Add lit method to expression builder (#600)

src/expression/expression-builder.ts

@@ -52,6 +52,7 @@ import { SqlBool } from '../util/type-utils.js'
 import { parseUnaryOperation } from '../parser/unary-operation-parser.js'
 import {
   ExtractTypeFromValueExpressionOrList,
+  parseSafeImmediateValue,
   parseValueExpressionOrList,
 } from '../parser/value-parser.js'
 import { NOOP_QUERY_EXECUTOR } from '../query-executor/noop-query-executor.js'
@@ -420,6 +421,30 @@ export interface ExpressionBuilder<DB, TB extends keyof DB> {
     value: VE
   ): ExpressionWrapper<DB, TB, ExtractTypeFromValueExpressionOrList<VE>>
 
+  /**
+   * Returns a literal value expression.
+   *
+   * Just like `val` but creates a literal value that gets merged in the SQL.
+   * To prevent SQL injections, only `boolean`, `number` and `null` values
+   * are accepted. If you need `string` or other literals, use `sql.lit` instead.
+   *
+   * ### Examples
+   *
+   * ```ts
+   * db.selectFrom('person')
+   *   .select((eb) => eb.lit(1).as('one'))
+   * ```
+   *
+   * The generated SQL (PostgreSQL):
+   *
+   * ```sql
+   * select 1 as "one" from "person"
+   * ```
+   */
+  lit<VE extends number | boolean | null>(
+    literal: VE
+  ): ExpressionWrapper<DB, TB, VE>
+
   /**
    * @deprecated Use the expression builder as a function instead.
    *
@@ -811,6 +836,12 @@ export function createExpressionBuilder<DB, TB extends keyof DB>(
       return new ExpressionWrapper(parseValueExpressionOrList(value))
     },
 
+    lit<VE extends number | boolean | null>(
+      value: VE
+    ): ExpressionWrapper<DB, TB, VE> {
+      return new ExpressionWrapper(parseSafeImmediateValue(value))
+    },
+
     // @deprecated
     cmpr<
       O extends SqlBool = SqlBool,

test/node/src/expression.test.ts

@@ -68,12 +68,14 @@ for (const dialect of DIALECTS) {
                 first_name: eb.ref('last_name'),
                 last_name: eb.ref('first_name'),
               }),
+              // Boolean literal
+              eb.lit(true),
             ])
         )
 
