chore: 12x faster TypeScript type-checking across the monorepo (#16796)

TypeScript was very slow in this repo - worst when editing files in
`test/`, and for ESLint (which runs TypeScript). This PR makes it a lot
faster with a few small, type-only changes.

## Why it was slow

Two simple root causes:

1. **A few core field helpers and config types made TypeScript build
huge piles of throwaway types** over and over. The `Field` config types
are big and self-referencing, and these helpers/types kept rebuilding
them. A handful of one-line type changes stop that.
2. **Every test folder loaded the entire `test/` folder instead of its
own files.** Each `test/<suite>/tsconfig.json` only said `extends`,
which made it pull in all ~1,600 test files (plus 87 clashing type
declarations) every time you opened one test file.

## What changed (4 small fixes)

1. **Field helper functions** (`fieldAffectsData` and ~8 siblings, used
in 100+ places): they narrowed a type by _combining_ it with a big list
of field types, which made TypeScript build hundreds of throwaway types
on every call. Changed them to _pick_ from the types that already exist
instead. Same result, almost no new types created.
2. **Dashboard widgets type**: the sanitized config ran the whole (big,
recursive) field type through the DeepRequired helper, rebuilding it
from scratch.
3. **Import-map helper (`hasKey`)**: same "combine with a big type"
problem. Removed it (callers didn't need it and it's internal-only)
4. **Test folder tsconfigs**: gave each `test/<suite>/tsconfig.json` its
own file list so it only loads its own folder, not all of `test/`.

## Benchmarks

### Per package (`tsc --noEmit`, each package's own code)

```
pnpm exec tsc -b packages/payload && pnpm exec tsc -p packages/payload/tsconfig.json --noEmit --extendedDiagnostics
```

| Package | Before | After | Faster | Types before → after |
| ---------------- | ------ | --------- | -------- |
-------------------- |
| **next** | 62.7 s | **5.1 s** | **~12×** | 186,227 → 69,716 |
| **payload** | 44.0 s | **5.1 s** | **~9×** | 492,198 → 110,403 |
| **ui** | 28.7 s | **7.1 s** | **~4×** | 187,494 → 104,349 |
| db-mongodb | 3.2 s | 1.8 s | ~1.8× | 69,486 → 68,060 |
| drizzle | 2.3 s | 1.6 s | ~1.4× | 127,890 → 126,040 |
| richtext-lexical | 3.6 s | 3.3 s | ~same | 74,602 → 73,993 |
| db-postgres | 0.29 s | 0.29 s | same | 24,461 → 24,461 |
| translations | 0.33 s | 0.30 s | same | 51,282 → 51,282 |

The big wins (payload, next, ui) are the packages that use the field
types heavily.

### Whole monorepo build

```
pnpm bf
```

| | Before | After |
| ------------------ | ----------------------------------------------- |
------------------ |
| Full build | 2m27 | **47s** |

### Test packages

| | Before | After |
| ----------------------------------------------- |
---------------------------------- | --------------------------------- |
| `test/fields` suite | Ran out of memory | **20.0 s** |
| Single test file that imports `payload` | **76.6 s**, 4.25 GB, 489,838
types | **4.6 s**, 0.62 GB, 113,079 types |

Single-file: **~17× faster, ~7× less memory, ~4× fewer types.**

### Editor latency (real `tsserver` - open a file, time until errors
show)

| Open this file | Before (load / errors) | After (load / errors) |
| ---------------------------------------------- |
---------------------- | --------------------- |
| **a `test/` file** (`test/fields/int.spec.ts`) | 13.7 s / **14.0 s** |
2.6 s / **2.5 s** |
| a `payload` source file (`config/client.ts`) | 1.5 s / 3.1 s | 1.2 s /
1.4 s |

