fix extractTar on Windows (#264)

packages/tool-cache/__tests__/tool-cache.test.ts

@@ -268,7 +268,8 @@ describe('@actions/tool-cache', function() {
         await io.rmRF(tempDir)
       }
     })
-  } else {
+  }
+
   it('extract .tar.gz', async () => {
     const tempDir = path.join(tempPath, 'test-install-tar.gz')
 
@@ -293,10 +294,7 @@ describe('@actions/tool-cache', function() {
       fs.existsSync(path.join(toolPath, 'folder', 'nested-file.txt'))
     ).toBeTruthy()
     expect(
-        fs.readFileSync(
-          path.join(toolPath, 'folder', 'nested-file.txt'),
-          'utf8'
-        )
+      fs.readFileSync(path.join(toolPath, 'folder', 'nested-file.txt'), 'utf8')
     ).toBe('folder/nested-file.txt contents')
   })
 
@@ -326,10 +324,7 @@ describe('@actions/tool-cache', function() {
       fs.existsSync(path.join(toolPath, 'folder', 'nested-file.txt'))
     ).toBeTruthy()
     expect(
-        fs.readFileSync(
-          path.join(toolPath, 'folder', 'nested-file.txt'),
-          'utf8'
-        )
+      fs.readFileSync(path.join(toolPath, 'folder', 'nested-file.txt'), 'utf8')
     ).toBe('folder/nested-file.txt contents')
   })
 
@@ -350,14 +345,11 @@ describe('@actions/tool-cache', function() {
     expect(fs.existsSync(toolPath)).toBeTruthy()
     expect(fs.existsSync(`${toolPath}.complete`)).toBeTruthy()
     expect(fs.existsSync(path.join(toolPath, 'bar.txt'))).toBeTruthy()
-      expect(
-        fs.existsSync(path.join(toolPath, 'foo', 'hello.txt'))
-      ).toBeTruthy()
+    expect(fs.existsSync(path.join(toolPath, 'foo', 'hello.txt'))).toBeTruthy()
     expect(
       fs.readFileSync(path.join(toolPath, 'foo', 'hello.txt'), 'utf8')
     ).toBe('foo/hello: world')
   })
-  }
 
   it('installs a zip and finds it', async () => {
     const tempDir = path.join(__dirname, 'test-install-zip')

packages/tool-cache/src/tool-cache.ts

@@ -202,9 +202,41 @@ export async function extractTar(
     throw new Error("parameter 'file' is required")
   }
 
+  // Create dest
   dest = await _createExtractFolder(dest)
-  const tarPath: string = await io.which('tar', true)
-  await exec(`"${tarPath}"`, [flags, '-C', dest, '-f', file])
+
+  // Determine whether GNU tar
+  let versionOutput = ''
+  await exec('tar --version', [], {
+    ignoreReturnCode: true,
+    listeners: {
+      stdout: (data: Buffer) => (versionOutput += data.toString()),
+      stderr: (data: Buffer) => (versionOutput += data.toString())
+    }
+  })
+  const isGnuTar = versionOutput.toUpperCase().includes('GNU TAR')
+
+  // Initialize args
+  const args = [flags]
+
+  let destArg = dest
+  let fileArg = file
+  if (IS_WINDOWS && isGnuTar) {
+    args.push('--force-local')
+    destArg = dest.replace(/\\/g, '/')
+
+    // Technically only the dest needs to have `/` but for aesthetic consistency
+    // convert slashes in the file arg too.
+    fileArg = file.replace(/\\/g, '/')
+  }
+
+  if (isGnuTar) {
+    // Suppress warnings when using GNU tar to extract archives created by BSD tar
+    args.push('--warning=no-unknown-keyword')
+  }
+
+  args.push('-C', destArg, '-f', fileArg)
+  await exec(`tar`, args)
 
   return dest
 }