handle when condition parsing.

src/parser/binary-operation-parser.ts

@@ -36,6 +36,8 @@ import { SelectType } from '../util/column-type.js'
 import { AndNode } from '../operation-node/and-node.js'
 import { ParensNode } from '../operation-node/parens-node.js'
 import { OrNode } from '../operation-node/or-node.js'
+import { WhenNode } from '../operation-node/when-node.js'
+import { RawNode } from '../operation-node/raw-node.js'
 
 export type OperandValueExpression<
   DB,
@@ -153,6 +155,21 @@ export function parseFilterList(
   return node
 }
 
+export function parseMergeWhenCondition(
+  isMatched: boolean,
+  and: Expression<any> | undefined
+) {
+  return WhenNode.create(
+    parseFilterList(
+      [
+        RawNode.create([isMatched ? 'matched' : 'not matched'], []),
+        ...(and ? [and] : []),
+      ],
+      'and'
+    )
+  )
+}
+
 function isIsOperator(
   operator: BinaryOperatorExpression
 ): operator is 'is' | 'is not' {

src/query-builder/merge-query-builder.ts

@@ -4,14 +4,13 @@ import {
 } from '../expression/expression-builder.js'
 import { AliasedExpression, Expression } from '../expression/expression.js'
 import { MergeQueryNode } from '../operation-node/merge-query-node'
-import { UsingNode } from '../operation-node/using-node.js'
+import { parseMergeWhenCondition } from '../parser/binary-operation-parser.js'
 import {
   JoinCallbackExpression,
   JoinReferenceExpression,
   parseJoin,
 } from '../parser/join-parser.js'
 import { TableExpression } from '../parser/table-parser.js'
-import { UpdateObjectExpression } from '../parser/update-set-parser.js'
 import { CompiledQuery } from '../query-compiler/compiled-query.js'
 import { QueryExecutor } from '../query-executor/query-executor.js'
 import { Compilable } from '../util/compilable.js'
@@ -52,7 +51,7 @@ export class MergeQueryBuilder<DB, IT extends keyof DB> {
 
 preventAwait(
   MergeQueryBuilder,
-  "don't await MergeQueryBuilder instances directly. To execute the query you need to call `execute` or `executeTakeFirst`."
+  "don't await MergeQueryBuilder instances directly. To execute the query you need to call `execute` when available."
 )
 
 export interface MergeQueryBuilderProps {
@@ -78,10 +77,10 @@ export class WheneableMergeQueryBuilder<
   ): MatchedMergeQueryBuilder<DB, IT, UT> {
     return new MatchedMergeQueryBuilder({
       ...this.#props,
-      // queryNode: MergeQueryNode.cloneWithWhen(
-      // this.#props.queryNode,
-      // and?.(createExpressionBuilder()) // ??!
-      // ),
+      queryNode: MergeQueryNode.cloneWithWhen(
+        this.#props.queryNode,
+        parseMergeWhenCondition(true, and?.(createExpressionBuilder()))
+      ),
     })
   }
 
@@ -90,10 +89,10 @@ export class WheneableMergeQueryBuilder<
   ): NotMatchedMergeQueryBuilder<DB, IT, UT> {
     return new NotMatchedMergeQueryBuilder({
       ...this.#props,
-      // queryNode: MergeQueryNode.cloneWithWhen(
-      //   this.#props.queryNode,
-      //   and?.(createExpressionBuilder()) // ??!
-      // ),
+      queryNode: MergeQueryNode.cloneWithWhen(
+        this.#props.queryNode,
+        parseMergeWhenCondition(false, and?.(createExpressionBuilder()))
+      ),
     })
   }