Infer top level literals

CHANGELOG.md

@@ -2,6 +2,7 @@
 
 - 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.
 - Remove dependency on `@rescript/core` since it's not really used.
 
 # 2.6.0

RESCRIPT.md

@@ -170,6 +170,78 @@ let books = await client->GetBooksByStatus.many({
 
 This feature works seamlessly with both separate SQL files and SQL-in-ReScript modes.
 
+## 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.
+
+### How It Works
+
+When your SQL queries return literal values with aliases, `pgtyped-rescript` generates specific polyvariant types instead of generic `string`, `int`, etc. This works for both simple SELECT queries and UNION queries where literals are consistent across all branches.
+
+### Examples
+
+**Simple literals:**
+
+```sql
+/* @name getStatus */
+SELECT
+  'success' as status,
+  200 as code,
+  'active' as state
+```
+
+Generated ReScript type:
+
+```rescript
+type getStatusResult = {
+  status: [#"success"],
+  code: [#200],
+  state: [#"active"],
+}
+```
+
+**Union queries with consistent literals:**
+
+```sql
+/* @name getDocumentStatus */
+SELECT 'draft' as status, 1 as version
+UNION ALL
+SELECT 'published' as status, 2 as version
+```
+
+Generated ReScript type:
+
+```rescript
+type getDocumentStatusResult = {
+  status: [#"draft" | #"published"],
+  version: [#1 | #2],
+}
+```
+
+**SQL-in-ReScript example:**
+
+```rescript
+let getOrderStatus = %sql.many(`
+  SELECT
+    'pending' as status,
+    0 as priority
+  UNION ALL
+  SELECT
+    'shipped' as status,
+    1 as priority
+`)
+
+// Returns: array<{status: [#"pending" | #"shipped"], priority: [#0 | #1]}>
+let statuses = await client->getOrderStatus()
+```
+
+### Smart Inference Rules
+
+- **Consistent literals**: Only infers polyvariants when all literal values for the same alias are actual literals (not expressions)
+- **Context-aware**: Handles nested queries correctly, only inferring from the top-level SELECT
+- **Duplicate handling**: Automatically deduplicates identical literals in UNION queries
+- **Mixed expressions**: Falls back to generic types when mixing literals with expressions (e.g., `'draft' || 'suffix'`)
+
 ## API
 
 ### `PgTyped`

packages/cli/src/generator.ts

@@ -100,7 +100,7 @@ export async function queryToTypeDeclarations(
   if (typeError || hasAnonymousColumns) {
     // tslint:disable:no-console
     if (typeError) {
-      console.error('Error in query. Details: %o', typeData);
+      console.error(`Error in query "${queryName}". Details: %o`, typeData);
       if (config.failOnError) {
         throw new Error(
           `Query "${queryName}" is invalid. Can't generate types.`,
@@ -147,8 +147,6 @@ export async function queryToTypeDeclarations(
                 return `#"${v.value}"`;
               case 'integer':
                 return `#${v.value}`;
-              case 'float':
-                return `#${v.value}`;
             }
           })
           .join(' | ')}]`;

packages/cli/src/parseRescript.ts

@@ -28,8 +28,6 @@ export function parseCode(
       .toString(),
   );
 
-  content.reverse();
-
   const queries: Array<string> = [];
   let unnamedQueriesCount = 0;
 

packages/cli/src/res/PgTyped.res

@@ -124,7 +124,12 @@ module Pg = {
 }
 
 module IR = {
-  type t
+  type t = private {
+    queryName: option<string>,
+    statement: string,
+    usedParamSet: dict<bool>,
+    params: array<Js.Json.t>, // This can be more thoroughly typed if wanted
+  }
 }
 
 module PreparedStatement = {

packages/example/src/books/BookServiceParams2__sql.res

@@ -28,7 +28,7 @@ type query1Query = {
   result: query1Result,
 }
 
-%%private(let query1IR: IR.t = %raw(`{"usedParamSet":{"notification":true},"params":[{"name":"notification","required":false,"transform":{"type":"pick_tuple","keys":[{"name":"payload","required":false},{"name":"user_id","required":false},{"name":"type","required":false}]},"locs":[{"a":58,"b":70}]}],"statement":"INSERT INTO notifications (payload, user_id, type) VALUES :notification"}`))
+%%private(let query1IR: IR.t = %raw(`{"queryName":"Query1","usedParamSet":{"notification":true},"params":[{"name":"notification","required":false,"transform":{"type":"pick_tuple","keys":[{"name":"payload","required":false},{"name":"user_id","required":false},{"name":"type","required":false}]},"locs":[{"a":58,"b":70}]}],"statement":"INSERT INTO notifications (payload, user_id, type) VALUES :notification"}`))
 