       testSql(query, dialect, {
         postgres: {
-          sql: 'select "person".* from "person" where ((not "first_name" = $1 or "id" + $2 > $3 or "id" in ($4, $5, $6) or upper("first_name") = $7 or false) and exists (select "pet"."id" from "pet" where "pet"."owner_id" = "person"."id") and true and ("id" = $8 or "id" = $9 or "id" = $10 or "id" = $11) and ("id" = $12 and "first_name" = $13 and "last_name" = $14 and "marital_status" = $15) and ("id" = $16 or "id" = $17) and ("id" + $18) > $19 and ("first_name" = $20 and "last_name" = $21) and ("first_name" = "last_name" or "last_name" = "first_name"))',
+          sql: 'select "person".* from "person" where ((not "first_name" = $1 or "id" + $2 > $3 or "id" in ($4, $5, $6) or upper("first_name") = $7 or false) and exists (select "pet"."id" from "pet" where "pet"."owner_id" = "person"."id") and true and ("id" = $8 or "id" = $9 or "id" = $10 or "id" = $11) and ("id" = $12 and "first_name" = $13 and "last_name" = $14 and "marital_status" = $15) and ("id" = $16 or "id" = $17) and ("id" + $18) > $19 and ("first_name" = $20 and "last_name" = $21) and ("first_name" = "last_name" or "last_name" = "first_name") and true)',
           parameters: [
             'Jennifer',
             1,
@@ -99,7 +101,7 @@ for (const dialect of DIALECTS) {
           ],
         },
         mysql: {
-          sql: 'select `person`.* from `person` where ((not `first_name` = ? or `id` + ? > ? or `id` in (?, ?, ?) or upper(`first_name`) = ? or false) and exists (select `pet`.`id` from `pet` where `pet`.`owner_id` = `person`.`id`) and true and (`id` = ? or `id` = ? or `id` = ? or `id` = ?) and (`id` = ? and `first_name` = ? and `last_name` = ? and `marital_status` = ?) and (`id` = ? or `id` = ?) and (`id` + ?) > ? and (`first_name` = ? and `last_name` = ?) and (`first_name` = `last_name` or `last_name` = `first_name`))',
+          sql: 'select `person`.* from `person` where ((not `first_name` = ? or `id` + ? > ? or `id` in (?, ?, ?) or upper(`first_name`) = ? or false) and exists (select `pet`.`id` from `pet` where `pet`.`owner_id` = `person`.`id`) and true and (`id` = ? or `id` = ? or `id` = ? or `id` = ?) and (`id` = ? and `first_name` = ? and `last_name` = ? and `marital_status` = ?) and (`id` = ? or `id` = ?) and (`id` + ?) > ? and (`first_name` = ? and `last_name` = ?) and (`first_name` = `last_name` or `last_name` = `first_name`) and true)',
           parameters: [
             'Jennifer',
             1,
@@ -125,7 +127,7 @@ for (const dialect of DIALECTS) {
           ],
         },
         sqlite: {
-          sql: 'select "person".* from "person" where ((not "first_name" = ? or "id" + ? > ? or "id" in (?, ?, ?) or upper("first_name") = ? or false) and exists (select "pet"."id" from "pet" where "pet"."owner_id" = "person"."id") and true and ("id" = ? or "id" = ? or "id" = ? or "id" = ?) and ("id" = ? and "first_name" = ? and "last_name" = ? and "marital_status" = ?) and ("id" = ? or "id" = ?) and ("id" + ?) > ? and ("first_name" = ? and "last_name" = ?) and ("first_name" = "last_name" or "last_name" = "first_name"))',
+          sql: 'select "person".* from "person" where ((not "first_name" = ? or "id" + ? > ? or "id" in (?, ?, ?) or upper("first_name") = ? or false) and exists (select "pet"."id" from "pet" where "pet"."owner_id" = "person"."id") and true and ("id" = ? or "id" = ? or "id" = ? or "id" = ?) and ("id" = ? and "first_name" = ? and "last_name" = ? and "marital_status" = ?) and ("id" = ? or "id" = ?) and ("id" + ?) > ? and ("first_name" = ? and "last_name" = ?) and ("first_name" = "last_name" or "last_name" = "first_name") and true)',
           parameters: [
             'Jennifer',
             1,

test/node/src/where.test.ts

@@ -671,25 +671,25 @@ for (const dialect of DIALECTS) {
         const query = ctx.db
           .selectFrom('person')
           .selectAll()
-          .where(({ exists, selectFrom }) =>
+          .where(({ exists, selectFrom, lit }) =>
             exists(
               selectFrom('pet')
-                .select('pet.id')
+                .select(lit(1).as('exists'))
                 .whereRef('pet.owner_id', '=', 'person.id')
             )
           )
 
         testSql(query, dialect, {
           postgres: {
-            sql: 'select * from "person" where exists (select "pet"."id" from "pet" where "pet"."owner_id" = "person"."id")',
+            sql: 'select * from "person" where exists (select 1 as "exists" from "pet" where "pet"."owner_id" = "person"."id")',
             parameters: [],
           },
           mysql: {
-            sql: 'select * from `person` where exists (select `pet`.`id` from `pet` where `pet`.`owner_id` = `person`.`id`)',
+            sql: 'select * from `person` where exists (select 1 as `exists` from `pet` where `pet`.`owner_id` = `person`.`id`)',
             parameters: [],
           },
           sqlite: {
-            sql: 'select * from "person" where exists (select "pet"."id" from "pet" where "pet"."owner_id" = "person"."id")',
+            sql: 'select * from "person" where exists (select 1 as "exists" from "pet" where "pet"."owner_id" = "person"."id")',
             parameters: [],
           },
         })

test/typings/test-d/expression.test-d.ts

@@ -80,6 +80,10 @@ function testExpressionBuilder(eb: ExpressionBuilder<Database, 'person'>) {
     ])
   )
 
+  expectAssignable<Expression<1>>(eb.lit(1))
+  expectAssignable<Expression<boolean>>(eb.lit(true))
+  expectAssignable<Expression<null>>(eb.lit(null))
+
   expectAssignable<Expression<SqlBool>>(
     eb.and({
       'person.age': 10,
@@ -127,4 +131,7 @@ function testExpressionBuilder(eb: ExpressionBuilder<Database, 'person'>) {
 
   expectError(eb.or({ unknown_column: 'Jennifer' }))
   expectError(eb.or({ age: 'wrong type' }))
+
+  // String literals are not allowed.
+  expectError(eb.lit('foobar'))
 }