Fix tar error in Git Bash on Windows

server/loader/npm.ts

@@ -1,4 +1,4 @@
-import { exec } from 'node:child_process'
+import { execFile } from 'node:child_process'
 import { rmSync } from 'node:fs'
 import { mkdtemp, rm, writeFile } from 'node:fs/promises'
 import { tmpdir } from 'node:os'
@@ -12,7 +12,7 @@ import type {
 } from '../../common/types.ts'
 
 const DOWNLOADED_PACKAGES = new Map<string, FilePath>()
-const execAsync = promisify(exec)
+const execFileAsync = promisify(execFile)
 
 function isGitUrl(version: DependencyVersion): boolean {
   return (
@@ -89,13 +89,22 @@ export async function getNpmContent(
 
     let tarballBuffer = await downloadTarball(tarballUrl)
     let tempDir = await mkdtemp(join(tmpdir(), 'multiocular-'))
-    let tarballPath = join(tempDir, 'package.tgz')
 
-    await writeFile(tarballPath, Buffer.from(tarballBuffer))
-    await execAsync(
-      `tar -xzf "${tarballPath}" --strip-components=1 -C "${tempDir}"`
-    )
-    await rm(tarballPath)
+    try {
+      let tarballPath = join(tempDir, 'package.tgz')
+      await writeFile(tarballPath, Buffer.from(tarballBuffer))
+
+      await execFileAsync(
+        'tar',
+        ['-xzf', 'package.tgz', '--strip-components=1'],
+        { cwd: tempDir }
+      )
+
+      await rm(tarballPath)
+    } catch (error) {
+      await rm(tempDir, { force: true, recursive: true })
+      throw error
+    }
 
     DOWNLOADED_PACKAGES.set(spec, tempDir as FilePath)
   }

server/test/tar.test.ts

@@ -0,0 +1,101 @@
+import { deepEqual, equal, match, rejects } from 'node:assert/strict'
+import { execSync } from 'node:child_process'
+import { existsSync } from 'node:fs'
+import {
+  chmod,
+  mkdtemp,
+  readdir,
+  readFile,
+  rm,
+  writeFile
+} from 'node:fs/promises'
+import { tmpdir } from 'node:os'
+import { join } from 'node:path'
+import { afterEach, test } from 'node:test'
+
+import type {
+  DependencyName,
+  DependencyVersion,
+  FilePath
+} from '../../common/types.ts'
+import { deleteTemporary, getNpmContent } from '../loader/npm.ts'
+
+let shimDir: string | undefined
+let originalPath = process.env.PATH
+
+afterEach(async () => {
+  process.env.PATH = originalPath
+  deleteTemporary()
+  if (shimDir) {
+    await rm(shimDir, { force: true, recursive: true })
+    shimDir = undefined
+  }
+})
+
+async function forbidAbsolutePathsInTar(): Promise<void> {
+  let real = execSync('command -v tar').toString().trim()
+  shimDir = await mkdtemp(join(tmpdir(), 'multiocular-shim-'))
+  let shim = join(shimDir, 'tar')
+  await writeFile(
+    shim,
+    '#!/bin/sh\n' +
+      'for arg in "$@"; do\n' +
+      '  case "$arg" in\n' +
+      '    /*)\n' +
+      '      echo "tar: absolute path $arg is not portable" >&2\n' +
+      '      exit 128\n' +
+      '      ;;\n' +
+      '  esac\n' +
+      'done\n' +
+      `exec "${real}" "$@"\n`
+  )
+  await chmod(shim, 0o755)
+  process.env.PATH = `${shimDir}:${originalPath}`
+}
+
+async function makeTarFail(): Promise<void> {
+  shimDir = await mkdtemp(join(tmpdir(), 'multiocular-shim-'))
+  let shim = join(shimDir, 'tar')
+  await writeFile(
+    shim,
+    '#!/bin/sh\necho "tar: simulated extraction failure" >&2\nexit 1\n'
+  )
+  await chmod(shim, 0o755)
+  process.env.PATH = `${shimDir}:${originalPath}`
+}
+
+test(
+  'extracts tarballs without absolute paths in tar arguments',
+  { skip: process.platform === 'win32' },
+  async () => {
+    await forbidAbsolutePathsInTar()
+    let dir = await getNpmContent(
+      '.' as FilePath,
+      'nanoid' as DependencyName,
+      '5.1.5' as DependencyVersion
+    )
+    match(await readFile(join(dir, 'package.json'), 'utf8'), /"name": "nanoid"/)
+    equal(existsSync(join(dir, 'package.tgz')), false)
+  }
+)
+
+test(
+  'removes temporary directory when tar extraction fails',
+  { skip: process.platform === 'win32' },
+  async () => {
+    await makeTarFail()
+    let before = await readdir(tmpdir())
+    await rejects(
+      getNpmContent(
+        '.' as FilePath,
+        'nanoid' as DependencyName,
+        '5.1.5' as DependencyVersion
+      )
+    )
+    let after = await readdir(tmpdir())
+    let leaked = after.filter(
+      name => name.startsWith('multiocular-') && !before.includes(name)
+    )
+    deepEqual(leaked, [])
+  }
+)