Infer input types from json_populate_recordset and friends (#14)

* initial implementation to infer input types from json_populate_recordset and friends

* make json_populate_record detection more robust

* handle JSON.t stringification properly so arrays can be handled

* add another example + fix types

* generated

Author: zth

CHANGELOG.md

@@ -1,8 +1,10 @@
 # main
 
+- Make sure `JSON.t` is properly stringified so JSON arrays can be passed to params expecting `JSON.t` without them being confused for regular Postgres arrays.
 - Auto-escape all ReScript keywords in generated record field names.
 - Add automatic parsing of PostgreSQL check constraints to generate ReScript polyvariant types for enumeration-style constraints. Supports both `column IN (value1, value2, ...)` and `column = ANY (ARRAY[value1, value2, ...])` patterns with string and integer values.
 - Add top-level literal inference for SELECT queries. When a query returns literal values with aliases (e.g., `SELECT 'success' as status, 42 as code`), PgTyped now automatically infers specific polyvariant types like `[#"success"]` and `[#42]` instead of generic `string` and `int` types. This provides better type safety and autocompletion. Also works with UNION queries where literals are consistent across all branches.
+- Add support for PostgreSQL JSON population functions (`json_populate_record`, `json_populate_recordset`, `jsonb_populate_record`, `jsonb_populate_recordset`, `json_to_record`, `jsonb_to_recordset`). This supports efficient bulk operations.
 - Remove dependency on `@rescript/core` since it's not really used.
 
 # 2.6.0

RESCRIPT.md

@@ -170,6 +170,75 @@ let books = await client->GetBooksByStatus.many({
 
 This feature works seamlessly with both separate SQL files and SQL-in-ReScript modes.
 
+## JSON Population Functions
+
+`pgtyped-rescript` provides support for PostgreSQL's JSON population functions, enabling type-safe conversion between JSON data and database records.
+
+### Supported Functions
+
+- **`json_populate_record`** - Converts a JSON object to a PostgreSQL record
+- **`json_populate_recordset`** - Converts a JSON array to a set of PostgreSQL records
+- **`jsonb_populate_record`** - Binary JSON variant of `json_populate_record`
+- **`jsonb_populate_recordset`** - Binary JSON variant of `json_populate_recordset`
+- **`json_to_record`** - Converts JSON to a record with explicit column definitions
+- **`jsonb_to_recordset`** - Converts JSONB array to records with explicit column definitions
+
+### Usage Examples
+
+**Bulk insert with `json_populate_recordset`:**
+
+```sql
+/* @name bulkInsertBooks */
+INSERT INTO books (name, author_id, categories, rank)
+SELECT
+  event.name,
+  event.author_id,
+  event.categories,
+  event.rank
+FROM json_populate_recordset(null::books, :books!) as event
+RETURNING *;
+```
+
+**Update single record with `json_populate_record`:**
+
+```sql
+/* @name updateBookFromJson */
+UPDATE books
+SET (name, author_id, categories, rank) = (
+  SELECT
+    r.name,
+    r.author_id,
+    r.categories,
+    r.rank
+  FROM json_populate_record(null::books, :bookData!) as r
+)
+WHERE id = :bookId!
+RETURNING *;
+```
+
+**Example:**
+
+```rescript
+let bulkInsert = %sql.many(`
+  INSERT INTO books (name, author_id, categories, rank)
+  SELECT
+    event.name,
+    event.author_id,
+    event.categories,
+    event.rank
+  FROM json_populate_recordset(null::books, :books!) as event
+  RETURNING *
+`)
+
+// Usage with full type safety
+let newBooks = await client->bulkInsert({
+  books: [
+    {name: "Book 1", author_id: 1, categories: ["fiction"], rank: 1},
+    {name: "Book 2", author_id: 2, categories: ["sci-fi"], rank: 2}
+  ]
+})
+```
+
 ## Literal Type Inference
 
 `pgtyped-rescript` automatically infers specific polyvariant types for literal values in your SQL queries, providing enhanced type safety and better development experience.