feat(types): add json path type inference

src/select-query-parser/parser.ts

@@ -2,6 +2,7 @@
 // See https://github.com/PostgREST/postgrest/blob/2f91853cb1de18944a4556df09e52450b881cfb3/src/PostgREST/ApiRequest/QueryParams.hs#L282-L284
 
 import { SimplifyDeep } from '../types'
+import { JsonPathToAccessor } from './utils'
 
 /**
  * Parses a query.
@@ -220,13 +221,24 @@ type ParseNonEmbeddedResourceField<Input extends string> = ParseIdentifier<Input
 ]
   ? // Parse optional JSON path.
     (
-      Remainder extends `->${infer _}`
+      Remainder extends `->${infer PathAndRest}`
         ? ParseJsonAccessor<Remainder> extends [
             infer PropertyName,
             infer PropertyType,
             `${infer Remainder}`
           ]
-          ? [{ type: 'field'; name: Name; alias: PropertyName; castType: PropertyType }, Remainder]
+          ? [
+              {
+                type: 'field'
+                name: Name
+                alias: PropertyName
+                castType: PropertyType
+                jsonPath: JsonPathToAccessor<
+                  PathAndRest extends `${infer Path},${string}` ? Path : PathAndRest
+                >
+              },
+              Remainder
+            ]
           : ParseJsonAccessor<Remainder>
         : [{ type: 'field'; name: Name }, Remainder]
     ) extends infer Parsed
@@ -401,6 +413,7 @@ export namespace Ast {
     hint?: string
     innerJoin?: true
     castType?: string
+    jsonPath?: string
     aggregateFunction?: Token.AggregateFunction
     children?: Node[]
   }

src/select-query-parser/result.ts

@@ -15,6 +15,8 @@ import {
   GetFieldNodeResultName,
   IsAny,
   IsRelationNullable,
+  IsStringUnion,
+  JsonPathToType,
   ResolveRelationship,
   SelectQueryError,
 } from './utils'
@@ -239,6 +241,30 @@ type ProcessFieldNode<
   ? ProcessEmbeddedResource<Schema, Relationships, Field, RelationName>
   : ProcessSimpleField<Row, RelationName, Field>
 
+type ResolveJsonPathType<
+  Value,
+  Path extends string | undefined,
+  CastType extends PostgreSQLTypes
+> = Path extends string
+  ? JsonPathToType<Value, Path> extends never
+    ? // Always fallback if JsonPathToType returns never
+      TypeScriptTypes<CastType>
+    : JsonPathToType<Value, Path> extends infer PathResult
+    ? PathResult extends string
+      ? // Use the result if it's a string as we know that even with the string accessor ->> it's a valid type
+        PathResult
+      : IsStringUnion<PathResult> extends true
+      ? // Use the result if it's a union of strings
+        PathResult
+      : CastType extends 'json'
+      ? // If the type is not a string, ensure it was accessed with json accessor ->
+        PathResult
+      : // Otherwise it means non-string value accessed with string accessor ->> use the TypeScriptTypes result
+        TypeScriptTypes<CastType>
+    : TypeScriptTypes<CastType>
+  : // No json path, use regular type casting
+    TypeScriptTypes<CastType>
+
 /**
  * Processes a simple field (without embedded resources).
  *
@@ -261,8 +287,8 @@ type ProcessSimpleField<
       }
     : {
         // Aliases override the property name in the result
-        [K in GetFieldNodeResultName<Field>]: Field['castType'] extends PostgreSQLTypes // We apply the detected casted as the result type
-          ? TypeScriptTypes<Field['castType']>
+        [K in GetFieldNodeResultName<Field>]: Field['castType'] extends PostgreSQLTypes
+          ? ResolveJsonPathType<Row[Field['name']], Field['jsonPath'], Field['castType']>
           : Row[Field['name']]
       }
   : SelectQueryError<`column '${Field['name']}' does not exist on '${RelationName}'.`>

src/select-query-parser/utils.ts

@@ -544,3 +544,37 @@ export type FindFieldMatchingRelationships<
       name: Field['name']
     }
   : SelectQueryError<'Failed to find matching relation via name'>
+
+export type JsonPathToAccessor<Path extends string> = Path extends `${infer P1}->${infer P2}`
+  ? P2 extends `>${infer Rest}` // Handle ->> operator
+    ? JsonPathToAccessor<`${P1}.${Rest}`>
+    : P2 extends string // Handle -> operator
+    ? JsonPathToAccessor<`${P1}.${P2}`>
+    : Path
+  : Path extends `>${infer Rest}` // Clean up any remaining > characters
+  ? JsonPathToAccessor<Rest>
+  : Path extends `${infer P1}::${infer _}` // Handle type casting
+  ? JsonPathToAccessor<P1>
+  : Path extends `${infer P1}${')' | ','}${infer _}` // Handle closing parenthesis and comma
+  ? P1
+  : Path
+
+export type JsonPathToType<T, Path extends string> = Path extends ''
+  ? T
+  : ContainsNull<T> extends true
+  ? JsonPathToType<Exclude<T, null>, Path>
+  : Path extends `${infer Key}.${infer Rest}`
+  ? Key extends keyof T
+    ? JsonPathToType<T[Key], Rest>
+    : never
+  : Path extends keyof T
+  ? T[Path]
+  : never
+
+export type IsStringUnion<T> = string extends T
+  ? false
+  : T extends string
+  ? [T] extends [never]
+    ? false
+    : true
+  : false

test/basic.ts

@@ -1,5 +1,5 @@
 import { PostgrestClient } from '../src/index'
-import { Database } from './types'
+import { CustomUserDataType, Database } from './types'
 
 const REST_URL = 'http://localhost:3000'
 const postgrest = new PostgrestClient<Database>(REST_URL)
@@ -1693,7 +1693,10 @@ test('select with no match', async () => {
 })
 
 test('update with no match - return=minimal', async () => {
-  const res = await postgrest.from('users').update({ data: '' }).eq('username', 'missing')
+  const res = await postgrest
+    .from('users')
+    .update({ data: '' as unknown as CustomUserDataType })
+    .eq('username', 'missing')
   expect(res).toMatchInlineSnapshot(`
     Object {
       "count": null,
@@ -1706,7 +1709,11 @@ test('update with no match - return=minimal', async () => {
 })
 
 test('update with no match - return=representation', async () => {
-  const res = await postgrest.from('users').update({ data: '' }).eq('username', 'missing').select()
+  const res = await postgrest
+    .from('users')
+    .update({ data: '' as unknown as CustomUserDataType })
+    .eq('username', 'missing')
+    .select()
   expect(res).toMatchInlineSnapshot(`
     Object {
       "count": null,