{
  "_comment": [
    "Inputs only. Expectations are measured -- see record.js.",
    "`$[]`, the all-positional operator. The pinned crud corpus contains no",
    "`$[]` case at all, which is half of why this directory exists: before",
    "the refusal landed, `$[]` overwrote the array it was meant to walk and",
    "nothing external would have noticed."
  ],
  "documents": [
    { "_id": 1, "y": [{ "b": 3 }, { "b": 1 }] },
    { "_id": 2, "y": [] },
    { "_id": 3, "y": [{ "c": [{ "d": 1 }, { "d": 2 }] }, { "c": [{ "d": 3 }] }] }
  ],
  "cases": [
    {
      "description": "every element of the array is written",
      "operation": "updateOne",
      "arguments": {
        "filter": { "_id": 1 },
        "update": { "$set": { "y.$[].b": 9 } }
      }
    },
    {
      "description": "nested $[] is a cross-product over both levels",
      "operation": "updateOne",
      "arguments": {
        "filter": { "_id": 3 },
        "update": { "$set": { "y.$[].c.$[].d": 0 } }
      }
    },
    {
      "description": "$[] over an empty array",
      "operation": "updateOne",
      "arguments": {
        "filter": { "_id": 2 },
        "update": { "$set": { "y.$[].b": 9 } }
      }
    },
    {
      "description": "$inc through $[] adds to every element",
      "operation": "updateOne",
      "arguments": {
        "filter": { "_id": 1 },
        "update": { "$inc": { "y.$[].b": 10 } }
      }
    },
    {
      "description": "$[] as the leaf over an array of scalars",
      "documents": [{ "_id": 1, "y": [1, 2, 3] }],
      "operation": "updateOne",
      "arguments": {
        "filter": {},
        "update": { "$set": { "y.$[]": 0 } }
      }
    },
    {
      "description": "$unset through $[] removes a field from every element",
      "documents": [{ "_id": 1, "y": [{ "b": 1, "e": 1 }, { "b": 2, "e": 2 }] }],
      "operation": "updateOne",
      "arguments": {
        "filter": {},
        "update": { "$unset": { "y.$[].e": "" } }
      }
    },
    {
      "description": "$[] where an element is not a document",
      "documents": [{ "_id": 1, "y": [{ "b": 1 }, 7] }],
      "operation": "updateOne",
      "arguments": {
        "filter": {},
        "update": { "$set": { "y.$[].b": 9 } }
      }
    },
    {
      "description": "updateMany with $[] across every document",
      "operation": "updateMany",
      "arguments": {
        "filter": { "_id": { "$in": [1, 2] } },
        "update": { "$set": { "y.$[].b": 9 } }
      }
    },
    {
      "description": "$[] where the path does not exist",
      "documents": [{ "_id": 1, "z": 1 }],
      "operation": "updateOne",
      "arguments": {
        "filter": {},
        "update": { "$set": { "y.$[].b": 9 } }
      }
    },
    {
      "description": "$[] where the path is not an array",
      "documents": [{ "_id": 1, "y": 5 }],
      "operation": "updateOne",
      "arguments": {
        "filter": {},
        "update": { "$set": { "y.$[].b": 9 } }
      }
    },
    {
      "description": "$[] in first position is refused",
      "operation": "updateOne",
      "arguments": {
        "filter": { "_id": 1 },
        "update": { "$set": { "$[]": 9 } }
      }
    },
    {
      "description": "$[] combined with an identifier in one path",
      "operation": "updateOne",
      "arguments": {
        "filter": { "_id": 3 },
        "update": { "$set": { "y.$[].c.$[j].d": 0 } },
        "arrayFilters": [{ "j.d": 2 }]
      }
    }
  ]
}