> For the complete documentation index, see [llms.txt](https://docs.opensoutheners.com/oss/llms.txt). Markdown versions of documentation pages are available by appending `.md` to page URLs; this page is available as [Markdown](https://docs.opensoutheners.com/oss/flex-url/advanced/typed-schemas.md).

# Typed Schemas (TypeScript)

Narrow the TypeScript builder to a specific endpoint's allowed filters, sorts, includes, fields, and appends at compile time.

{% hint style="info" %}
This is a TypeScript-only feature. PHP has no compile-time generics, so `FlexUrl::make()`/`::from()` accept only a `$url` and `FlexUrlOptions` — there is no schema-narrowing equivalent on that side.
{% endhint %}

`flexUrl<S extends EndpointSchema>(path, schema?)` narrows `filter()`/`sort()`/`include()`/ `fields()`/`append()` arguments to a specific endpoint's allowed vocabulary at compile time. `EndpointSchema` is the shared contract generated by apiable's `apiable:types` exporter, so the schema doesn't need to be hand-written in most projects.

```ts
import {flexUrl, type EndpointSchema} from 'flex-url';

interface IssuesSchema extends EndpointSchema {
  resource: 'issues';
  path: '/api/v1/issues';
  filters: {
    status: {operators: ['equal']; values: ['open', 'closed']};
    due_at: {operators: ['gte', 'lte']};
  };
  sorts: ['priority', 'due_at'];
  includes: ['project', 'assignee'];
  fields: {issues: ['title', 'status', 'priority']};
  appends: {issues: ['is_overdue']};
}

// S is inferred from the `schema` argument — no explicit generic needed.
const issues = flexUrl('/api/v1/issues', issuesSchema);

issues.filter('status', 'open');   // OK
issues.filter('budget', '100');    // compile error: "budget" isn't in IssuesSchema['filters']

// Or narrow with an explicit generic and no runtime schema object:
const alsoIssues = flexUrl<IssuesSchema>('/api/v1/issues');
```

## What gets narrowed

| Call                                      | Narrowed to                                                 |
| ----------------------------------------- | ----------------------------------------------------------- |
| `filter(attribute, ...)`                  | `keyof schema.filters`                                      |
| `filter(attribute, operator, value)`      | that attribute's registered operators (plus the `eq` alias) |
| `sort(attribute)` / `sortDesc(attribute)` | `schema.sorts[number]`                                      |
| `include(...relationships)`               | `schema.includes[number]`                                   |
| `fields(type, ...columns)`                | `keyof schema.fields`, then that type's columns             |
| `append(type, ...accessors)`              | `keyof schema.appends`, then that type's accessors          |

A schema's `scope`-operator filters are excluded from the narrowed operator union for `filter()` — use [`filterScope()`](/oss/flex-url/building-urls/filters.md#scoped-filters) for those, which isn't schema-narrowed.

## Dev-mode diagnostics

Passing a **runtime** `schema` object (not just the generic) additionally enables dev-mode diagnostics: an unrecognised filter/sort/include/fields/appends call logs a `console.warn` — it never throws or changes behaviour — useful for catching a typo that an untyped call site wouldn't catch at compile time (e.g. a value read from user input, or a dynamically-built attribute name).

Omit the schema argument (explicit-generic-only usage, `flexUrl<IssuesSchema>(path)`) to skip these warnings entirely — there's no runtime object to check against.

## No schema at all

`flexUrl(path)` with no schema argument and no explicit generic accepts any `string` for every attribute/type/operator argument — the unnarrowed, `EndpointSchema | undefined = undefined` default. This is the same builder used throughout the rest of these docs.


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