allow selecting nested paths, fix type inference when grouping nested…

… paths

README.md

@@ -32,8 +32,8 @@ interface Machine {
   mode: 'idle' | 'running';
   tags: string[];
   softDeleted?: {
-    atDate: string;
-    byUser: string;
+    at: string;
+    by: string;
   };
 }
 ```
@@ -51,7 +51,7 @@ const { querySpec } = new CosmosQueryBuilder<Machine>()
     d.isUndefined('softDeleted');
     d.and((c) => {
       c.isDefined('softDeleted');
-      c.lower('softDeleted.atDate', '2023-03-01'); // 👈 nested keys are also supported
+      c.lower('softDeleted.at', '2023-03-01'); // 👈 nested keys are also supported
     });
   })
   .orderBy('serial')
@@ -75,7 +75,7 @@ The result is a `SqlQuerySpec` that you can pass to the `Items.query()` function
       NOT IS_DEFINED(c.softDeleted)
       OR (
         IS_DEFINED(c.softDeleted)
-        AND c.softDeleted.atDate < @softDeleted_atDate
+        AND c.softDeleted.at < @softDeleted_at
       )
     )
     ORDER BY c.serial ASC
@@ -84,7 +84,7 @@ The result is a `SqlQuerySpec` that you can pass to the `Items.query()` function
   "parameters": [
     { "name": "@id", "value": "^0001-abc-.*" },
     { "name": "@mode", "value": ["idle", "running"] },
-    { "name": "@softDeleted_atDate", "value": "2023-03-01" }
+    { "name": "@softDeleted_at", "value": "2023-03-01" }
   ]
 }
 ```
@@ -104,10 +104,10 @@ const { resources } = await new CosmosQueryBuilder<Machine>().select('id', 'mode
 
 ### Selecting
 
-By default the whole document is selected with `SELECT * from c`. The `select()` function let's you defined which fields to query. As of now it is only possible to pass root keys here, nested keys are not supported yet.
+By default the whole document is selected with `SELECT * from c`. The `select()` function let's you define which fields or paths to query.
 
 ```ts
-.select('id', 'serial', 'isConnected')
+.select('id', 'serial', 'isConnected', 'softDeletd.at')
 ```
 
 Alternatively you can use any of those aggregation functions:

src/CosmosQueryBuilder.spec.ts

@@ -59,7 +59,7 @@ GROUP BY c.mode, c.softDeleted.by",
     const container = new CosmosClient('').database('').container('');
     // eslint-disable-next-line @typescript-eslint/no-unused-vars
     const { resources } = await new CosmosQueryBuilder<Machine>()
-      .selectSum('price', { groupBy: ['mode', 'id'] })
+      .selectSum('price', { groupBy: ['softDeleted.at', 'mode'] })
       .equals('id', '123')
       .build()
       .query(container)

src/CosmosQueryBuilder.ts

@@ -1,6 +1,6 @@
 import type { Container, SqlParameter, SqlQuerySpec, JSONValue, FeedOptions } from '@azure/cosmos';
 import { unpretty } from './helpers';
-import type { ArrayElement, Path, PathValue } from './typeHelpers';
+import type { ArrayElement, Path, PathValue, PickPath, UnionToIntersection } from './typeHelpers';
 
 const TAB = '  ';
 
@@ -225,7 +225,7 @@ type SortOrder = 'ASC' | 'DESC';
 
 export class CosmosQueryBuilder<
   T extends Record<string, any>,
-  S extends Pick<T, any> | Record<string, any> = T
+  S extends UnionToIntersection<PickPath<T, Path<T>>> | Record<string, any> = T
 > extends ConjunctionQueryBuilder<T> {
   private selection: string[] = [];
   private sorting: Array<{ by: string; order: SortOrder }> = [];
@@ -247,13 +247,15 @@ export class CosmosQueryBuilder<
     this.build = this.build.bind(this);
   }
 
-  select<F extends keyof T, NewS extends Pick<S, F>>(...fields: F[]): CosmosQueryBuilder<T, NewS> {
-    this.selection = fields.map((f) => `c.${String(f)}`);
+  select<P extends Path<T>, NewS extends UnionToIntersection<PickPath<T, P>>>(
+    ...paths: P[]
+  ): CosmosQueryBuilder<T, NewS> {
+    this.selection = paths.map((p) => `c.${String(p)}`);
     // @ts-ignore required for well-typed response when using the query() function
     return this;
   }
 