Author: AlessioGr

packages/next/src/views/Dashboard/Default/ModularDashboard/index.tsx

@@ -30,7 +30,7 @@ export async function ModularDashboard(props: DashboardViewServerProps) {
     const widgetSlug = layoutItem.id.slice(0, layoutItem.id.lastIndexOf('-'))
     const widgetConfig = widgets.find((widget) => widget.slug === widgetSlug)
     const widgetData = widgetConfig?.fields?.length
-      ? extractLocaleData(layoutItem.data || {}, req.locale || 'en', widgetConfig.fields as Field[])
+      ? extractLocaleData(layoutItem.data || {}, req.locale || 'en', widgetConfig.fields)
       : layoutItem.data || {}
 
     return {

packages/next/src/views/Dashboard/Default/ModularDashboard/renderWidget/renderWidgetServerFn.ts

@@ -59,7 +59,7 @@ export const renderWidgetHandler: ServerFunction<
 
   try {
     const localeFilteredData = widgetConfig.fields?.length
-      ? extractLocaleData(widgetData || {}, req.locale || 'en', widgetConfig.fields as Field[])
+      ? extractLocaleData(widgetData || {}, req.locale || 'en', widgetConfig.fields)
       : widgetData || {}
 
     const serverProps: WidgetServerProps = {

packages/payload/src/bin/generateImportMap/iterateFields.ts

@@ -3,10 +3,13 @@ import type { PayloadComponent, SanitizedConfig } from '../../config/types.js'
 import type { Block, Field, Tab } from '../../fields/config/types.js'
 import type { AddToImportMap, Imports, InternalImportMap } from './index.js'
 
-function hasKey<T, K extends string>(
-  obj: null | T | undefined,
+// Only checks that `obj` has `key`.
+// Keep this narrow: adding `& T` makes TypeScript expand large field types at every call,
+// and callers already read components from `field` directly and don't need extra type info from this function.
+function hasKey<K extends string>(
+  obj: unknown,
   key: K,
-): obj is { [P in K]: PayloadComponent | PayloadComponent[] } & T {
+): obj is { [P in K]: PayloadComponent | PayloadComponent[] } {
   return obj != null && Object.prototype.hasOwnProperty.call(obj, key)
 }
 

packages/payload/src/config/types.ts

@@ -1623,8 +1623,16 @@ export type Config = {
  */
 export type SanitizedConfig = {
   admin: {
+    /**
+     * `Required` (shallow) marks the top-level dashboard props as required, mainly `defaultLayout`,
+     * which sanitizing always fills in. Do not switch this to the `DeepRequired` used below: it
+     * recurses into the widgets and re-expands the whole `Field` type (a large self-referencing
+     * union), which is very expensive to check. Never run a `Field`-bearing type through
+     * `DeepRequired`.
+     */
+    dashboard: Required<NonNullable<NonNullable<Config['admin']>['dashboard']>>
     timezones: SanitizedTimezoneConfig
-  } & DeepRequired<Config['admin']>
+  } & DeepRequired<Omit<NonNullable<Config['admin']>, 'dashboard'>>
   blocks?: FlattenedBlock[]
   collections: SanitizedCollectionConfig[]
   /** Default richtext editor to use for richText fields */

packages/payload/src/fields/config/types.ts

@@ -1951,7 +1951,7 @@ export type FieldWithMaxDepthClient = JoinFieldClient | RelationshipFieldClient
 
 export function fieldHasSubFields<TField extends ClientField | Field | TabAsField>(
   field: TField,
-): field is TField & (TField extends ClientField ? FieldWithSubFieldsClient : FieldWithSubFields) {
+): field is Extract<TField, FieldWithSubFields | FieldWithSubFieldsClient> {
   return (
     field.type === 'group' ||
     field.type === 'array' ||
@@ -1962,19 +1962,19 @@ export function fieldHasSubFields<TField extends ClientField | Field | TabAsFiel
 
 export function fieldIsArrayType<TField extends ClientField | Field>(
   field: TField,
-): field is TField & (TField extends ClientField ? ArrayFieldClient : ArrayField) {
+): field is Extract<TField, ArrayField | ArrayFieldClient> {
   return field.type === 'array'
 }
 
 export function fieldIsBlockType<TField extends ClientField | Field>(
   field: TField,
-): field is TField & (TField extends ClientField ? BlocksFieldClient : BlocksField) {
+): field is Extract<TField, BlocksField | BlocksFieldClient> {
   return field.type === 'blocks'
 }
 
 export function fieldIsGroupType<TField extends ClientField | Field>(
   field: TField,
-): field is TField & (TField extends ClientField ? GroupFieldClient : GroupField) {
+): field is Extract<TField, GroupField | GroupFieldClient> {
   return field.type === 'group'
 }
 
