scripts: runners: abstract jlink's missing program support

The runners/jlink.py script has a mechanism for erroring out if a host
tool is not installed. Abstract it into runners/core.py and handle it
from run_common.py. This will let it be used in more places.

Signed-off-by: Marti Bolivar <marti.bolivar@nordicsemi.no>

scripts/west_commands/run_common.py

@@ -17,7 +17,7 @@ from build_helpers import find_build_dir, is_zephyr_build, \
     FIND_BUILD_DIR_DESCRIPTION
 from west.commands import CommandContextError
 
-from runners import get_runner_cls, ZephyrBinaryRunner
+from runners import get_runner_cls, ZephyrBinaryRunner, MissingProgram
 
 from zephyr_ext_common import cached_runner_config
 
@@ -229,7 +229,11 @@ def do_run_common(command, args, runner_args, cached_runner_var):
     if unknown:
         log.die('Runner', runner, 'received unknown arguments:', unknown)
     runner = runner_cls.create(cfg, parsed_args)
-    runner.run(command_name)
+    try:
+        runner.run(command_name)
+    except MissingProgram as e:
+        log.die('required program', e.filename,
+                'not found; install it or add its location to PATH')
 
 
 #

scripts/west_commands/runners/__init__.py

@@ -2,7 +2,7 @@
 #
 # SPDX-License-Identifier: Apache-2.0
 
-from runners.core import ZephyrBinaryRunner
+from runners.core import ZephyrBinaryRunner, MissingProgram
 
 # We import these here to ensure the ZephyrBinaryRunner subclasses are
 # defined; otherwise, ZephyrBinaryRunner.create_for_shell_script()

scripts/west_commands/runners/core.py

@@ -13,8 +13,10 @@ as well as some other helpers for concrete runner classes.
 
 import abc
 import argparse
+import errno
 import os
 import platform
+import shutil
 import signal
 import subprocess
 
@@ -157,6 +159,19 @@ class BuildConfiguration:
             return value
 
 
+class MissingProgram(FileNotFoundError):
+    '''FileNotFoundError subclass for missing program dependencies.
+
+    No significant changes from the parent FileNotFoundError; this is
+    useful for explicitly signaling that the file in question is a
+    program that some class requires to proceed.
+
+    The filename attribute contains the missing program.'''
+
+    def __init__(self, program):
+        super().__init__(errno.ENOENT, os.strerror(errno.ENOENT), program)
+
+
 class RunnerCaps:
     '''This class represents a runner class's capabilities.
 
@@ -415,6 +430,20 @@ class ZephyrBinaryRunner(abc.ABC):
 
         In case of an unsupported command, raise a ValueError.'''
 
+    def require(self, program):
+        '''Require that a program is installed before proceeding.
+
+        :param program: name of the program that is required,
+                        or path to a program binary.
+
+        If ``program`` is an absolute path to an existing program
+        binary, this call succeeds. Otherwise, try to find the program
+        by name on the system PATH.
+
+        On error, raises MissingProgram.'''
+        if shutil.which(program) is None:
+            raise MissingProgram(program)
+
     def run_server_and_client(self, server, client):
         '''Run a server that ignores SIGINT, and a client that handles it.
 

scripts/west_commands/runners/jlink.py

@@ -107,10 +107,6 @@ class JLinkBinaryRunner(ZephyrBinaryRunner):
     def print_gdbserver_message(self):
         log.inf('J-Link GDB server running on port {}'.format(self.gdb_port))
 
-    def check_cmd(self, cmd):
-        if shutil.which(cmd) is None:
-            log.die('{} is not installed or cannot be found'.format(cmd))
-
     def do_run(self, command, **kwargs):
         server_cmd = ([self.gdbserver] +
                       ['-select', 'usb', # only USB connections supported
@@ -125,11 +121,11 @@ class JLinkBinaryRunner(ZephyrBinaryRunner):
         if command == 'flash':
             self.flash(**kwargs)
         elif command == 'debugserver':
-            self.check_cmd(self.gdbserver)
+            self.require(self.gdbserver)
             self.print_gdbserver_message()
             self.check_call(server_cmd)
         else:
-            self.check_cmd(self.gdbserver)
+            self.require(self.gdbserver)
             if self.gdb_cmd is None:
                 raise ValueError('Cannot debug; gdb is missing')
             if self.elf_name is None:
@@ -149,7 +145,7 @@ class JLinkBinaryRunner(ZephyrBinaryRunner):
             self.run_server_and_client(server_cmd, client_cmd)
 
     def flash(self, **kwargs):
-        self.check_cmd(self.commander)
+        self.require(self.commander)
         if self.bin_name is None:
             raise ValueError('Cannot flash; bin_name is missing')