-  selectCount<GroupBy extends Path<T>, NewS extends Pick<T, GroupBy> & { count: number }>({
+  selectCount<GroupBy extends Path<T>, NewS extends UnionToIntersection<PickPath<T, GroupBy>> & { count: number }>({
     groupBy,
   }: { groupBy?: GroupBy | GroupBy[] } = {}): CosmosQueryBuilder<T, NewS> {
     this.selection = ['count(1) as count'];
@@ -262,20 +264,22 @@ export class CosmosQueryBuilder<
     return this;
   }
 
-  selectMax<P extends Path<T>, GroupBy extends Path<T>, NewS extends Pick<T, GroupBy> & { max: PathValue<T, P> }>(
-    path: P,
-    { groupBy }: { groupBy?: GroupBy | GroupBy[] } = {}
-  ): CosmosQueryBuilder<T, NewS> {
+  selectMax<
+    P extends Path<T>,
+    GroupBy extends Path<T>,
+    NewS extends UnionToIntersection<PickPath<T, GroupBy>> & { max: PathValue<T, P> }
+  >(path: P, { groupBy }: { groupBy?: GroupBy | GroupBy[] } = {}): CosmosQueryBuilder<T, NewS> {
     this.selection = [`MAX(c.${String(path)}) as max`];
     this.groupBy(groupBy);
     // @ts-ignore required for well-typed response when using the query() function
     return this;
   }
 
-  selectMin<P extends Path<T>, GroupBy extends Path<T>, NewS extends Pick<T, GroupBy> & { min: PathValue<T, P> }>(
-    path: P,
-    { groupBy }: { groupBy?: GroupBy | GroupBy[] } = {}
-  ): CosmosQueryBuilder<T, NewS> {
+  selectMin<
+    P extends Path<T>,
+    GroupBy extends Path<T>,
+    NewS extends UnionToIntersection<PickPath<T, GroupBy>> & { min: PathValue<T, P> }
+  >(path: P, { groupBy }: { groupBy?: GroupBy | GroupBy[] } = {}): CosmosQueryBuilder<T, NewS> {
     this.selection = [`MIN(c.${String(path)}) as min`];
     this.groupBy(groupBy);
     // @ts-ignore required for well-typed response when using the query() function
@@ -285,7 +289,7 @@ export class CosmosQueryBuilder<
   selectSum<
     P extends Exclude<Path<T>, NonNullable<PathValue<T, P>> extends number ? never : P>,
     GroupBy extends Path<T>,
-    NewS extends Pick<T, GroupBy> & { sum: PathValue<T, P> }
+    NewS extends UnionToIntersection<PickPath<T, GroupBy>> & { sum: PathValue<T, P> }
   >(path: P, { groupBy }: { groupBy?: GroupBy | GroupBy[] } = {}): CosmosQueryBuilder<T, NewS> {
     this.selection = [`SUM(c.${String(path)}) as sum`];
     this.groupBy(groupBy);
@@ -296,7 +300,7 @@ export class CosmosQueryBuilder<
   selectAvg<
     P extends Exclude<Path<T>, NonNullable<PathValue<T, P>> extends number ? never : P>,
     GroupBy extends Path<T>,
-    NewS extends Pick<T, GroupBy> & { avg: PathValue<T, P> }
+    NewS extends UnionToIntersection<PickPath<T, GroupBy>> & { avg: PathValue<T, P> }
   >(path: P, { groupBy }: { groupBy?: GroupBy | GroupBy[] } = {}): CosmosQueryBuilder<T, NewS> {
     this.selection = [`AVG(c.${String(path)}) as min`];
     this.groupBy(groupBy);

src/typeHelpers.ts

@@ -1,5 +1,7 @@
 export type ArrayElement<T> = T extends Array<infer Element> ? Element : never;
 
+export type UnionToIntersection<T> = (T extends any ? (x: T) => any : never) extends (x: infer R) => any ? R : never;
+
 type PathImpl<T, Key extends keyof T> = Key extends string
   ? Required<T>[Key] extends Record<string, any>
     ? Required<T>[Key] extends any[]
@@ -21,3 +23,13 @@ export type PathValue<T, P extends Path<T>> = P extends `${infer Key}.${infer Re
   : P extends keyof T
   ? T[P]
   : never;
+
+export type PickPath<T, P extends Path<T>> = P extends keyof T
+  ? Pick<T, P>
+  : P extends `${infer Key}.${infer Rest}`
+  ? Key extends keyof T
+    ? Rest extends Path<Required<T>[Key]>
+      ? PickPath<Required<T>[Key], Rest>
+      : never
+    : never
+  : never;