@ (#56)

Forge: fall back to the run jar when there is no @Args launcher (#42)

Pre-1.17 Forge (<=1.16.5) does not emit an OS @Args file; the installer
produces a runnable server jar instead. createServer only ever looked for
win_args.txt/unix_args.txt and threw installer-args-not-found for those
versions even though the install succeeded.

- New pure, unit-testable pickForgeRunJar() in serverDetect: given the
  top-level jar listing, pick the produced forge/neoforge run jar
  (universal on <=1.12, forge-<mcver>-<forgever>.jar on 1.13-1.16),
  skipping the installer jar itself.
- createServer: if no @Args file is found after the installer runs, fall
  back to launching that jar with -jar; only throw when neither exists.
  1.17+ Forge / NeoForge keep the @Args path unchanged.
- universal-first ordering is safe only because listJars is top-level
  only (documented in a comment so nobody makes it recursive).
- WIZARD smoke: cover the jar-vs-args decision (universal / loader / none,
  installer excluded, vanilla server jar never picked, neoforge keyword).

Scope: this fixes the installer-args-not-found failure only. Actually
launching an old-Forge server also needs a compatible JRE (Java 8), which
is the Java-provisioning / #44 matrix concern, not this change.


@

Co-authored-by: Claude Opus 4.8 <noreply@anthropic.com>

Author: CaYatur

src/main/core/createServer.ts

@@ -17,6 +17,34 @@ export function listJars(dir: string): string[] {
   }
 }
 
+/**
+ * After a Forge/NeoForge installer runs on a pre-1.17 version there is no
+ * `@args` launcher — the installer produces a runnable server jar instead
+ * (`forge-<ver>-universal.jar` on ≤1.12, `forge-<mcver>-<forgever>.jar` on
+ * 1.13–1.16). Pick that jar from the directory listing, skipping the installer
+ * jar itself. Pure (takes filenames) so it is unit-testable without a toolchain.
+ * Returns null when no loader run jar is present (caller then errors).
+ */
+export function pickForgeRunJar(
+  jarNames: string[],
+  installerJar: string,
+  type: ServerType
+): string | null {
+  const kw = type === 'neoforge' ? 'neoforge' : 'forge'
+  const lc = (j: string): string => j.toLowerCase()
+  const cand = jarNames.filter((j) => j !== installerJar && !lc(j).includes('installer'))
+  // universal-first is only correct because the caller passes a NON-recursive,
+  // top-level listing (listJars): on ≤1.12 the runnable `-universal.jar` sits at
+  // top level, while on 1.13–1.16 the top level has a plain `forge-<ver>.jar`
+  // and the `-universal.jar` lives under libraries/ (so it is never in scope).
+  // Do not switch the caller to a recursive scan or this ordering breaks.
+  return (
+    cand.find((j) => lc(j).includes(kw) && lc(j).includes('universal')) ||
+    cand.find((j) => lc(j).includes(kw)) ||
+    null
+  )
+}
+
 /** Pull a Minecraft version like 1.20.4 / 1.21 out of an arbitrary string. */
 export function guessVersion(s: string): string {
   const m = s.match(/\b1\.(\d{1,2})(?:\.(\d{1,2}))?\b/)

src/main/core/serverDetect.ts

@@ -15,6 +15,7 @@ import { pickSiteLang } from './web/siteLang'
 import type { Product } from '@shared/web'
 import { getProvider } from './core/versions'
 import { createServer } from './core/createServer'
+import { pickForgeRunJar } from './core/serverDetect'
 import { removeServer } from './core/serverRegistry'
 import * as sf from './core/serverFiles'
 import * as playersMod from './core/players'
@@ -2637,6 +2638,43 @@ export async function runWizardSmoke(): Promise<void> {
     return fail('fabric create threw: ' + String(e))
   }
 
+  // 3. Forge/NeoForge run-jar fallback for pre-1.17 (the installer itself needs
+  //    a real JDK, so exercise the pure jar-vs-args decision instead). #42
+  {
+    const inst12 = 'forge-1.12.2-14.23.5.2860-installer.jar'
+    const pick12 = pickForgeRunJar(
+      [inst12, 'forge-1.12.2-14.23.5.2860-universal.jar', 'minecraft_server.1.12.2.jar'],
+      inst12,
+      'forge'
+    )
+    if (pick12 !== 'forge-1.12.2-14.23.5.2860-universal.jar') {
+      return fail('pre-1.12 forge should pick the universal jar, got ' + pick12)
+    }
+    const inst16 = 'forge-1.16.5-36.2.39-installer.jar'
+    const pick16 = pickForgeRunJar([inst16, 'forge-1.16.5-36.2.39.jar'], inst16, 'forge')
+    if (pick16 !== 'forge-1.16.5-36.2.39.jar') {
+      return fail('1.16 forge should pick the loader run jar, got ' + pick16)
+    }
+    // 1.17+ leaves only the installer (it uses @args) -> no run jar to fall back to.
+    const inst20 = 'forge-1.20.1-47.2.0-installer.jar'
+    if (pickForgeRunJar([inst20], inst20, 'forge') !== null) {
+      return fail('1.17+ forge (installer only) should yield no run jar')
+    }
+    // Never pick the installer itself, and never a plain vanilla server jar.
+    if (pickForgeRunJar([inst12, 'minecraft_server.1.12.2.jar'], inst12, 'forge') !== null) {
+      return fail('forge fallback must not pick the installer or a vanilla server jar')
+    }
+    // NeoForge keyword is honoured (defensive; NeoForge is always 1.20.1+).
+    const instNeo = 'neoforge-20.4.100-installer.jar'
+    if (
+      pickForgeRunJar([instNeo, 'neoforge-20.4.100-universal.jar'], instNeo, 'neoforge') !==
+      'neoforge-20.4.100-universal.jar'
+    ) {
+      return fail('neoforge fallback should pick the neoforge universal jar')
+    }
+    console.log('WIZARD-SMOKE: forge run-jar fallback OK (universal/loader/none, installer excluded)')
+  }
+
   console.log('WIZARD-SMOKE: PASS')
   app.exit(0)
 }