Provide better error message on missing commands

Before running a command in the sandbox, check its existence and fail
early if it does not.

This fixes issue #289.

6 files changed, 54 insertions, 0 deletions

diff --git a/buildstream/sandbox/_sandboxbwrap.py b/buildstream/sandbox/_sandboxbwrap.py
index 3a0645aae..9ed677620 100644
--- a/buildstream/sandbox/_sandboxbwrap.py
+++ b/buildstream/sandbox/_sandboxbwrap.py
@@ -28,6 +28,7 @@ from contextlib import ExitStack
 
 import psutil
 
+from .._exceptions import SandboxError
 from .. import utils, _signals
 from ._mount import MountMap
 from . import Sandbox, SandboxFlags
@@ -66,6 +67,11 @@ class SandboxBwrap(Sandbox):
         if env is None:
             env = self._get_environment()
 
+        if not self._has_command(command[0], env):
+            raise SandboxError("Staged artifacts do not provide command "
+                               "'{}'".format(command[0]),
+                               reason='missing-command')
+
         # We want command args as a list of strings
         if isinstance(command, str):
             command = [command]
diff --git a/buildstream/sandbox/_sandboxchroot.py b/buildstream/sandbox/_sandboxchroot.py
index 22e69d549..8788c3031 100644
--- a/buildstream/sandbox/_sandboxchroot.py
+++ b/buildstream/sandbox/_sandboxchroot.py
@@ -58,6 +58,11 @@ class SandboxChroot(Sandbox):
         if env is None:
             env = self._get_environment()
 
+        if not self._has_command(command[0], env):
+            raise SandboxError("Staged artifacts do not provide command "
+                               "'{}'".format(command[0]),
+                               reason='missing-command')
+
         # Command must be a list
         if isinstance(command, str):
             command = [command]
diff --git a/buildstream/sandbox/sandbox.py b/buildstream/sandbox/sandbox.py
index 595b9e778..7e1e32b65 100644
--- a/buildstream/sandbox/sandbox.py
+++ b/buildstream/sandbox/sandbox.py
@@ -279,3 +279,25 @@ class Sandbox():
     #              data passed in during construction.
     def _get_config(self):
         return self.__config
+
+    # _has_command()
+    #
+    #  Tests whether a command exists inside the sandbox
+    #
+    #     Args:
+    #         command (list): The command to test.
+    #         env (dict): A dictionary of string key, value pairs to set as environment
+    #                     variables inside the sandbox environment.
+    #     Returns:
+    #         (bool): Whether a command exists inside the sandbox.
+    def _has_command(self, command, env=None):
+        if os.path.isabs(command):
+            return os.path.exists(os.path.join(
+                self.get_directory(), command.lstrip(os.sep)))
+
+        for path in env.get('PATH').split(':'):
+            if os.path.exists(os.path.join(
+                    self.get_directory(), path.lstrip(os.sep), command)):
+                return True
+
+        return False
diff --git a/tests/sandboxes/missing-command.py b/tests/sandboxes/missing-command.py
new file mode 100644
index 000000000..8f210bcec
--- /dev/null
+++ b/tests/sandboxes/missing-command.py
@@ -0,0 +1,19 @@
+import os
+import pytest
+
+from buildstream._exceptions import ErrorDomain
+
+from tests.testutils import cli
+
+
+DATA_DIR = os.path.join(
+    os.path.dirname(os.path.realpath(__file__)),
+    "missing-command"
+)
+
+
+@pytest.mark.datafiles(DATA_DIR)
+def test_missing_command(cli, tmpdir, datafiles):
+    project = os.path.join(datafiles.dirname, datafiles.basename)
+    result = cli.run(project=project, args=['build', 'no-runtime.bst'])
+    result.assert_task_error(ErrorDomain.SANDBOX, 'missing-command')
diff --git a/tests/sandboxes/missing-command/no-runtime.bst b/tests/sandboxes/missing-command/no-runtime.bst
new file mode 100644
index 000000000..4d7f70266
--- /dev/null
+++ b/tests/sandboxes/missing-command/no-runtime.bst
@@ -0,0 +1 @@
+kind: manual
diff --git a/tests/sandboxes/missing-command/project.conf b/tests/sandboxes/missing-command/project.conf
new file mode 100644
index 000000000..b32753625
--- /dev/null
+++ b/tests/sandboxes/missing-command/project.conf
@@ -0,0 +1 @@
+name: test