How do you write a test for GetPreloads from the docs, given it expects an OperationContext?

[AndrewRayCode]

What happened?

I'm writing a GraphQL service, that itself calls down to an underlying GraphQL service. To support this, I want to read the fields passed to my service, so I can dynamically build the query to send to the underlying service for only the fields needed.

The documentation has an example of how to do this with the GetPreloads function.

This function is working when I perform a live query through my server. However, in my test, I'm calling the resolver more directly, something like:

	httpClient := http.Client{}
	gock.InterceptClient(&httpClient)
	client := gateway{
		gqlClient:   generated.NewClient(&httpClient, endpoint),
	}

	input = graph.MyInput{ SomeFIeld: "SomeValue" }
	res, err := client.MyQuery(context.Background(), &input)

When I run this as is, I get a panic from gqlgen:

panic: missing operation context [recovered]
        panic: missing operation context

goroutine 37 [running]:
testing.tRunner.func1.1(0x1694120, 0x184afd0)
        GOROOT/src/testing/testing.go:1057 +0x30d
testing.tRunner.func1(0xc000276a80)
        GOROOT/src/testing/testing.go:1060 +0x41a
panic(0x1694120, 0x184afd0)
        GOROOT/src/runtime/panic.go:969 +0x175
github.com/99designs/gqlgen/graphql.GetOperationContext(0x1867980, 0xc0002f6240, 0x1c7b798)
        external/com_github_99designs_gqlgen/graphql/context_operation.go:58 +0x9e

So I set out trying to build a context that would satisfy the underlying requirements. I've tried this:

		graphql.WithOperationContext(context.Background(), &graphql.OperationContext{
			RawQuery:             "query A { fields { field } }",
			OperationName:        "Hello",
			Variables:            map[string]interface{}{},
			DisableIntrospection: false,
		}),

This feels like I need to re-create the query to make the test work. This code also raises a nil pointer:

panic: runtime error: invalid memory address or nil pointer dereference [recovered]
        panic: runtime error: invalid memory address or nil pointer dereference
[signal SIGSEGV: segmentation violation code=0x1 addr=0x28 pc=0x1578f74]

goroutine 25 [running]:
testing.tRunner.func1.1(0x16cb680, 0x1c37b90)
        GOROOT/src/testing/testing.go:1057 +0x30d
testing.tRunner.func1(0xc000103200)
        GOROOT/src/testing/testing.go:1060 +0x41a
panic(0x16cb680, 0x1c37b90)
        GOROOT/src/runtime/panic.go:969 +0x175
github.com/99designs/gqlgen/graphql.CollectFieldsCtx(0x1867ae0, 0xc0002f62a0, 0x0, 0x0, 0x0, 0xc000185c70, 0x100fc70, 0xc0002f62a0)
        external/com_github_99designs_gqlgen/graphql/context_operation.go:76 +0xb4

I'm brand new to Go and this library. If this question is more appropriate on StackOverflow I'm happy to ask it there. Since the example function came from the docs, I figured I'd start here to see if there was some official way to make these functions testable for calling the resolvers themselves.

versions

• gqlgen version v0.13.0
• go version 1.15

[nicolaseckhart]

Did you ever manage to find a solution for this issue?

[fgauchet]

I got this test to pass:

func TestGetPreloads(t *testing.T) {
	t.Run("Context with fields", func(t *testing.T) {
		ctx := graphql.WithOperationContext(context.Background(), &graphql.OperationContext{})
		ctx = graphql.WithFieldContext(ctx, &graphql.FieldContext{
			Field: graphql.CollectedField{
				Selections: ast.SelectionSet{
					&ast.Field{
						Name: "field_1",
						SelectionSet: ast.SelectionSet{
							&ast.Field{
								Name: "field_a",
							},
						},
					},
					&ast.Field{
						Name: "field_2",
					},
				},
			},
		})
		result := preloads.GetPreloads(ctx)
		expected := []string{"field_1", "field_1.field_a", "field_2"}
		if !reflect.DeepEqual(result, expected) {
			t.Errorf("expected %v, got %v", expected, result)
		}
	})
}