@@ -1992,13 +1992,13 @@ export function optionIsValue(option: Option): option is string {
 
 export function fieldSupportsMany<TField extends ClientField | Field>(
   field: TField,
-): field is TField & (TField extends ClientField ? FieldWithManyClient : FieldWithMany) {
+): field is Extract<TField, FieldWithMany | FieldWithManyClient> {
   return field.type === 'select' || field.type === 'relationship' || field.type === 'upload'
 }
 
 export function fieldHasMaxDepth<TField extends ClientField | Field>(
   field: TField,
-): field is TField & (TField extends ClientField ? FieldWithMaxDepthClient : FieldWithMaxDepth) {
+): field is Extract<TField, FieldWithMaxDepth | FieldWithMaxDepthClient> {
   return (
     (field.type === 'upload' || field.type === 'relationship' || field.type === 'join') &&
     typeof field.maxDepth === 'number'
@@ -2007,9 +2007,7 @@ export function fieldHasMaxDepth<TField extends ClientField | Field>(
 
 export function fieldIsPresentationalOnly<
   TField extends ClientField | Field | TabAsField | TabAsFieldClient,
->(
-  field: TField,
-): field is TField & (TField extends ClientField | TabAsFieldClient ? UIFieldClient : UIField) {
+>(field: TField): field is Extract<TField, UIField | UIFieldClient> {
   return field.type === 'ui'
 }
 
@@ -2045,8 +2043,10 @@ export function fieldAffectsData<
   TField extends ClientField | Field | TabAsField | TabAsFieldClient,
 >(
   field: TField,
-): field is TField &
-  (TField extends ClientField | TabAsFieldClient ? FieldAffectingDataClient : FieldAffectingData) {
+  // Narrows to field types that hold data (`name` fields). `Extract` keeps the
+  // existing `TField` members instead of creating intersections. Avoid `TField & (...)`
+  // here: with the large recursive `Field` union, it is much slower to typecheck.
+): field is Extract<TField, FieldAffectingData | FieldAffectingDataClient> {
   return 'name' in field && !fieldIsPresentationalOnly(field)
 }
 

packages/ui/src/utilities/buildFieldSchemaMap/index.ts

@@ -83,7 +83,7 @@ export const buildFieldSchemaMap = (args: {
     const matchedWidget = config.admin?.dashboard?.widgets?.find(
       (widget) => widget.slug === widgetSlug,
     )
-    const widgetFields = matchedWidget?.fields as Field[] | undefined
+    const widgetFields = matchedWidget?.fields
 
     if (widgetFields?.length) {
       schemaMap.set(widgetSlug, {

test/_community/tsconfig.json

@@ -1,3 +1,4 @@
 {
   "extends": "../tsconfig.json",
+  "include": ["./**/*.ts", "./**/*.tsx"]
 }

test/a11y/tsconfig.json

@@ -1,3 +1,4 @@
 {
-  "extends": "../tsconfig.json"
+  "extends": "../tsconfig.json",
+  "include": ["./**/*.ts", "./**/*.tsx"]
 }

test/access-control/tsconfig.json

@@ -1,3 +1,4 @@
 {
-  "extends": "../tsconfig.json"
+  "extends": "../tsconfig.json",
+  "include": ["./**/*.ts", "./**/*.tsx"]
 }

test/admin/tsconfig.json

@@ -1,3 +1,4 @@
 {
-  "extends": "../tsconfig.json"
+  "extends": "../tsconfig.json",
+  "include": ["./**/*.ts", "./**/*.tsx"]
 }