Querying `blocks` field on `StructBlock` (in `StreamField`) leads to error message

[tbrlpld]

Hi,

I have just installed the latest Grapple version from master (which should already include https://github.com/GrappleGQL/wagtail-grapple/pull/82). Since it mentioned #54 which was also concerned with the StructBlock https://github.com/GrappleGQL/wagtail-grapple/pull/54#issuecomment-604432979, I thought I would help my issue here. Turns out that is not the case.

The issue is that querying the blocks field on StructBlock leads to error message.

Before I update to the version from GitHub, this seemed to be related to ImageChooserBlock inside the StructBlock and if they have a value or not. But I have tested this now with and without and ImageChooserBlock as a field in the StructBlock and the behavior remains the same.

A query like this

query {
  page(slug: "first-article"){
    id
    ... on BlogPage {
      freeformbody {
        ... on StructBlock {
          id
          blocks {
            id
          }
        }
      }
    }
  }
}

leads to an error like that:

{
  "errors": [
    {
      "message": "string indices must be integers",
      "locations": [
        {
          "line": 8,
          "column": 11
        }
      ],
      "path": [
        "page",
        "freeformbody",
        21,
        "blocks"
      ]
    }
  ],
  "data": {...}
  }
}

And here is the output on the server side:

[29/Jul/2020 05:17:36] "POST /graphql HTTP/1.1" 200 141242
Traceback (most recent call last):
  File "<...>/.venv/lib/python3.7/site-packages/promise/promise.py", line 489, in _resolve_from_executor
    executor(resolve, reject)
  File "<...>/.venv/lib/python3.7/site-packages/promise/promise.py", line 756, in executor
    return resolve(f(*args, **kwargs))
  File "<...>/.venv/lib/python3.7/site-packages/graphql/execution/middleware.py", line 75, in make_it_promise
    return next(*args, **kwargs)
  File "<...>/.venv/src/wagtail-grapple/grapple/types/streamfield.py", line 150, in resolve_blocks
    block = child_blocks[field["type"]]
graphql.error.located_error.GraphQLLocatedError: string indices must be integers

When removing the blocks field from the query, then the response works successfully.

Here is the part of the page definition this issue seems concerned with.

class BlogPage(HeadlessPreviewMixin, Page):
    ...
    freeformbody = StreamField(
        [
            ...
            ('person', blocks.StructBlock([
                ('first_name', blocks.CharBlock()),
                ('last_name', blocks.CharBlock()),
                ('biography', blocks.TextBlock()),
            ], icon='user')),
            ...
        ],
        blank=True,
    )

    graphql_fields = [
        ...
        gpm.GraphQLStreamfield('freeformbody'),
        ...
    ]

I assume this has something to do with the serialization of the StuctBlock child fields.

Are you able to reproduce this behavior?

[zerolab]

@tbrlpld could this have been the same issue as #117, fixed in #118 ?

[tbrlpld]

@zerolab Yes, it does work! Awesome. Thanks for pointing this out!