[test] Check for sftp-server for remote-run --debug-as-local tests (#18759)

Not all systems have sftp-server installed.

Author: jrose-apple

test/lit.cfg

@@ -941,7 +941,8 @@ ENV_VAR_PREFIXES = {
 }
 TARGET_ENV_PREFIX = ENV_VAR_PREFIXES.get(config.target_sdk_name, "")
 
-if not config.target_run and 'remote_run_host' in lit_config.params:
+if (not getattr(config, 'target_run', None) and
+    'remote_run_host' in lit_config.params):
     if 'remote_run_tmpdir' not in lit_config.params:
         lit_config.fatal("'remote_run_host' provided, but no "
                          "'remote_run_tmpdir'")
@@ -1039,6 +1040,21 @@ base_runtime_lib_name = (
 if os.path.exists(make_path(compiler_rt_dir, base_runtime_lib_name)):
     config.available_features.add('c_runtime')
 
+# For testing the remote-run utility itself, see if we can find an sftp-server
+# binary.
+def find_sftp_server():
+    paths_to_try = ['/usr/libexec/sftp-server', '/usr/lib/sftp-server',
+                    '/usr/libexec/openssh/sftp-server',
+                    '/usr/lib/openssh/sftp-server']
+    return next((path for path in paths_to_try if os.path.isfile(path)), None)
+
+sftp_server_path = find_sftp_server()
+if sftp_server_path:
+    config.available_features.add('sftp_server')
+config.substitutions.append(('%sftp-server',
+                             sftp_server_path or 'no-sftp-server'))
+
+
 if not getattr(config, 'target_run_simple_swift', None):
     config.target_run_simple_swift = (
         '%%empty-directory(%%t) && '

test/remote-run/download.test-sh

@@ -1,3 +1,5 @@
+REQUIRES: sftp_server
+
 RUN: %empty-directory(%t)
 RUN: %empty-directory(%t-REMOTE)
 RUN: %debug-remote-run --output-prefix %t touch %t/output

test/remote-run/lit.local.cfg

@@ -2,4 +2,4 @@
 config.substitutions = list(config.substitutions)
 
 config.substitutions.insert(0, ('%debug-remote-run',
-  '%utils/remote-run --debug-as-local --remote-dir %t-REMOTE') )
+  '%utils/remote-run --debug-as-local %sftp-server --remote-dir %t-REMOTE') )

test/remote-run/upload-and-download.test-sh

@@ -1,3 +1,5 @@
+REQUIRES: sftp_server
+
 RUN: %empty-directory(%t)
 RUN: %empty-directory(%t-REMOTE)
 RUN: touch %t/input %t/BAD

test/remote-run/upload-stderr.test-sh

@@ -1,3 +1,5 @@
+REQUIRES: sftp_server
+
 RUN: %empty-directory(%t)
 RUN: %empty-directory(%t/REMOTE/input)
 RUN: chmod a-w %t/REMOTE/input

test/remote-run/upload.test-sh

@@ -1,3 +1,5 @@
+REQUIRES: sftp_server
+
 RUN: %debug-remote-run --input-prefix %S/Inputs/upload/ ls %S/Inputs/upload/1.txt %S/Inputs/upload/2.txt | %FileCheck -check-prefix CHECK-REMOTE %s
 RUN: ls %t-REMOTE/input/ | %FileCheck %s
 

utils/remote-run

@@ -119,22 +119,14 @@ class RemoteCommandRunner(CommandRunner):
                 [self.remote_host])
 
 class LocalCommandRunner(CommandRunner):
-    def __init__(self):
-        self.cached_sftp_server_path = None
-
-    def sftp_server_path(self):
-        if not self.cached_sftp_server_path:
-            paths_to_try = ['/usr/libexec/sftp-server', '/usr/lib/sftp-server']
-            self.cached_sftp_server_path = next(
-                (path for path in paths_to_try if os.path.exists(path)),
-                paths_to_try[0])
-        return self.cached_sftp_server_path
+    def __init__(self, sftp_server_path):
+        self.sftp_server_path = sftp_server_path
 
     def remote_invocation(self, command):
         return command
 
     def sftp_invocation(self):
-        return ['/usr/bin/sftp', '-b', '-', '-q', '-D', self.sftp_server_path()]
+        return ['/usr/bin/sftp', '-b', '-', '-q', '-D', self.sftp_server_path]
 
 def find_transfers(args, source_prefix, dest_prefix):
     if source_prefix.endswith(os.path.sep):
@@ -172,7 +164,7 @@ def main():
 
     parser.add_argument('-i', '--identity', dest='identity', metavar='FILE',
                         help='an SSH identity file (private key) to use')
-    parser.add_argument('--debug-as-local', action='store_true',
+    parser.add_argument('--debug-as-local', metavar='/PATH/TO/SFTP-SERVER',
                         help='run commands locally instead of over SSH, for '
                              'debugging purposes. The "host" argument is '
                              'omitted.')
@@ -185,7 +177,7 @@ def main():
     args = parser.parse_args()
 
     if args.debug_as_local:
-        runner = LocalCommandRunner()
+        runner = LocalCommandRunner(args.debug_as_local)
         args.command.insert(0, args.host)
         del args.host
     else: