Create setup and initial runtime checkers

.changes/next-release/enhancement-Migration-48043.json

@@ -0,0 +1,5 @@
+{
+  "type": "enhancement",
+  "category": "Migration",
+  "description": "Implement a ``--migrate-v2`` flag that detects breaking changes for AWS CLI v2 for entered commands."
+}

awscli/clidriver.py

@@ -79,6 +79,7 @@ def main():
 def create_clidriver():
     session = botocore.session.Session(EnvironmentVariables)
     _set_user_agent_for_session(session)
+    # TODO check if full config plugins is empty or not. if it's not, we signal the warning for plugin support being provisional
     load_plugins(
         session.full_config.get('plugins', {}),
         event_hooks=session.get_component('event_emitter'),
@@ -225,7 +226,7 @@ def main(self, args=None):
             # that exceptions can be raised, which should have the same
             # general exception handling logic as calling into the
             # command table.  This is why it's in the try/except clause.
-            self._handle_top_level_args(parsed_args)
+            self._handle_top_level_args(parsed_args, remaining)
             self._emit_session_event(parsed_args)
             HISTORY_RECORDER.record(
                 'CLI_VERSION', self.session.user_agent(), 'CLI'
@@ -279,8 +280,8 @@ def _show_error(self, msg):
         sys.stderr.write(msg)
         sys.stderr.write('\n')
 
-    def _handle_top_level_args(self, args):
-        emit_top_level_args_parsed_event(self.session, args)
+    def _handle_top_level_args(self, args, remaining):
+        emit_top_level_args_parsed_event(self.session, args, remaining, self._get_argument_table())
         if args.profile:
             self.session.set_config_variable('profile', args.profile)
         if args.region:

awscli/customizations/cloudformation/deploy.py

@@ -339,6 +339,9 @@ def deploy(self, deployer, stack_name, template_str,
                 tags=tags
             )
         except exceptions.ChangeEmptyError as ex:
+            # TODO print the runtime check for cli v2 breakage. technically won't be breaking if --fail-on-empty-changeset is
+            # explicitly provided. but we cannot differentiate between whether fail-on-empty-changeset is true because it's default
+            # or because it's explicitly specified.
             if fail_on_empty_changeset:
                 raise
             write_exception(ex, outfile=get_stdout_text_writer())

awscli/customizations/globalargs.py

@@ -12,6 +12,9 @@
 # language governing permissions and limitations under the License.
 import sys
 import os
+
+from awscli.customizations.argrename import HIDDEN_ALIASES
+from awscli.customizations.utils import uni_print
 from botocore.client import Config
 from botocore import UNSIGNED
 from botocore.endpoint import DEFAULT_TIMEOUT
@@ -30,6 +33,8 @@ def register_parse_global_args(cli):
                  unique_id='resolve-cli-read-timeout')
     cli.register('top-level-args-parsed', resolve_cli_connect_timeout,
                  unique_id='resolve-cli-connect-timeout')
+    cli.register('top-level-args-parsed', detect_migration_breakage,
+                 unique_id='detect-migration-breakage')
 
 
 def resolve_types(parsed_args, **kwargs):
@@ -90,6 +95,21 @@ def resolve_cli_connect_timeout(parsed_args, session, **kwargs):
     arg_name = 'connect_timeout'
     _resolve_timeout(session, parsed_args, arg_name)
 