 /**
  Runnable query:

packages/example/src/books/BookServiceParams__sql.res

@@ -28,7 +28,7 @@ type query1Query = {
   result: query1Result,
 }
 
-%%private(let query1IR: IR.t = %raw(`{"usedParamSet":{"notification":true},"params":[{"name":"notification","required":false,"transform":{"type":"pick_tuple","keys":[{"name":"payload","required":false},{"name":"user_id","required":false},{"name":"type","required":false}]},"locs":[{"a":58,"b":70}]}],"statement":"INSERT INTO notifications (payload, user_id, type) VALUES :notification"}`))
+%%private(let query1IR: IR.t = %raw(`{"queryName":"Query1","usedParamSet":{"notification":true},"params":[{"name":"notification","required":false,"transform":{"type":"pick_tuple","keys":[{"name":"payload","required":false},{"name":"user_id","required":false},{"name":"type","required":false}]},"locs":[{"a":58,"b":70}]}],"statement":"INSERT INTO notifications (payload, user_id, type) VALUES :notification"}`))
 
 /**
  Runnable query:

packages/example/src/books/BookService__sql.gen.tsx

@@ -11,63 +11,63 @@ export type category = "novel" | "science-fiction" | "thriller";
 
 export type categoryArray = category[];
 
-/** 'BooksByAuthor' parameters type */
-export type booksByAuthorParams = { readonly authorName: string };
+/** 'FindBookById' parameters type */
+export type findBookByIdParams = { readonly id?: number };
 
-/** 'BooksByAuthor' return type */
-export type booksByAuthorResult = {
+/** 'FindBookById' return type */
+export type findBookByIdResult = {
   readonly author_id: (undefined | number); 
   readonly categories: (undefined | categoryArray); 
   readonly id: number; 
   readonly name: (undefined | string); 
   readonly rank: (undefined | number)
 };
 
-/** 'BooksByAuthor' query type */
-export type booksByAuthorQuery = { readonly params: booksByAuthorParams; readonly result: booksByAuthorResult };
+/** 'FindBookById' query type */
+export type findBookByIdQuery = { readonly params: findBookByIdParams; readonly result: findBookByIdResult };
 
-/** 'FindBookById' parameters type */
-export type findBookByIdParams = { readonly id?: number };
+/** 'BooksByAuthor' parameters type */
+export type booksByAuthorParams = { readonly authorName: string };
 
-/** 'FindBookById' return type */
-export type findBookByIdResult = {
+/** 'BooksByAuthor' return type */
+export type booksByAuthorResult = {
   readonly author_id: (undefined | number); 
   readonly categories: (undefined | categoryArray); 
   readonly id: number; 
   readonly name: (undefined | string); 
   readonly rank: (undefined | number)
 };
 
-/** 'FindBookById' query type */
-export type findBookByIdQuery = { readonly params: findBookByIdParams; readonly result: findBookByIdResult };
+/** 'BooksByAuthor' query type */
+export type booksByAuthorQuery = { readonly params: booksByAuthorParams; readonly result: booksByAuthorResult };
 
 /** Returns an array of all matched results. */
-export const BooksByAuthor_many: (_1:PgTyped_Pg_Client_t, _2:booksByAuthorParams) => Promise<booksByAuthorResult[]> = BookService__sqlJS.BooksByAuthor.many as any;
+export const FindBookById_many: (_1:PgTyped_Pg_Client_t, _2:findBookByIdParams) => Promise<findBookByIdResult[]> = BookService__sqlJS.FindBookById.many as any;
 
 /** Returns exactly 1 result. Returns `None` if more or less than exactly 1 result is returned. */
-export const BooksByAuthor_one: (_1:PgTyped_Pg_Client_t, _2:booksByAuthorParams) => Promise<(undefined | booksByAuthorResult)> = BookService__sqlJS.BooksByAuthor.one as any;
+export const FindBookById_one: (_1:PgTyped_Pg_Client_t, _2:findBookByIdParams) => Promise<(undefined | findBookByIdResult)> = BookService__sqlJS.FindBookById.one as any;
 
