V5 bringing RESP3, Sentinel and TypeMapping to node-redis

RESP3 Support
   - Some commands responses in RESP3 aren't stable yet and therefore return an "untyped" ReplyUnion.
 
Sentinel

TypeMapping

Correctly types Multi commands

Note: some API changes to be further documented in v4-to-v5.md

packages/client/lib/commands/FUNCTION_STATS.ts

@@ -1,56 +1,70 @@
-import { RedisCommandArguments } from '.';
+import { Command, TuplesToMapReply, BlobStringReply, NullReply, NumberReply, MapReply, Resp2Reply, UnwrapReply } from '../RESP/types';
+import { isNullReply } from './generic-transformers';
 
-export function transformArguments(): RedisCommandArguments {
+type RunningScript = NullReply | TuplesToMapReply<[
+  [BlobStringReply<'name'>, BlobStringReply],
+  [BlobStringReply<'command'>, BlobStringReply],
+  [BlobStringReply<'duration_ms'>, NumberReply]
+]>;
+
+type Engine = TuplesToMapReply<[
+  [BlobStringReply<'libraries_count'>, NumberReply],
+  [BlobStringReply<'functions_count'>, NumberReply]
+]>;
+
+type Engines = MapReply<BlobStringReply, Engine>;
+
+type FunctionStatsReply = TuplesToMapReply<[
+  [BlobStringReply<'running_script'>, RunningScript],
+  [BlobStringReply<'engines'>, Engines]
+]>;
+
+export default {
+  IS_READ_ONLY: true,
+  FIRST_KEY_INDEX: undefined,
+  transformArguments() {
     return ['FUNCTION', 'STATS'];
+  },
+  transformReply: {
+    2: (reply: UnwrapReply<Resp2Reply<FunctionStatsReply>>) => {
+      return {
+        running_script: transformRunningScript(reply[1]),
+        engines: transformEngines(reply[3])
+      };
+    },
+    3: undefined as unknown as () => FunctionStatsReply
+  }
+} as const satisfies Command;
+
+function transformRunningScript(reply: Resp2Reply<RunningScript>) {
+  if (isNullReply(reply)) {
+    return null;
+  }
+
+  const unwraped = reply as unknown as UnwrapReply<typeof reply>;
+  return {
+    name: unwraped[1],
+    command: unwraped[3],
+    duration_ms: unwraped[5]
+  };
 }
 
-type FunctionStatsRawReply = [
-    'running_script',
-    null | [
-        'name',
-        string,
-        'command',
-        string,
-        'duration_ms',
-        number
-    ],
-    'engines',
-    Array<any> // "flat tuples" (there is no way to type that)
-    // ...[string, [
-    //     'libraries_count',
-    //     number,
-    //     'functions_count',
-    //     number
-    // ]]
-];
+function transformEngines(reply: Resp2Reply<Engines>) {
+  const unwraped = reply as unknown as UnwrapReply<typeof reply>;
 
-interface FunctionStatsReply {
-    runningScript: null | {
-        name: string;
-        command: string;
-        durationMs: number;
+  const engines: Record<string, {
+    libraries_count: NumberReply;
+    functions_count: NumberReply;
+  }> = Object.create(null);
+  for (let i = 0; i < unwraped.length; i++) {
+    const name = unwraped[i] as BlobStringReply,
+      stats = unwraped[++i] as Resp2Reply<Engine>,
+      unwrapedStats = stats as unknown as UnwrapReply<typeof stats>;
+    engines[name.toString()] = {
+      libraries_count: unwrapedStats[1],
+      functions_count: unwrapedStats[3]
     };
-    engines: Record<string, {
-        librariesCount: number;
-        functionsCount: number;
-    }>;
-}
+  }
 
-export function transformReply(reply: FunctionStatsRawReply): FunctionStatsReply {
-    const engines = Object.create(null);
-    for (let i = 0; i < reply[3].length; i++) {
-        engines[reply[3][i]] = {
-            librariesCount: reply[3][++i][1],
-            functionsCount: reply[3][i][3]
-        };
-    }
-
-    return {
-        runningScript: reply[1] === null ? null : {
-            name: reply[1][1],
-            command: reply[1][3],
-            durationMs: reply[1][5]
-        },
-        engines
-    };
+  return engines;
 }