probo/contrib/claude/graphql.md

GraphQL (Go Backend — gqlgen)

Schema-first GraphQL using gqlgen. The schema is hand-written; Go types and resolvers are generated.

Connection types and @goModel

Always define a custom Go type for connection types using the @goModel directive. The model path points to the types package for the relevant API. The totalCount field must use @goField(forceResolver: true). Edge types do not need @goModel.

type VendorConnection
    @goModel(
        model: "go.probo.inc/probo/pkg/server/api/console/v1/types.VendorConnection"
    ) {
    totalCount: Int! @goField(forceResolver: true)
    edges: [VendorEdge!]!
    pageInfo: PageInfo!
}

type VendorEdge {
    cursor: CursorKey!
    node: Vendor!
}

Without @goModel, gqlgen generates a default struct that lacks the custom fields (ParentID, Resolver, Filter) needed by the pagination resolvers.

Enums and @goModel / @goEnum

Map GraphQL enums to existing Go types using @goModel on the enum and @goEnum on each value:

enum VendorOrderField
    @goModel(model: "go.probo.inc/probo/pkg/coredata.VendorOrderField") {
    CREATED_AT
        @goEnum(value: "go.probo.inc/probo/pkg/coredata.VendorOrderFieldCreatedAt")
    NAME
        @goEnum(value: "go.probo.inc/probo/pkg/coredata.VendorOrderFieldName")
}

Schema directives

Directive	Target	Purpose
@goModel(model: "...")	OBJECT, ENUM, INPUT_OBJECT, SCALAR, INTERFACE, UNION	Map GraphQL type to existing Go type
@goEnum(value: "...")	ENUM_VALUE	Map enum value to Go constant
@goField(forceResolver: true)	FIELD_DEFINITION	Force a resolver function instead of struct field
@goField(name: "...")	FIELD_DEFINITION, INPUT_FIELD_DEFINITION	Override Go field name
@goField(omittable: true)	INPUT_FIELD_DEFINITION	Use graphql.Omittable[T] for distinguishing null vs absent

Cursor pagination schema types

Every paginated field uses shared base types plus entity-specific types:

type PageInfo {
    hasNextPage: Boolean!
    hasPreviousPage: Boolean!
    startCursor: CursorKey
    endCursor: CursorKey
}

enum OrderDirection
    @goModel(model: "go.probo.inc/probo/pkg/page.OrderDirection") {
    ASC @goEnum(value: "go.probo.inc/probo/pkg/page.OrderDirectionAsc")
    DESC @goEnum(value: "go.probo.inc/probo/pkg/page.OrderDirectionDesc")
}

Each entity defines: enum XxxOrderField, input XxxOrder, type XxxConnection (with @goModel), type XxxEdge.

Connection fields on parent types use standard Relay arguments:

type Organization {
    vendors(
        first: Int
        after: CursorKey
        last: Int
        before: CursorKey
        orderBy: VendorOrder
        filter: VendorFilter
    ): VendorConnection!
}

Go connection type pattern

Each connection type lives in types/*_connection.go and follows this structure:

type (
    VendorOrderBy OrderBy[coredata.VendorOrderField]

    VendorConnection struct {
        TotalCount int
        Edges      []*VendorEdge
        PageInfo   PageInfo

        Resolver any
        ParentID gid.GID
    }
)

func NewVendorConnection(
    p *page.Page[*coredata.Vendor, coredata.VendorOrderField],
    parentType any,
    parentID gid.GID,
) *VendorConnection {
    edges := make([]*VendorEdge, len(p.Data))
    for i, v := range p.Data {
        edges[i] = NewVendorEdge(v, p.Cursor.OrderBy.Field)
    }

    return &VendorConnection{
        Edges:    edges,
        PageInfo: *NewPageInfo(p),

        Resolver: parentType,
        ParentID: parentID,
    }
}

func NewVendorEdge(
    v *coredata.Vendor,
    orderBy coredata.VendorOrderField,
) *VendorEdge {
    return &VendorEdge{
        Cursor: v.CursorKey(orderBy),
        Node:   NewVendor(v),
    }
}

Cursor format

Cursors are opaque CursorKey scalars. Internally they encode as base64url(JSON):

["<entity_global_id>", <sort_field_value>]

This enables keyset pagination — the database seeks directly to the right position instead of using OFFSET.

Keyset pagination

The database query uses the cursor to build a WHERE clause:

• DESC: rows where (field <= cursor_value) AND NOT (field = cursor_value AND id > cursor_id)
• ASC: rows where (field >= cursor_value) AND NOT (field = cursor_value AND id < cursor_id)

The query fetches size + 1 (or size + 2 with a cursor) rows to detect whether more pages exist. NewPage trims extra rows and sets hasNextPage / hasPreviousPage.

For backward pagination (last / before), SQL sort direction is reversed, then the result slice is reversed back.

Default page size is 25 when neither first nor last is provided.

Adding a new paginated field — checklist

1. Schema — add enum XxxOrderField (with @goModel/@goEnum), input XxxOrder, type XxxConnection (with @goModel and totalCount using @goField(forceResolver: true)), type XxxEdge, and the connection field with Relay arguments on the parent type
2. Coredata — add *_order_field.go (with Column(), IsValid(), marshaling), CursorKey(field) method on the entity, and the LoadAllBy* query using cursor SQL fragments + page.NewPage()
3. API types — add *_connection.go with OrderBy alias, connection struct, NewXxxConnection, NewXxxEdge
4. Resolver — implement the resolver (authorize, build order, build cursor, call service, build connection)
5. Codegen — run go generate for the relevant API package