Perf: fast sing-box JSON print

Build/build-reject-domainset.ts

@@ -19,7 +19,6 @@ import { OUTPUT_INTERNAL_DIR, SOURCE_DIR } from './constants/dir';
 import { DomainsetOutput, AdGuardHomeOutput } from './lib/rules/domainset';
 import { foundDebugDomain } from './lib/parse-filter/shared';
 import { createWorker } from './lib/worker';
-import { endOutputWorkerFarm } from './lib/rules/output-worker-farm';
 import type { MaybePromise } from './lib/misc';
 import { RulesetOutput } from './lib/rules/ruleset';
 import { fetchAssets } from './lib/fetch-assets';
@@ -308,8 +307,5 @@ export const buildRejectDomainSet = task(require.main === module, __filename)(as
     .addFromRuleset(readFileIntoProcessedArray(path.join(SOURCE_DIR, 'non_ip/my_reject.conf')))
     .write();
 
-  await Promise.all([
-    phishingWorker.end(),
-    endOutputWorkerFarm()
-  ]);
+  await phishingWorker.end();
 });

Build/index.ts

@@ -28,7 +28,7 @@ import path from 'node:path';
 import { ROOT_DIR } from './constants/dir';
 import { isCI } from 'ci-info';
 import { printExternalDownloadStats } from './lib/download-stats';
-import { endOutputWorkerFarm } from './lib/rules/output-worker-farm';
+import { endOutputWorkerFarm, warmOutputWorkerFarm } from './lib/rules/output-worker-farm';
 
 process.on('uncaughtException', (error) => {
   console.error('Uncaught exception:', error);
@@ -85,6 +85,11 @@ const buildFinishedLock = path.join(ROOT_DIR, '.BUILD_FINISHED');
     require.resolve('./download-mock-assets.worker')
   )(['downloadMockAssets']);
 
+  // Shared by any task whose FileOutput crosses the offload threshold. Booted here
+  // rather than inside a task so the ~250ms thread spin-up overlaps the downloads
+  // instead of landing on the critical path when the writes finally dispatch.
+  warmOutputWorkerFarm();
+
   try {
     // only enable why-is-node-running in GitHub Actions debug mode
     if (isCI && process.env.RUNNER_DEBUG === '1') {
@@ -132,7 +137,6 @@ const buildFinishedLock = path.join(ROOT_DIR, '.BUILD_FINISHED');
       cdnDownloadWorker.end(),
       telegramCidrWorker.end(),
       mockAssetsWorker.end(),
-      // defensive: no-op unless some FileOutput crossed the offload threshold
       endOutputWorkerFarm()
     ]);
 

Build/lib/rules/output-worker-farm.ts

@@ -21,6 +21,16 @@ export function getOutputWorkerFarm(): OutputWorkerFarm {
   return farm;
 }
 
+/**
+ * Boot the farm ahead of time. Spawning the threads costs ~200-300ms (each loads
+ * @swc-node/register and compiles the module graph), and since every big output
+ * dispatches at the very end of a task, that cost otherwise lands entirely on the
+ * critical path. Call this as early as the task starts so it overlaps the downloads.
+ */
+export function warmOutputWorkerFarm(): void {
+  getOutputWorkerFarm();
+}
+
 export async function endOutputWorkerFarm(): Promise<void> {
   if (farm) {
     const f = farm;

Build/lib/writing-strategy/singbox.ts

@@ -2,9 +2,9 @@ import { BaseWriteStrategy } from './base';
 import { appendArrayInPlace } from 'foxts/append-array-in-place';
 import { noop } from 'foxts/noop';
 import { withIdentityContent } from '../misc';
-import stringify from 'json-stringify-pretty-compact';
 import { OUTPUT_SINGBOX_DIR } from '../../constants/dir';
 import { MARKER_DOMAIN } from '../../constants/description';
+import { fastStringArrayJoin } from 'foxts/fast-string-array-join';
 
 interface SingboxHeadlessRule {
   domain: string[],
@@ -27,13 +27,91 @@ export interface SingboxSourceFormat {
   rules: SingboxHeadlessRule[]
 }
 
