Resolve GMAT root by exact wrapper path

- locateGmatRoot now checks exactly <staging>/GMAT/<version>/api/BuildApiStartupFile.py and returns <staging>/GMAT/<version>. The R2026a Linux tarball wraps the install in two levels (GMAT/R2026a/...); R2022a and R2025a use the same shape (verified against the live SourceForge tarballs). The previous depth-0/1 search overgeneralized from a single tarball and missed R2026a.
- extract(archivePath, version) now takes version; install.ts threads inputs.version through the orchestrator.
- Loud failure on layout drift: if the expected path is missing, the error names exactly which path was expected so the next bisect is one step.
- No discovery, no BFS, no scan. The supported-version matrix (R2022a, R2025a, R2026a — note R2023a/R2024a were never released) all match this layout; if a future release ever changes shape, we'll hear about it loudly and adapt with the actual evidence in hand.
- dist/index.js regenerated.

Closes #27

Author: djankov

dist/index.js

@@ -1,19 +1,19 @@
 import { existsSync } from 'node:fs';
-import { readdir } from 'node:fs/promises';
 import * as os from 'node:os';
 import * as path from 'node:path';
 import * as core from '@actions/core';
 import * as io from '@actions/io';
 import * as tc from '@actions/tool-cache';
+import type { GmatVersion } from './inputs';
 
 const API_STARTUP_FILE = path.join('api', 'BuildApiStartupFile.py');
 
-export async function extract(archivePath: string): Promise<string> {
+export async function extract(archivePath: string, version: GmatVersion): Promise<string> {
   core.info(`Extracting GMAT installer ${archivePath}`);
   const stagingDir = await tc.extractTar(archivePath);
   core.debug(`Extracted to ${stagingDir}`);
 
-  const stagedRoot = await locateGmatRoot(stagingDir);
+  const stagedRoot = locateGmatRoot(stagingDir, version);
   core.debug(`Resolved staged GMAT_ROOT: ${stagedRoot}`);
 
   const finalRoot = path.join(runnerTemp(), 'gmat');
@@ -26,21 +26,15 @@ export async function extract(archivePath: string): Promise<string> {
   return finalRoot;
 }
 
-async function locateGmatRoot(stagingDir: string): Promise<string> {
-  if (existsSync(path.join(stagingDir, API_STARTUP_FILE))) {
-    return stagingDir;
-  }
-  const entries = await readdir(stagingDir, { withFileTypes: true });
-  for (const entry of entries) {
-    if (!entry.isDirectory()) continue;
-    const candidate = path.join(stagingDir, entry.name);
-    if (existsSync(path.join(candidate, API_STARTUP_FILE))) {
-      return candidate;
-    }
+function locateGmatRoot(stagingDir: string, version: GmatVersion): string {
+  const expectedRoot = path.join(stagingDir, 'GMAT', version);
+  if (existsSync(path.join(expectedRoot, API_STARTUP_FILE))) {
+    return expectedRoot;
   }
   throw new Error(
-    `Could not locate ${API_STARTUP_FILE} under ${stagingDir}. ` +
-      `The installer archive layout may have changed.`,
+    `Expected GMAT/${version}/${API_STARTUP_FILE} inside the installer, ` +
+      `but ${path.join(expectedRoot, API_STARTUP_FILE)} is missing. ` +
+      `Did the upstream archive layout change?`,
   );
 }
 

src/extract.ts

@@ -35,7 +35,9 @@ async function resolveInstall(inputs: Inputs): Promise<{ gmatRoot: string; cache
   const archive = await core.group(`Download GMAT ${inputs.version}`, () =>
     download(inputs.version),
   );
-  const gmatRoot = await core.group('Extract GMAT installer', () => extract(archive));
+  const gmatRoot = await core.group('Extract GMAT installer', () =>
+    extract(archive, inputs.version),
+  );
 
   if (inputs.cache) {
     await core.group('Save GMAT cache', () => saveCache(inputs.version, gmatRoot));