## Why Two DAP Impact v1 panels need a field-function parameter that takes several values: - `userTier(thresholds=[4, 25, 100])` on DuoWorkflows (#209) - the engine requires `thresholds: [Int!]` (no default, at most 9 values, strictly ascending positive integers) and the dashboard pre-scales them per selected period (https://gitlab.com/gitlab-org/gitlab/-/work_items/627697), so the values must travel in the query - `totalCount(status=["paused", "input_required"])` on DuoWorkflows - the engine's `totalCount(status: [String!])`, needed to show several session statuses as aliased metrics in one query (Work tab) Today `ParameterConstraint` (`src/types/field_parameter.rs`) only knows `Enum` (one string) and `Range` (one float), `function_arg_value` (`src/parser/fields.rs`) only parses a quoted string, float, int or identifier, `FunctionArg` values and the resolved `(key, value)` parameters are plain `String`s, and `format_graphql_params` (`src/codegen/graphql.rs`) only renders quoted-vs-bare scalars. ## What - A list-valued parameter kind: `ParameterConstraint::List { item: Enum | IntRange, min_len, max_len }` (or equivalent), list defaults in `ParameterValue`, list rendering in codegen (`thresholds: [4, 25, 100]`, `status: ["paused"]`) - List literal syntax in field-function arguments: `name(key=[v1, v2, ...])`, items being the existing scalar values - Scalar sugar: a single scalar for a list-kind parameter compiles to a one-element list (`totalCount(status="paused")`) - A rule for list parameters the engine gives no default for: `FieldParameterDef::new` requires a default matching the constraint and bare parameterisable fields are resolved with defaults filled in (`resolve_static_field` in `src/analyzer/analytics.rs`). `status` is optional on the engine side (an empty list means no filter), `thresholds` is required (the engine rejects a bare `userTier`), so GLQL needs an empty-list default for `status` and either a GLQL-side default or a "parameter required" error for `userTier` without `thresholds` - Sort parameter emission carries the list (`parameters: { thresholds: [4, 25, 100] }`) - Alias slugs for parameterised fields stay valid GraphQL names with list values, and distinct lists get distinct slugs (`sanitize_slug_value` maps `[`, `]`, `,` and spaces all to `_x`, so the slug has to come from the item list, not the raw literal) - Schema builder + `src/schema/schema.json` describe the list kind so the Data Analyst agent learns it (`schema.json` already uses `kind: List` with a nested item kind for filter field types, so the parameter shape can mirror it) - Parameterised-field labels have a sensible form for lists ## Notes - Brackets rather than the parenthesised form GLQL filters use for `in (...)`: inside a call, `(...)` would be ambiguous with nested functions. `[` is not used anywhere in the grammar today - Language change (parser + grammar docs), so this is an L item in the DAP Impact sizing - The compiler already accepts the same base metric several times when each instance has a unique alias, so `totalCount as "created", totalCount(status="paused") as "paused"` needs nothing beyond this issue - as long as a bare `totalCount` keeps resolving to a `ParameterizedField` (with the empty-list default) so it gets a slug; `check_duplicate_base` in `src/analyzer/resolved_fields.rs` rejects the pair when any instance has no slug - The engine has no generic list-length rule: `ParameterizedDefinition#validate_parameters` only checks `in:` membership, and the required / at-most-9 / ascending checks are `TierDimension`-specific. `min_len` and `max_len` are therefore per-parameter GLQL-side mirrors of those rules; the ascending-order check stays with the engine unless GLQL adds it - #187 also adds `ParameterConstraint` / `ParameterValue` variants (the `Xd` pattern and a datetime `origin`) and touches the same `validate_param_values`, `format_graphql_params`, schema builder and `schema.json` code paths. No contradiction between the two, but whichever lands second rebases the match arms, so coordinate the kind names ## References - #209 (userTier, flowTypesUsed, activeDays) - blocked by this - #207 (status filter + dimension) - the `totalCount(status=...)` metric follows this - Work tab thread: https://gitlab.com/groups/gitlab-org/-/work_items/23421#note_3831450220 - Tracking: #188