feat(GraphQL): add selection set of query to the body of lambda request.

[minhaj-shakeel]

Fixes DGRAPH-3180

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This change is 

[abhimanyusinghgaur]

Reviewed 2 of 4 files at r1.
Reviewable status: 2 of 4 files reviewed, 7 unresolved discussions (waiting on @minhaj-shakeel and @pawanrawal)

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graphql/e2e/common/lambda.go, line 162 at r1 (raw file):

lambdaOnQueryUsingDql

1. seems we can merge this into the above lambdaOnQueryUsingDql test. Also, need to update the lambda script files to make use of the info for this query.
2. We should also add a test for a lambda field that returns an object, there is no such test yet. So that we can test that nested filters are propagated for lambda fields as well.

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graphql/schema/custom_http.go, line 197 at r1 (raw file):

*fldValue

maybe just make it an interface{} because there can be cases when the argument value comes from a variable, then the Raw would contain $varName and not the actual value of the $varName.
Also, since Raw is a string so even Int values will be serialized as string, resulting in issues for the users.
By using interface{} we can avoid all that,

OR we can go the way we saw in the Apollo code.

OR just an extension of the interface{} approach, we can use f.ArgumentMap() for the root lambda field, and then don't need to create any struct for args here. fldArgumentList will just be a []map[string]interface{} then. Maybe in a similar manner, we won't need any other structs as well.

I prefer the 3rd one, but let's discuss it tomorrow.

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graphql/schema/custom_http.go, line 220 at r1 (raw file):

type fldSelectionSet []fldSelection
type fldSelection interface{}

shouldn't this just be?

type fldSelectionSet []*selectionField

Also, let's cleanup the fld prefix from every struct. We can name them something better. For example, this one can just be selectionSet.
And, add JSON tags within every struct, which ensures that if we rename a field, we don't change the output JSON.

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graphql/schema/custom_http.go, line 246 at r1 (raw file):

}

func convert(f ast.Field) selectionField {

1. maybe rename this function as getInfo(), and it returns an Info object.
2. Just thinking along what we saw in the apollo resolvers, maybe we should nest the field inside the info:

{
  "info": {
    "field": <the current output returned by convert here>
  }
}

so that if we later want to add the returnType in info, we can do that.

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graphql/schema/custom_http.go, line 253 at r1 (raw file):

outField.SelectionSet = make(fldSelectionSet, len(f.SelectionSet))

can be moved within the initializer

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graphql/schema/custom_http.go, line 255 at r1 (raw file):

*sel.(*ast.Field)

convert can directly accept a pointer, instead of dereferencing, creating a copy and passing that every time.

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graphql/schema/wrappers.go, line 205 at r1 (raw file):

GetField() ast.Field

let's not expose the ast.Field to other packages, rather move the convert logic to wrappers. And actually, as the convert logic is within the same package, we shouldn't even be needing this method. So, rather remove this.

[maaft]

Hey,

I'm eagerly waiting for this feature. Why is it still blocked for merging?

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