feat(amplify_api): GraphQL Query Helper - List

[Equartey]

Issue #, if available:
Partial implementation of GraphQL model helper feature #308.

Description of changes:
This adds ModelQueries.list(), allows for proper response decoding of PaginatedResults, and relevant unit tests.

By submitting this pull request, I confirm that you can use, modify, copy, and redistribute this contribution, under the terms of your choice.

[codecov-commenter]

Codecov Report

Merging #771 (8c12a4d) into feature/graphql_helpers (5c080aa) will increase coverage by 0.07%.
The diff coverage is 73.52%.

@@                     Coverage Diff                     @@
##           feature/graphql_helpers     #771      +/-   ##
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+ Coverage                    69.52%   69.59%   +0.07%     
===========================================================
  Files                          269      271       +2     
  Lines                         8921     8950      +29     
  Branches                       361      361              
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+ Hits                          6202     6229      +27     
- Misses                        2587     2589       +2     
  Partials                       132      132              

Flag	Coverage Δ
android-unit-tests	63.35% <ø> (ø)
flutter-unit-tests	62.01% <73.52%> (+0.42%)	⬆️
ios-unit-tests	75.49% <ø> (ø)

Flags with carried forward coverage won't be shown. Click here to find out more.

Impacted Files	Coverage Δ
...ify_api/lib/src/graphql/paginated_result_impl.dart	20.00% <20.00%> (ø)
...api/lib/src/graphql/paginated_model_type_impl.dart	91.66% <91.66%> (ø)
packages/amplify_api/lib/model_queries.dart	100.00% <100.00%> (ø)
...y_api/lib/src/graphql/graphql_request_factory.dart	80.70% <100.00%> (+8.77%)	⬆️
...ify_api/lib/src/graphql/model_queries_factory.dart	100.00% <100.00%> (+28.57%)	⬆️

[dnys1]

Looking pretty snazzy! 😄

General comments:

• Let's make all constructors const and fields final when possible (a good rule of thumb)

I'm also going to recommend changing gears a bit and removing documentArgs from the document build step. Ideally, when building the document, we just look at the schema to see what it accepts for input. We're constructing a generic document, essentially, which can be used for any set of variable values (and this will help with caching later, too). The values for those inputs are passed separately in the GraphQL request, and then the server looks at both to do validation and build the actual query.

Example

A user requests a listTodo operation.

Schema:

type Todo @model {
  id: ID!
  title: String!
  description: String
}

type Query {
  listTodos(filter: ModelTodoFilterInput, limit: Int, nextToken: String): ModelTodoConnection
}

Document we build:

query listTodos($filter: ModelTodoFilterInput, $limit: Int, $nextToken: String) {
  listTodos(filter: $filter, limit: $limit, nextToken: $nextToken) {
    nextToken
    items {
      id
      title
      description
    }
  }
}

Variables (JSON) - nullable variables can be omitted or included as null:

{
  "limit": 100,
  "nextToken": null
}

[dnys1]

Booya 😎

[ragingsquirrel3]

🚢 it ! Great job.

[rahul-readwhere]

Hello ,
I am just curious to know, you mentioned ModelTodoFilterInput in your doc. But I am not able to get this in my schema for any model. Am I missing any update?

[ragingsquirrel3]

@rahul-readwhere were you not able to find the ModelTodoFilterInput in your local schema or in the version you see in the AppSync Console? For a small example I have, I noticed that the ModelTodoFilterInput is in the the schema on AWS AppSync Console under AWS AppSync > [backendName] > Schema. For my case, this was created by Amplify when setting up the API resource in my app, which I created from a very basic schema type Blog @model { id: ID!\n name: String!\n createdAt: AWSDate }. More info about that can be found in https://docs.aws.amazon.com/appsync/latest/devguide/provision-from-schema.html