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Add Custom Directive Support for Fields #543

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merged 20 commits into from
Jan 19, 2023
Merged

Add Custom Directive Support for Fields #543

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5e217c2
Added support of custom directives
eko Apr 8, 2021
fd885f0
simplify tests, improve organization of test file
Dec 22, 2022
da343da
add t.Parellel()
Dec 22, 2022
64aa7b9
remove useless comment
Dec 22, 2022
748ce7a
parallel some more
Dec 22, 2022
0bd7a07
rename
Dec 22, 2022
ddc1b7a
go 1.18 and go mod tidy
Dec 22, 2022
cf821db
Update go.mod
pavelnikolov Dec 24, 2022
77530e9
Update go.mod
pavelnikolov Dec 24, 2022
483881c
Update go.sum
pavelnikolov Dec 24, 2022
54416fd
move directives to separate package
Dec 24, 2022
870991a
newline
Dec 24, 2022
945f124
clean up
Dec 24, 2022
92a4068
more docs
Dec 24, 2022
a1157fa
demo for caching
Dec 28, 2022
3b84a57
Refactoring
pavelnikolov Jan 17, 2023
9d127ce
Add example hasRole directive
pavelnikolov Jan 17, 2023
b290e8b
Pass traceCtx to directive visitors
pavelnikolov Jan 17, 2023
2af43e4
Fix a typo
pavelnikolov Jan 17, 2023
12642b1
Improve documentation
pavelnikolov Jan 19, 2023
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5 changes: 3 additions & 2 deletions directives/visitor.go
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Original file line number Diff line number Diff line change
Expand Up @@ -10,8 +10,9 @@ import (
// see the graphql.DirectiveVisitors() Schema Option
type Visitor interface {
// Before() is always called when the operation includes a directive matching this implementation's name
// When the first return value is true, the field resolver will not be called.
// Errors in Before() will prevent field resolution
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Before(ctx context.Context, directive *types.Directive, input interface{}) error
Before(ctx context.Context, directive *types.Directive, input interface{}) (skipResolver bool, err error)
// After is called if Before() *and* the field resolver do not error
After(ctx context.Context, directive *types.Directive, output interface{}) (interface{}, error)
After(ctx context.Context, directive *types.Directive, output interface{}) (modified interface{}, err error)
}
56 changes: 54 additions & 2 deletions graphql_test.go
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Original file line number Diff line number Diff line change
Expand Up @@ -58,9 +58,9 @@ type customDirectiveVisitor struct {
beforeWasCalled bool
}

func (v *customDirectiveVisitor) Before(ctx context.Context, directive *types.Directive, input interface{}) error {
func (v *customDirectiveVisitor) Before(ctx context.Context, directive *types.Directive, input interface{}) (bool, error) {
v.beforeWasCalled = true
return nil
return false, nil
}

func (v *customDirectiveVisitor) After(ctx context.Context, directive *types.Directive, output interface{}) (interface{}, error) {
Expand All @@ -74,6 +74,30 @@ func (v *customDirectiveVisitor) After(ctx context.Context, directive *types.Dir
return fmt.Sprintf("Directive '%s' modified result: %s", directive.Name.Name, output.(string)), nil
}

type cachedDirectiveVisitor struct {
cachedValue interface{}
}

func (v *cachedDirectiveVisitor) Before(ctx context.Context, directive *types.Directive, input interface{}) (bool, error) {
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s := "valueFromCache"
v.cachedValue = s
return true, nil
}

func (v *cachedDirectiveVisitor) After(ctx context.Context, directive *types.Directive, output interface{}) (interface{}, error) {
return v.cachedValue, nil
}

type cachedDirectiveResolver struct {
t *testing.T
}

func (r *cachedDirectiveResolver) Hello(ctx context.Context, args struct{ FullName string }) string {
r.t.Error("expected cached resolver to not be called, but it was")

return ""
}

type theNumberResolver struct {
number int32
}
Expand Down Expand Up @@ -329,6 +353,34 @@ func TestCustomDirective(t *testing.T) {
}
`,
},
{
Schema: graphql.MustParseSchema(`
directive @cached(
key: String!
) on FIELD_DEFINITION

schema {
query: Query
}

type Query {
hello(full_name: String!): String! @cached(key: "notcheckedintest")
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It would be cool if this key can come from the resolved entity's ID somehow. In a real-world situation we would need to use the ID of that entity or the ID of its parent, for example, the products of a category or the comments of a post. In both of these examples we need to cache by the ID of the parent entity. I wish we could somehow do that.

