Merge ~ack/maas:1951398-cli-encode-as-file-3.1 into maas:3.1

[Alberto Donato]

LP:1951398 keep @= parameters as uploaded files for POST actions

When @= is used in the CLI to read a parameter from file, only read the content
directly if the action is GET or DELETE, otherwise pass it as a file, so that
it gets multipart-encoded correctly (the filename= parameter is set in the
Content-Disposition header).

[MAAS Lander (maas-lander)]

UNIT TESTS
-b 1951398-cli-encode-as-file-3.1 lp:~ack/maas/+git/maas into -b 3.1 lp:~maas-committers/maas

STATUS: SUCCESS
COMMIT: f1e792df727eb623cca45544b2ba3a05b90a62c9

review: Approve

[Alberto Donato (ack)]

review: Approve

diff --git a/src/maascli/api.py b/src/maascli/api.py
index a82f5c7..c533f1f 100644
--- a/src/maascli/api.py
+++ b/src/maascli/api.py
@@ -198,7 +198,7 @@ class Action(Command):
             if what == "=":
                 return name, value
             elif what == "@=":
-                return name, partial(open, value)
+                return name, partial(open, value, "rb")
             else:
                 raise AssertionError("Unrecognised separator %r" % what)
         else:
@@ -222,25 +222,26 @@ class Action(Command):
             tuples (see `name_value_pair`) to pack into the body or
             query, depending on the type of request.
         """
-        params_in_qs = method in ("GET", "DELETE")
         query = [("op", op)] if op else []
 
+        headers, body = [], None
+
         def slurp(opener):
-            with opener("r" if params_in_qs else "rb") as fd:
+            with opener() as fd:
                 return fd.read()
 
-        # read content for file-based parameters
-        data = [
-            (key, slurp(value) if callable(value) else value)
-            for key, value in data
-        ]
-
-        headers, body = [], None
-        if params_in_qs:
-            query.extend(data)
-        elif data:
-            message = build_multipart_message(data)
-            headers, body = encode_multipart_message(message)
+        if method in ("GET", "DELETE"):
+            query.extend(
+                (name, slurp(value) if callable(value) else value)
+                for name, value in data
+            )
+            body, headers = None, []
+        else:
+            if data is None or len(data) == 0:
+                body, headers = None, []
+            else:
+                message = build_multipart_message(data)
+                headers, body = encode_multipart_message(message)
 
         uri = urlparse(uri)._replace(query=urlencode(query)).geturl()
         return uri, body, headers
diff --git a/src/maascli/tests/test_api.py b/src/maascli/tests/test_api.py
index 402bdc2..12ae2c3 100644
--- a/src/maascli/tests/test_api.py
+++ b/src/maascli/tests/test_api.py
@@ -2,6 +2,7 @@
 # GNU Affero General Public License version 3 (see the file LICENSE).
 
 from base64 import b64encode
+from functools import partial
 import http.client
 import json
 import sys
@@ -698,7 +699,7 @@ class TestPayloadPreparationWithFiles:
         # command-line causes name_value_pair() to return a `name,
         # opener` tuple, where `opener` is a callable that returns an
         # open file handle.
-        data = [(parameter, payload_file.open)]
+        data = [(parameter, partial(payload_file.open, "rb"))]
         return parameter, contents, data
 
     @pytest.mark.parametrize("op", [None, "action"])
@@ -718,7 +719,7 @@ class TestPayloadPreparationWithFiles:
             "Content-Type: application/octet-stream",
             "MIME-Version: 1.0",
             "Content-Transfer-Encoding: base64",
-            f'Content-Disposition: form-data; name="{parameter}"',
+            f'Content-Disposition: form-data; name="{parameter}"; filename="{parameter}"',
             b64encode(contents).decode("ascii"),
         ]
         for line in content_lines: