Allow run::bind config to specify different destination

ci/test.py

@@ -582,6 +582,32 @@ def test_bad_bind_option(self):
         )
         self.assertIn("Error: bad option(s) 'bad-option' for bind", s)
 
+    def test_bind_dest(self):
+        temp_dir = tempfile.mkdtemp("-pyrex")
+        self.addCleanup(shutil.rmtree, temp_dir)
+
+        temp_file = os.path.join(temp_dir, "data")
+
+        conf = self.get_config()
+        conf["run"]["bind"] += " %s:/foo" % (temp_dir)
+        conf.write_conf()
+
+        self.assertPyrexContainerShellCommand("echo 123 > /foo/data")
+
+        with open(temp_file, "r") as f:
+            self.assertEqual(f.read(), "123\n")
+
+    def test_malformed_bind_dest(self):
+
+        b = "/src:/dst:illegal-token"
+
+        conf = self.get_config()
+        conf["run"]["bind"] += " %s" % b
+        conf.write_conf()
+
+        s = self.assertPyrexContainerShellCommand("true", capture=True, returncode=1)
+        self.assertIn("Error: too many colons in run.bind entry '%s'." % b, s)
+
     def test_bad_confversion(self):
         # Verify that a bad config is an error
         conf = self.get_config()

pyrex.py

@@ -59,6 +59,10 @@ def __init__(self, *args, **kwargs):
         self.optionxform = lambda option: option
 
 
+class ParsingError(Exception):
+    pass
+
+
 def read_default_config(keep_defaults):
     with open(os.path.join(PYREX_ROOT, "pyrex.ini"), "r") as f:
         line = f.read().replace("@CONFVERSION@", PYREX_CONFVERSION)
@@ -346,7 +350,23 @@ def parse_bind_options(bind):
             else:
                 bad_options.append(opt)
 
-    return bind, options, bad_options
+    if bad_options:
+        raise ParsingError(
+            "bad option(s) '%s' for bind %s" % (" ".join(bad_options), bind)
+        )
+
+    binds = bind.split(":")
+
+    if len(binds) > 2:
+        raise ParsingError("too many colons in run.bind entry '%s'." % bind)
+    elif len(binds) == 1:
+        src = bind
+        dst = bind
+    else:
+        src = binds[0]
+        dst = binds[1]
+
+    return src, dst, options
 
 
 def prep_container(
@@ -528,22 +548,23 @@ def prep_container(
         + extra_bind
     )
     for b in set(binds):
-        b, options, bad_options = parse_bind_options(b)
-        if bad_options:
-            print("Error: bad option(s) '%s' for bind %s" % (" ".join(bad_options), b))
+        try:
+            src, dst, options = parse_bind_options(b)
+        except ParsingError as e:
+            print("Error: %s" % e)
             return []
 
-        if not os.path.exists(b):
+        if not os.path.exists(src):
             if options.optional:
                 continue
-            print("Error: bind source path {b} does not exist".format(b=b))
+            print("Error: bind source path {src} does not exist".format(src=src))
             return []
 
         engine_args.extend(
             [
                 "--mount",
-                "type=bind,src={b},dst={b}{ro}".format(
-                    b=b, ro=",readonly" if options.readonly else ""
+                "type=bind,src={src},dst={dst}{ro}".format(
+                    src=src, dst=dst, ro=",readonly" if options.readonly else ""
                 ),
             ]
         )