r.handlePanic(ctx)
r.execSelectionSet(ctx, sels, t.OfType, &pathSegment{path, i}, resolver.Index(i), &entryouts[i])
}(i)
}
wg.Wait()
out.WriteByte('[')
for i, entryout := range entryouts {
if i > 0 {
out.WriteByte(',')
}
out.Write(entryout.Bytes())
}
out.WriteByte(']')
return
}
out.WriteByte('[')
for i := 0; i < l; i++ {
if i > 0 {
out.WriteByte(',')
}
r.execSelectionSet(ctx, sels, t.OfType, &pathSegment{path, i}, resolver.Index(i), out)
}
out.WriteByte(']')
case *schema.Scalar:
v := resolver.Interface()
data, err := json.Marshal(v)
if err != nil {
panic(errors.Errorf("could not marshal %v", v))
}
out.Write(data)
case *schema.Enum:
out.WriteByte('"')
out.WriteString(resolver.String())
out.WriteByte('"')
default:
panic("unreachable")
}
}
func unwrapNonNull(t common.Type) (common.Type, bool) {
if nn, ok := t.(*common.NonNull); ok {
return nn.OfType, true
}
return t, false
}
// lazily add selection fields in context
func selectedFields(sels []selected.Selection) pubselected.SelectedFields {
return func() []pubselected.SelectedField {
return selectionToSelectedFields(sels)
}
}
func selectionToSelectedFields(sels []selected.Selection) []pubselected.SelectedField {
var selectedFields []pubselected.SelectedField
selsLen := len(sels)
if selsLen != 0 {
selectedFields = make([]pubselected.SelectedField, 0, selsLen)
for _, sel := range sels {
selField, ok := sel.(*selected.SchemaField)
if ok {
selectedFields = append(selectedFields, pubselected.SelectedField{
Name: selField.Field.Name,
Args: selField.Args,
Selected: selectionToSelectedFields(selField.Sels),
})
}
}
}
return selectedFields
}
type pathSegment struct {
parent *pathSegment
value interface{}
}
func (p *pathSegment) toSlice() []interface{} {
if p == nil {
return nil
}
return append(p.parent.toSlice(), p.value)
}