04 — Response shaper

Status: Draft
Applies to: Compliance Level 1+

The shaper converts flat relational rows into the nested JSON selection shape. Implementations that only use nested ORM results MAY skip this step if outputs already match the query.

Inputs

1. Query AST / selection tree
2. Zero or more flat rows: Record<string, unknown>[]
3. Join list (ResolvedJoin[]) with path and type

Row key aliases

For a scalar field field on root entity / table prefix nodeName:

Preference	Key form	Example
1	{nodeName}_{field}	user_id, posts_title
2	{nodeName}.{field}	user.id
3	{field}	id (fallback)

For a joined path, replace . in the join path with _ (joinPathAlias):

Path	Alias prefix	Field key
comments	comments	comments_body
comments.author	comments_author	comments_author_name

SQL builders SHOULD emit these aliases so the shaper can find columns unambiguously when the same entity appears twice (e.g. post.author and comments.author).

Nesting rules

1. Walk the selection tree depth-first.
2. For each many join, group child objects by the join entity’s idField (or by full row identity when id is missing) under an array.
3. For each one join, attach a single object or omit / null if no matching columns are present in any row.
4. Dedupe many children when Cartesian products repeat the same id across flat rows.

Example

Flat rows:

[
  {
    "posts_id": 1,
    "posts_title": "Hello",
    "comments_id": 10,
    "comments_body": "Nice",
    "comments_author_name": "Ada"
  },
  {
    "posts_id": 1,
    "posts_title": "Hello",
    "comments_id": 11,
    "comments_body": "Agreed",
    "comments_author_name": "Grace"
  }
]

Shaped (illustrative):

{
  "id": 1,
  "title": "Hello",
  "comments": [
    { "id": 10, "body": "Nice", "author": { "name": "Ada" } },
    { "id": 11, "body": "Agreed", "author": { "name": "Grace" } }
  ]
}

Fixtures

See fixtures/responses.