Handle column name embed

Author: wyozi

src/select-query-parser.ts

@@ -66,25 +66,34 @@ type EatWhitespace<Input extends string> = string extends Input
   ? EatWhitespace<Remainder>
   : Input
 
-type HasFKey<FKeyName, Relationships> = Relationships extends [infer R]
-  ? R extends { foreignKeyName: FKeyName }
+type InArray<Item, Array> = Array extends [infer I]
+  ? I extends Item
     ? true
     : false
-  : Relationships extends [infer R, ...infer Rest]
-  ? HasFKey<FKeyName, [R]> extends true
+  : Array extends [infer I, ...infer Rest]
+  ? InArray<Item, [I]> extends true
     ? true
-    : HasFKey<FKeyName, Rest>
+    : InArray<Item, Rest>
   : false
 
-type HasFKeyToFRel<FRelName, Relationships> = Relationships extends [infer R]
-  ? R extends { referencedRelation: FRelName }
-    ? true
-    : false
+type HasFKey<FKeyName, Relationships> = InArray<{ foreignKeyName: FKeyName }, Relationships>
+
+type HasFKeyToFRel<FRelName, Relationships> = InArray<
+  { referencedRelation: FRelName },
+  Relationships
+>
+
+type ColumnForeignRelation<ColName, Relationships> = Relationships extends [infer R]
+  ? R extends { columns: string[]; referencedRelation: string }
+    ? InArray<ColName, R['columns']> extends true
+      ? [R['referencedRelation']]
+      : null
+    : null
   : Relationships extends [infer R, ...infer Rest]
-  ? HasFKeyToFRel<FRelName, [R]> extends true
-    ? true
-    : HasFKeyToFRel<FRelName, Rest>
-  : false
+  ? ColumnForeignRelation<ColName, [R]> extends [infer Rel]
+    ? [Rel]
+    : ColumnForeignRelation<ColName, Rest>
+  : null
 
 /**
  * Constructs a type definition for a single field of an object.
@@ -119,23 +128,39 @@ type ConstructFieldDefinition<
         : never
     }
   : Field extends { name: string; original: string; children: unknown[] }
-  ? {
-      [_ in Field['name']]: GetResultHelper<
-        Schema,
-        (Schema['Tables'] & Schema['Views'])[Field['original']]['Row'],
-        (Schema['Tables'] & Schema['Views'])[Field['original']] extends { Relationships: infer R }
-          ? R
-          : unknown,
-        Field['children'],
-        unknown
-      > extends infer Child
-        ? Relationships extends unknown[]
-          ? HasFKeyToFRel<Field['original'], Relationships> extends true
-            ? Child | null
+  ? ColumnForeignRelation<Field['original'], Relationships> extends [infer ForeignRel]
+    ? // handle `col:foreign_key_column`
+      ForeignRel extends keyof (Schema['Tables'] & Schema['Views'])
+      ? {
+          [_ in Field['name']]: GetResultHelper<
+            Schema,
+            (Schema['Tables'] & Schema['Views'])[ForeignRel]['Row'],
+            (Schema['Tables'] & Schema['Views'])[ForeignRel] extends { Relationships: infer R }
+              ? R
+              : unknown,
+            Field['children'],
+            unknown
+          > | null
+        }
+      : SelectQueryError<`Unknown relation in a relationship`>
+    : // handle `col:relation`
+      {
+        [_ in Field['name']]: GetResultHelper<
+          Schema,
+          (Schema['Tables'] & Schema['Views'])[Field['original']]['Row'],
+          (Schema['Tables'] & Schema['Views'])[Field['original']] extends { Relationships: infer R }
+            ? R
+            : unknown,
+          Field['children'],
+          unknown
+        > extends infer Child
+          ? Relationships extends unknown[]
+            ? HasFKeyToFRel<Field['original'], Relationships> extends true
+              ? Child | null
+              : Child[]
             : Child[]
-          : Child[]
-        : never
-    }
+          : never
+      }
   : Field extends { name: string; original: string }
   ? Field['original'] extends keyof Row
     ? { [K in Field['name']]: Row[Field['original']] }

test/index.test-d.ts

@@ -74,6 +74,30 @@ const postgrest = new PostgrestClient<Database>(REST_URL)
   expectType<Database['public']['Tables']['users']['Row'] | null>(message.user)
 }
 
+// many-to-one relationship (fkey)
+{
+  const { data: message, error } = await postgrest
+    .from('messages')
+    .select('user:users!messages_username_fkey(*)')
+    .single()
+  if (error) {
+    throw new Error(error.message)
+  }
+  expectType<Database['public']['Tables']['users']['Row'] | null>(message.user)
+}
+
+// many-to-one relationship (column name)
+{
+  const { data: message, error } = await postgrest
+    .from('messages')
+    .select('user:username(*)')
+    .single()
+  if (error) {
+    throw new Error(error.message)
+  }
+  expectType<Database['public']['Tables']['users']['Row'] | null>(message.user)
+}
+
 // one-to-many relationship
 {
   const { data: user, error } = await postgrest.from('users').select('messages(*)').single()