+/**
+ * json-stringify-pretty-compact spends most of its time re-serializing the whole
+ * subtree at every nesting level just to decide whether it fits on one line -- for
+ * a 145k-domain ruleset that is several full passes over a multi-megabyte string,
+ * plus a final split('\n').
+ *
+ * Our document shape is fixed (`{version, rules: [rule]}`, rule values are flat
+ * arrays of string/number), so we emit the lines directly and only probe as many
+ * items as it takes to know a line cannot fit.
+ */
+const SINGBOX_MAX_LENGTH = 120;
+/** rule values live at indent 6 */
+const RULE_VALUE_INDENT = 6;
+
+type SingboxRuleValue = string[] | number[];
+
+/** prettified JSON of `arr` when it fits `budget`, else null -- bails out early */
+function inlineIfFits(arr: SingboxRuleValue, budget: number): string | null {
+  if (arr.length === 0) {
+    return '[]';
+  }
+
+  let len = 2; // [ and ]
+  if (len > budget) {
+    return null;
+  }
+
+  const first = JSON.stringify(arr[0]);
+  len += first.length;
+  if (len > budget) {
+    return null;
+  }
+  const parts: string[] = [
+    first
+  ];
+  for (let i = 1, l = arr.length; i < l; i++) {
+    const item = JSON.stringify(arr[i]);
+    len += item.length + 2; // ', ' separator
+    if (len > budget) {
+      return null;
+    }
+    parts.push(item);
+  }
+  return '[' + fastStringArrayJoin(parts, ', ') + ']';
+}
+
+export function singboxSourceToLines(rule: SingboxHeadlessRule): string[] {
+  const keys = Object.keys(rule) as Array<keyof SingboxHeadlessRule>;
+  const lines: string[] = ['{', '  "version": 2,', '  "rules": [', '    {'];
+
+  for (let i = 0, l = keys.length; i < l; i++) {
+    const key = keys[i];
+    const arr = rule[key];
+    if (!Array.isArray(arr)) {
+      throw new TypeError('singbox rule source value is not an array');
+    }
+
+    const keyPart = JSON.stringify(key) + ': ';
+    const isLast = i === l - 1;
+    const trailing = isLast ? '' : ',';
+    // the library reserves the key prefix plus, unless last, the trailing comma
+    const budget = SINGBOX_MAX_LENGTH - RULE_VALUE_INDENT - (keyPart.length + (isLast ? 0 : 1));
+
+    const inlined = inlineIfFits(arr, budget);
+    if (inlined !== null) {
+      lines.push('      ' + keyPart + inlined + trailing);
+      continue;
+    }
+
+    lines.push('      ' + keyPart + '[');
+    for (let j = 0, l2 = arr.length; j < l2; j++) {
+      lines.push('        ' + JSON.stringify(arr[j]) + (j === l2 - 1 ? '' : ','));
+    }
+    lines.push('      ]' + trailing);
+  }
+
+  lines.push('    }', '  ]', '}');
+  return lines;
+}
+
 export class SingboxSource extends BaseWriteStrategy {
   public readonly name = 'singbox';
 
   readonly fileExtension = 'json';
 
-  static readonly jsonToLines = (json: unknown): string[] => stringify(json).split('\n');
-
   // JSON output has no metadata comment at all, nothing to preserve
   protected override readonly skipCompareOnCI = true;
 
@@ -43,10 +121,7 @@ export class SingboxSource extends BaseWriteStrategy {
   };
 
   protected get result() {
-    return SingboxSource.jsonToLines({
-      version: 2,
-      rules: [this.singbox]
-    });
+    return singboxSourceToLines(this.singbox);
   }
 
   constructor(

package.json

@@ -34,7 +34,6 @@
     "fnv1a52": "^1.0.0",
     "hash-wasm": "^4.12.0",
     "hntrie": "^1.1.0",
-    "json-stringify-pretty-compact": "4.0.0",
     "null-prototype-object": "^1.2.7",
     "picocolors": "^1.1.1",
     "tar-fs": "^3.1.3",

pnpm-lock.yaml

@@ -56,9 +56,6 @@ importers:
       hntrie:
         specifier: ^1.1.0
         version: 1.1.0
-      json-stringify-pretty-compact:
-        specifier: 4.0.0
-        version: 4.0.0
       null-prototype-object:
         specifier: ^1.2.7
         version: 1.2.7
@@ -1609,9 +1606,6 @@ packages:
   json-stable-stringify-without-jsonify@1.0.1:
     resolution: {integrity: sha512-Bdboy+l7tA3OGW6FjyFHWkP5LuByj1Tk33Ljyq0axyzdk9//JSi2u3fP1QSmd1KNwq6VOKYGlAu87CisVir6Pw==}
 
-  json-stringify-pretty-compact@4.0.0:
-    resolution: {integrity: sha512-3CNZ2DnrpByG9Nqj6Xo8vqbjT4F6N+tb4Gb28ESAZjYZ5yqvmc56J+/kuIwkaAMOyblTQhUW7PxMkUb8Q36N3Q==}
-
   jsonc-eslint-parser@3.1.0:
     resolution: {integrity: sha512-75EA7EWZExL/j+MDKQrRbdzcRI2HOkRlmUw8fZJc1ioqFEOvBsq7Rt+A6yCxOt9w/TYNpkt52gC6nm/g5tFIng==}
     engines: {node: ^20.19.0 || ^22.13.0 || >=24}
@@ -3468,8 +3462,6 @@ snapshots:
 
   json-stable-stringify-without-jsonify@1.0.1: {}
 
-  json-stringify-pretty-compact@4.0.0: {}
-
   jsonc-eslint-parser@3.1.0:
     dependencies:
       acorn: 8.16.0