Fix SQL syntax error when select contains only false fields (including nested queries)

[Copilot]

Queries with select: { id: false } generate invalid SQL (SELECT FROM "User") when all fields are explicitly excluded, causing database errors. This PR fixes the issue for both top-level and nested relation queries.

Changes

Core fix (packages/orm/src/client/crud/operations/base.ts):

• Early return [] from read() when all select fields are false
• Avoids SQL generation for impossible field selection
• Existing FindOperationHandler transforms this correctly: [] for findMany, null for findFirst/findUnique

Nested query fix (packages/orm/src/client/crud/dialects/lateral-join-dialect-base.ts and packages/orm/src/client/result-processor.ts):

• Added check in buildRelationObjectArgs() to detect when all select fields are false in nested relations
• Added filtering in processRelation() to remove empty objects from array relations
• Ensures nested queries with only false fields return empty arrays instead of arrays of empty objects

Test coverage (tests/e2e/orm/client-api/find.test.ts):

• Added test cases covering findMany, findFirst, and findUnique with only false fields
• Added test case for nested queries with only false fields in select

Example

// Before: SQL error
await db.user.findMany({ select: { id: false } });
// Error: near "from": syntax error

// After: Returns empty result
await db.user.findMany({ select: { id: false } });     // []
await db.user.findFirst({ select: { id: false } });    // null
await db.user.findUnique({ 
  where: { id: '1' }, 
  select: { id: false } 
});  // null

// Nested queries also work correctly
await db.user.findUnique({
  where: { id: '1' },
  select: {
    id: true,
    email: true,
    posts: { select: { id: false } }
  }
});  // { id: '1', email: 'test@test.com', posts: [] }

Original prompt

---

This section details on the original issue you should resolve

<issue_title>[Bug]: Query failed if there is only false field in the select params</issue_title>
<issue_description>The below code will show error:

    await db.user.findMany({
      select: {
        id: false,
      },
    }),

    reason: 'db-query-error',
    model: undefined,
    dbErrorCode: 'SQLITE_ERROR',
    dbErrorMessage: 'near "from": syntax error',
    rejectedByPolicyReason: undefined,
    sql: 'select from "User" ',

It generate a select statement without any field to be selected which cause the SQL error. </issue_description>

<agent_instructions>In this case direclty return an empty object</agent_instructions>

Comments on the Issue (you are @copilot in this section)

• Fixes [Bug]: Query failed if there is only false field in the select params zenstack#2344

---

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[jiashengguo]

@copilot
Add the case that this false select is in the nested query

[Copilot]

Added test case for nested queries with only false fields in commit 3adea0a. The fix now handles both top-level and nested relation queries properly - empty objects are filtered out in the result processor for array relations.

[Copilot]

Pull request overview

This PR fixes a SQL syntax error that occurred when queries used select with only false values (e.g., select: { id: false }), which would generate invalid SQL like SELECT FROM "User".

Changes:

• Added early return in read() method to handle cases where all select fields are explicitly set to false
• Added comprehensive test coverage for findMany, findFirst, and findUnique operations with only false select fields

Reviewed changes

Copilot reviewed 2 out of 2 changed files in this pull request and generated no comments.

File	Description
packages/orm/src/client/crud/operations/base.ts	Adds validation check to return empty array when all select fields are false, preventing invalid SQL generation
tests/e2e/orm/client-api/find.test.ts	Adds test case verifying correct behavior (empty array for findMany, null for findFirst/findUnique) when all select fields are false

---

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[ymc9]

@copilot could you check Prisma ORM's behavior for this usage? For both top-level select and nested relation select.

[Copilot]

@copilot could you check Prisma ORM's behavior for this usage? For both top-level select and nested relation select.

I tested Prisma ORM's behavior with select containing only false fields:

Prisma ORM behavior:

• Top-level select: Throws validation error: "The select statement for type X needs at least one truthy value"
• Nested relation select: Same error for the nested relation: "The select statement for type Post needs at least one truthy value"

Current implementation (this PR):

• Top-level select: Returns empty array for findMany, null for findFirst/findUnique
• Nested relation select: Returns empty array for relation fields

Should we align with Prisma's behavior and throw a validation error instead? This would be a breaking change from the current implementation but would match Prisma's API expectations.

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