 /** Returns exactly 1 result. Raises `Exn.t` (with an optionally provided `errorMessage`) if more or less than exactly 1 result is returned. */
-export const BooksByAuthor_expectOne: (_1:PgTyped_Pg_Client_t, _2:booksByAuthorParams, errorMessage:(undefined | string)) => Promise<booksByAuthorResult> = BookService__sqlJS.BooksByAuthor.expectOne as any;
+export const FindBookById_expectOne: (_1:PgTyped_Pg_Client_t, _2:findBookByIdParams, errorMessage:(undefined | string)) => Promise<findBookByIdResult> = BookService__sqlJS.FindBookById.expectOne as any;
 
 /** Executes the query, but ignores whatever is returned by it. */
-export const BooksByAuthor_execute: (_1:PgTyped_Pg_Client_t, _2:booksByAuthorParams) => Promise<void> = BookService__sqlJS.BooksByAuthor.execute as any;
+export const FindBookById_execute: (_1:PgTyped_Pg_Client_t, _2:findBookByIdParams) => Promise<void> = BookService__sqlJS.FindBookById.execute as any;
 
-export const booksByAuthor: (params:booksByAuthorParams, client:PgTyped_Pg_Client_t) => Promise<booksByAuthorResult[]> = BookService__sqlJS.booksByAuthor as any;
+export const findBookById: (params:findBookByIdParams, client:PgTyped_Pg_Client_t) => Promise<findBookByIdResult[]> = BookService__sqlJS.findBookById as any;
 
 /** Returns an array of all matched results. */
-export const FindBookById_many: (_1:PgTyped_Pg_Client_t, _2:findBookByIdParams) => Promise<findBookByIdResult[]> = BookService__sqlJS.FindBookById.many as any;
+export const BooksByAuthor_many: (_1:PgTyped_Pg_Client_t, _2:booksByAuthorParams) => Promise<booksByAuthorResult[]> = BookService__sqlJS.BooksByAuthor.many as any;
 
 /** Returns exactly 1 result. Returns `None` if more or less than exactly 1 result is returned. */
-export const FindBookById_one: (_1:PgTyped_Pg_Client_t, _2:findBookByIdParams) => Promise<(undefined | findBookByIdResult)> = BookService__sqlJS.FindBookById.one as any;
+export const BooksByAuthor_one: (_1:PgTyped_Pg_Client_t, _2:booksByAuthorParams) => Promise<(undefined | booksByAuthorResult)> = BookService__sqlJS.BooksByAuthor.one as any;
 
 /** Returns exactly 1 result. Raises `Exn.t` (with an optionally provided `errorMessage`) if more or less than exactly 1 result is returned. */
-export const FindBookById_expectOne: (_1:PgTyped_Pg_Client_t, _2:findBookByIdParams, errorMessage:(undefined | string)) => Promise<findBookByIdResult> = BookService__sqlJS.FindBookById.expectOne as any;
+export const BooksByAuthor_expectOne: (_1:PgTyped_Pg_Client_t, _2:booksByAuthorParams, errorMessage:(undefined | string)) => Promise<booksByAuthorResult> = BookService__sqlJS.BooksByAuthor.expectOne as any;
 
 /** Executes the query, but ignores whatever is returned by it. */
-export const FindBookById_execute: (_1:PgTyped_Pg_Client_t, _2:findBookByIdParams) => Promise<void> = BookService__sqlJS.FindBookById.execute as any;
+export const BooksByAuthor_execute: (_1:PgTyped_Pg_Client_t, _2:booksByAuthorParams) => Promise<void> = BookService__sqlJS.BooksByAuthor.execute as any;
 
-export const findBookById: (params:findBookByIdParams, client:PgTyped_Pg_Client_t) => Promise<findBookByIdResult[]> = BookService__sqlJS.findBookById as any;
+export const booksByAuthor: (params:booksByAuthorParams, client:PgTyped_Pg_Client_t) => Promise<booksByAuthorResult[]> = BookService__sqlJS.booksByAuthor as any;
 
 export const FindBookById: {
   /** Returns exactly 1 result. Raises `Exn.t` (with an optionally provided `errorMessage`) if more or less than exactly 1 result is returned. */