Map projection with a function-call computed field may return only the function result instead of a map #4184

ArcadeDB version
Observed on Docker images:

• arcadedata/arcadedb:26.3.2
• arcadedata/arcadedb:26.4.1-SNAPSHOT
• arcadedata/arcadedb:26.4.2

Environment

• Host OS: Windows 10
• Architecture: x86_64
• Deployment: Docker
• ArcadeDB endpoint: HTTP /api/v1/command/arcade
• Request mode matches ArcadeDB Studio:
  • language: opencypher
  • serializer: studio
• Differential comparison target: Neo4j Docker neo4j:latest

Describe the bug
ArcadeDB may evaluate a node map projection incorrectly when one computed field is defined by a function call.

Instead of returning the projected map, ArcadeDB returns only the function result.

In the minimized repro below, Neo4j correctly returns:

{name: 'Alice', upperName: 'ALICE'}

ArcadeDB returns only:

ALICE

So the projection target p and the other projected fields disappear entirely.

This is not just a column-name issue.
Even with an explicit AS proj alias, the value itself is wrong.

To Reproduce

Setup:

CREATE (:Person {name:'Alice'});

Query:

MATCH (p:Person)
RETURN p {.name, upperName: toUpper(p.name)} AS proj;

Expected behavior
Observed Neo4j result:

{name: 'Alice', upperName: 'ALICE'}

ArcadeDB should return the same projected map.

Actual behavior
Observed ArcadeDB result on all tested versions:

ALICE

So the function result replaces the whole map projection.

Additional function-call variant
The same bad behavior also appears with size(...):

MATCH (p:Person)
WITH p, [] AS friends
RETURN p {.name, friendCount: size(friends)} AS proj;

Observed results:

• Neo4j:

{name: 'Alice', friendCount: 0}

• ArcadeDB latest / 26.3.2 / 26.4.1-SNAPSHOT / 26.4.2:

0

So this is not specific to one string function.
More generally, a computed field based on a function call can replace the entire projection result.

Control cases

A plain map projection without a computed field works:

MATCH (p:Person)
RETURN p {.name} AS proj;

Observed result on Neo4j and all tested ArcadeDB versions:

{name: 'Alice'}

A computed field with a constant value also works:

MATCH (p:Person)
RETURN p {.name, friendCount: 0} AS proj;

Observed result on Neo4j and all tested ArcadeDB versions:

{name: 'Alice', friendCount: 0}

A computed field with a non-function expression also works:

MATCH (p:Person)
RETURN p {.name, nameCopy: p.name + ''} AS proj;

Observed result on Neo4j and all tested ArcadeDB versions:

{name: 'Alice', nameCopy: 'Alice'}

So the bad behavior is not about computed fields in general.
The failure starts when the computed field expression is a function call such as:

• toUpper(p.name)
• size(friends)

Original differential seed

This family first resurfaced in the current feature-only random differential in a noisier path-and-list variant:

MATCH (p:Person)
OPTIONAL MATCH (p)-[:KNOWS|FRIEND*1..2]->(q:Person)
WITH p, collect(DISTINCT q) AS friends, [x IN [1, 2, 3] WHERE false | x] AS emptyList
RETURN p {.name, friendCount: size(friends), emptyList}
ORDER BY p.name;

Observed results:

• Neo4j:

{name: 'Alice', friendCount: 0, emptyList: []}
{name: 'Bob', friendCount: 0, emptyList: []}
{name: 'Charlie', friendCount: 0, emptyList: []}

• ArcadeDB 26.4.2:

0
0
0

Direct minimization shows that the optional match and the extra empty-list field are not required.
The smaller root cause is the function-call computed field inside the map projection.