}
`, &cachedDirectiveResolver{t: t},
graphql.DirectiveVisitors(map[string]directives.Visitor{
"cached": &cachedDirectiveVisitor{},
})),
Query: `
{
hello(full_name: "Full Name")
}
`,
ExpectedResult: `
{
"hello": "valueFromCache"
}
`,
},
})
}

Expand Down
53 changes: 38 additions & 15 deletions internal/exec/exec.go
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Original file line number Diff line number Diff line change
Expand Up @@ -203,7 +203,13 @@ func execFieldSelection(ctx context.Context, r *Request, s *resolvable.Schema, f

res := f.resolver
if f.field.UseMethodResolver() {
var in []reflect.Value
var (
skipResolver bool
in []reflect.Value
callOut []reflect.Value
visitorErr error
modified interface{}
)
if f.field.HasContext {
in = append(in, reflect.ValueOf(traceCtx))
}
Expand All @@ -219,8 +225,7 @@ func execFieldSelection(ctx context.Context, r *Request, s *resolvable.Schema, f
for _, inValue := range in {
values = append(values, inValue.Interface())
}

visitorErr := visitor.Before(ctx, directive, values)
skipResolver, visitorErr = visitor.Before(ctx, directive, values)
if visitorErr != nil {
err := errors.Errorf("%s", visitorErr)
err.Path = path.toSlice()
Expand All @@ -231,27 +236,36 @@ func execFieldSelection(ctx context.Context, r *Request, s *resolvable.Schema, f
}
}

// Call method
callOut := res.Method(f.field.MethodIndex).Call(in)
result = callOut[0]
// Call method unless the Before visitor tells us not to
if !skipResolver {
callOut = res.Method(f.field.MethodIndex).Call(in)
result = callOut[0]
}

// After hook directive visitor (when no error is returned from resolver)
if !f.field.HasError && len(f.field.Directives) > 0 {
for _, directive := range f.field.Directives {
if visitor, ok := r.Visitors[directive.Name.Name]; ok {
modified, visitorErr := visitor.After(ctx, directive, result.Interface())
if (result.IsValid() && !result.IsZero()) && result.CanInterface() {
modified, visitorErr = visitor.After(ctx, directive, result.Interface())
} else {
modified, visitorErr = visitor.After(ctx, directive, nil)
}

if visitorErr != nil {
err := errors.Errorf("%s", visitorErr)
err.Path = path.toSlice()
err.ResolverError = visitorErr
return err
} else {
result = reflect.ValueOf(modified)
}
result = reflect.ValueOf(modified)
}
}
}

if skipResolver {
return nil
}
if f.field.HasError && !callOut[1].IsNil() {
resolverErr := callOut[1].Interface().(error)
err := errors.Errorf("%s", resolverErr)
Expand All @@ -263,6 +277,11 @@ func execFieldSelection(ctx context.Context, r *Request, s *resolvable.Schema, f
return err
}
} else {
var (
skipResolver bool
visitorErr error
modified interface{}
)
// TODO extract out unwrapping ptr logic to a common place
if res.Kind() == reflect.Ptr {
res = res.Elem()
Expand All @@ -271,8 +290,7 @@ func execFieldSelection(ctx context.Context, r *Request, s *resolvable.Schema, f
if len(f.field.Directives) > 0 {
for _, directive := range f.field.Directives {
if visitor, ok := r.Visitors[directive.Name.Name]; ok {
// TODO check that directive arity == 0-that should be an error at schema init time
visitorErr := visitor.Before(ctx, directive, nil)
skipResolver, visitorErr = visitor.Before(ctx, directive, nil)
if visitorErr != nil {
err := errors.Errorf("%s", visitorErr)
err.Path = path.toSlice()
Expand All @@ -282,20 +300,25 @@ func execFieldSelection(ctx context.Context, r *Request, s *resolvable.Schema, f
}
}
}
result = res.FieldByIndex(f.field.FieldIndex)
if !skipResolver {
result = res.FieldByIndex(f.field.FieldIndex)
}
// After hook directive visitor (when no error is returned from resolver)
if !f.field.HasError && len(f.field.Directives) > 0 {
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I don't think that struct resolver fields can ever produce an error but I'm not an expert. Shall we delete this, Pavel?

Suggested change
if !f.field.HasError && len(f.field.Directives) > 0 {
if len(f.field.Directives) > 0 {

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Yes, struct fields cannot produce an error. It doesn't make sense to me to check for one.

for _, directive := range f.field.Directives {
if visitor, ok := r.Visitors[directive.Name.Name]; ok {
modified, visitorErr := visitor.After(ctx, directive, result.Interface())
if (result.IsValid() && !result.IsZero()) && result.CanInterface() {
modified, visitorErr = visitor.After(ctx, directive, result.Interface())
} else {
modified, visitorErr = visitor.After(ctx, directive, nil)
}
if visitorErr != nil {
err := errors.Errorf("%s", visitorErr)
err.Path = path.toSlice()
err.ResolverError = visitorErr
return err
} else {
result = reflect.ValueOf(modified)
}
result = reflect.ValueOf(modified)
}
}
}
Expand Down