+def detect_migration_breakage(parsed_args, remaining_args, argument_table, session, **kwargs):
+    if parsed_args.migrate_v2:
+        url_params = [param for param in remaining_args if param.startswith('http://') or param.startswith('https://')]
+        uni_print("AWS CLI v2 MIGRATION WARNING: By default, AWS CLI v2 returns all output through your operating system’s default pager program. See https://docs.aws.amazon.com/cli/latest/userguide/cliv2-migration-changes.html#cliv2-migration-output-pager.\n")
+        if parsed_args.command == 'ecr' and remaining_args[0] == 'get-login':
+            uni_print('AWS CLI v2 MIGRATION WARNING: The ecr get-login command has been removed in AWS CLI v2. See https://docs.aws.amazon.com/cli/latest/userguide/cliv2-migration-changes.html#cliv2-migration-ecr-get-login.\n')
+        if url_params:
+            uni_print('AWS CLI v2 MIGRATION WARNING: For input parameters that have a prefix of http:// or https://, AWS CLI v2 will no longer automatically request the content of the URL for the parameter, and the cli_follow_urlparam option has been removed. See https://docs.aws.amazon.com/cli/latest/userguide/cliv2-migration-changes.html#cliv2-migration-paramfile.\n')
+        for working, obsolete in HIDDEN_ALIASES.items():
+            working_split = working.split('.')
+            working_service = working_split[0]
+            working_cmd = working_split[1]
+            working_param = working_split[2]
+            if parsed_args.command == working_service and remaining_args[0] == working_cmd and f"--{working_param}" in remaining_args:
+                uni_print('AWS CLI v2 MIGRATION WARNING: You have entered command arguments that uses at least 1 of 21 hidden aliases that were removed in AWS CLI v2. See https://docs.aws.amazon.com/cli/latest/userguide/cliv2-migration-changes.html#cliv2-migration-aliases.\n')
 
 def resolve_cli_read_timeout(parsed_args, session, **kwargs):
     arg_name = 'read_timeout'

awscli/customizations/scalarparse.py

@@ -64,6 +64,7 @@ def add_timestamp_parser(session):
         # parser (which parses to a datetime.datetime object) with the
         # identity function which prints the date exactly the same as it comes
         # across the wire.
+        # TODO create an inner function that wraps identity here. it'll signal to print the runtime check.
         timestamp_parser = identity
     elif timestamp_format == 'iso8601':
         timestamp_parser = iso_format

awscli/data/cli.json

@@ -64,6 +64,11 @@
             "dest": "connect_timeout",
             "type": "int",
             "help": "<p>The maximum socket connect time in seconds. If the value is set to 0, the socket connect will be blocking and not timeout. The default value is 60 seconds.</p>"
+        },
+        "migrate-v2": {
+            "action": "store_true",
+            "dest": "migrate_v2",
+            "help": "<p>Enable AWS CLI v2 migration assistance. Prints warnings if the command would face a breaking change after swapping AWS CLI v1 for AWS CLI v2 in the current environment. Prints one warning for each breaking change detected.</p>"
         }
     }
 }

awscli/examples/global_options.rst

@@ -70,3 +70,7 @@
 
   The maximum socket connect time in seconds. If the value is set to 0, the socket connect will be blocking and not timeout. The default value is 60 seconds.
 
+``--migrate-v2`` (boolean)
+
+  Enable AWS CLI v2 migration assistance. Prints warnings if the command would face a breaking change after swapping AWS CLI v1 for AWS CLI v2 in the current environment. Prints one warning for each breaking change detected.
+

awscli/examples/global_synopsis.rst

@@ -12,3 +12,4 @@
 [--ca-bundle <value>]
 [--cli-read-timeout <value>]
 [--cli-connect-timeout <value>]
+[--migrate-v2]

awscli/utils.py

@@ -205,8 +205,14 @@ def ignore_ctrl_c():
         signal.signal(signal.SIGINT, original)
 
 
-def emit_top_level_args_parsed_event(session, args):
-    session.emit('top-level-args-parsed', parsed_args=args, session=session)
+def emit_top_level_args_parsed_event(session, args, remaining, argument_table):
+    session.emit(
+        'top-level-args-parsed',
+        parsed_args=args,
+        remaining_args=remaining,
+        argument_table=argument_table,
+        session=session
+    )
 
 
 def is_a_tty():

tests/unit/test_clidriver.py

@@ -91,6 +91,11 @@
             "connect-timeout": {
                 "type": "int",
                 "help": ""
+            },
+            "migrate-v2": {
+                "action": "store_true",
+                "dest": "migrate_v2",
+                "help": "",
             }
         }
     },