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feat(policy): field-level update policies on M2M relation fields #2858

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f9b9f31
feat(policy): field-level update policies on M2M relation fields
Sep 25, 2026
dad0f79
fix(policy): address review comments on M2M field-level update policies
Sep 25, 2026
d7fd652
fix(policy): aggregate M2M delete precheck to a single row
Sep 25, 2026
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46 changes: 46 additions & 0 deletions packages/language/src/utils.ts
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Original file line number Diff line number Diff line change
Expand Up @@ -166,6 +166,52 @@ export function isRelationshipField(field: DataField) {
return isDataModel(field.type.reference?.ref);
}

/**
* Returns the name of the relation the given field belongs to, as declared in its `@relation`
* attribute, or `undefined` if the field has no `@relation` attribute or no explicit name.
*/
function getRelationName(field: DataField): string | undefined {

@ymc9 ymc9 Oct 5, 2026

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The "ts-schema-generator.ts" file has a member getRelationName doing the same thing but more robust. Shall we move that implementation here and avoid the duplicate?

const relAttr = field.attributes.find((attr) => attr.decl.ref?.name === '@relation');
if (!relAttr) {
return undefined;
}
for (const arg of relAttr.args) {
if (!arg.name || arg.name === 'name') {
if (isStringLiteral(arg.value)) {
return arg.value.value;
}
}
}
return undefined;
}

/**
* Returns if the given field is a many-to-many relation field, i.e. a relation field that is an
* array and whose opposite relation field on the referenced model (belonging to the same relation)
* is also an array referencing back to the containing model.
*/
export function isManyToManyField(field: DataField) {
if (!isRelationshipField(field) || !field.type.array) {
return false;
}

const oppositeModel = field.type.reference!.ref as DataModel;
const containingModel = field.$container as DataModel;
const relationName = getRelationName(field);

return getAllFields(oppositeModel).some((f) => {
if (f === field || !f.type.array || f.type.reference?.ref?.name !== containingModel.name) {
return false;
}
// if the field declares an explicit relation name, the opposite field must belong to the
// same relation; otherwise any array field referencing back is the opposite
if (relationName !== undefined) {
return getRelationName(f) === relationName;
}
return true;

@ymc9 ymc9 Oct 5, 2026

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I believe this condition is too loose here and it'll allow a false negative for the following case (field bars accidentally matching opposite field foos even though foos is a relation with a different name):

model Foo {
    id     Int   @id
    bars   Bar[] @allow('update', true)
    bar2   Bar   @relation("other", fields: [bar2Id], references: [id])
    bar2Id Int
}

model Bar {
    id    Int @id
    foo   Foo   @relation(fields: [fooId], references: [id])
    fooId Int
    foos  Foo[] @relation("other")
}

@ymc9 ymc9 Oct 5, 2026

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return getRelationName(f) === relationName should be good enough.

});
}

/**
* Returns if the given field is a computed field.
*/
Expand Down
15 changes: 12 additions & 3 deletions packages/language/src/validators/attribute-application-validator.ts
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Expand Up @@ -38,6 +38,7 @@ import {
isComputedField,
isDataFieldReference,
isDelegateModel,
isManyToManyField,
isNativeTypeMappingAttribute,
isRelationshipField,
mapBuiltinTypeToExpressionType,
Expand Down Expand Up @@ -348,18 +349,26 @@ export default class AttributeApplicationValidator implements AstValidator<Attri
});
return;
}
this.validatePolicyKinds(kind, ['read', 'update', 'all'], attr, accept);
const kinds = this.validatePolicyKinds(kind, ['read', 'update', 'all'], attr, accept);

const expr = attr.args[1]?.value;
if (expr && AstUtils.streamAst(expr).some((node) => isBeforeInvocation(node))) {
accept('error', `"before()" is not allowed in field-level policies`, { node: expr });
}

// relation fields are not allowed
// relation fields are not allowed, except for many-to-many fields which only support 'update'
const field = attr.$container as DataField;

if (isRelationshipField(field)) {
accept('error', `Field-level policies are not allowed for relation fields.`, { node: attr });
if (isManyToManyField(field)) {
if (kinds.some((k) => k !== 'update')) {
accept('error', `Only 'update' policies are allowed on many-to-many relation fields`, {
node: attr,
});
}
} else {
accept('error', `Field-level policies are not allowed for relation fields.`, { node: attr });

@ymc9 ymc9 Oct 5, 2026

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Shall we update this error to "Field-level policies are only allowed for implicit many-to-many relation fields"?

}
}

if (isComputedField(field)) {
Expand Down
165 changes: 165 additions & 0 deletions packages/language/test/attribute-application.test.ts
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Expand Up @@ -370,6 +370,171 @@ describe('Attribute application validation tests', () => {
);
});

it('accepts update field-level policy on many-to-many relation fields', async () => {
await loadSchema(`
datasource db {
provider = 'sqlite'
url = 'file:./dev.db'
}

model Foo {
id Int @id @default(autoincrement())
bars Bar[]
@@allow('all', true)
}

model Bar {
id Int @id @default(autoincrement())
foos Foo[] @allow('update', true)
@@allow('all', true)
}
`);
});

it('accepts deny update field-level policy on many-to-many relation fields', async () => {
await loadSchema(`
datasource db {
provider = 'sqlite'
url = 'file:./dev.db'
}

model Foo {
id Int @id @default(autoincrement())
bars Bar[]
@@allow('all', true)
}

model Bar {
id Int @id @default(autoincrement())
foos Foo[] @deny('update', false)
@@allow('all', true)
}
`);
});

it('rejects read field-level policy on many-to-many relation fields', async () => {
await loadSchemaWithError(
`
datasource db {
provider = 'sqlite'
url = 'file:./dev.db'
}

model Foo {
id Int @id @default(autoincrement())
bars Bar[]
@@allow('all', true)
}

model Bar {
id Int @id @default(autoincrement())
foos Foo[] @allow('read', true)
@@allow('all', true)
}
`,
`Only 'update' policies are allowed on many-to-many relation fields`,
);
});

it('rejects all field-level policy on many-to-many relation fields', async () => {
await loadSchemaWithError(
`
datasource db {
provider = 'sqlite'
url = 'file:./dev.db'
}

model Foo {
id Int @id @default(autoincrement())
bars Bar[]
@@allow('all', true)
}

model Bar {
id Int @id @default(autoincrement())
foos Foo[] @allow('all', true)
@@allow('all', true)
}
`,
`Only 'update' policies are allowed on many-to-many relation fields`,
);
});

it('rejects comma-separated kinds including non-update on many-to-many relation fields', async () => {
await loadSchemaWithError(
`
datasource db {
provider = 'sqlite'
url = 'file:./dev.db'
}

model Foo {
id Int @id @default(autoincrement())
bars Bar[]
@@allow('all', true)
}

model Bar {
id Int @id @default(autoincrement())
foos Foo[] @allow('read, update', true)
@@allow('all', true)
}
`,
`Only 'update' policies are allowed on many-to-many relation fields`,
);
});

it('rejects update field-level policy on one-to-many relation fields', async () => {
await loadSchemaWithError(
`
datasource db {
provider = 'sqlite'
url = 'file:./dev.db'
}

model Foo {
id Int @id @default(autoincrement())
bar Bar @relation(fields: [barId], references: [id])
barId Int
@@allow('all', true)
}

model Bar {
id Int @id @default(autoincrement())
foos Foo[] @allow('update', true)
@@allow('all', true)
}
`,
`Field-level policies are not allowed for relation fields`,
);
});

it('rejects update field-level policy on one-to-many relation fields when a separate m2m relation exists', async () => {
await loadSchemaWithError(
`
datasource db {
provider = 'sqlite'
url = 'file:./dev.db'
}

model Foo {
id Int @id @default(autoincrement())
bar Bar @relation("one-to-many", fields: [barId], references: [id]) @allow('update', true)
barId Int
bars Bar[] @relation("m2m")
@@allow('all', true)
}

model Bar {
id Int @id @default(autoincrement())
foos Foo[] @relation("m2m")
@@allow('all', true)
}
`,
`Field-level policies are not allowed for relation fields`,
);
});

it('rejects field-level policy on computed fields', async () => {
await loadSchemaWithError(
`
Expand Down
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