Implement v2-debug checks for args, config, customizations, s3, and environment variables #9775

aemous · 2025-10-09T14:37:52Z

Description of changes:

Implemented runtime checks for the following breaking changes via --v2-debug:
- Usage of PYTHONUTF8 and PYTHONIOENCODING env vars unsupported in v2.
- S3 copies executed under aws s3 namespace may call additional APIs for multipart S3 copies
- Signer used for S3 request is Sigv2 (I expect it's very rare for customers to be using sigv2 and run into this)
- [!] aws cloudformation deploy will not fail on empty changesets.
- Timestamps in responses will be formatted in ISO 8601.
- Usage of file:// with blob-type parameters.
- us-east-1 will use the regional endpoint in v2 rather than global.
- Usage of api_versions in config will not be supported in v2.
- Support for [plugins] will be provisional in v2.
- Pagination params used in --cli-input-json will disable automatic paging in v2.
Line-length formatting of other --v2-debug code.
Added tests to cover some added functionality

Description of tests:

Ran and passed all new tests.
Manually tested the file encoding checker by supplying PYTHONUTF8:

$ PYTHONUTF8=1 python3 -m awscli s3 ls --v2-debug
AWS CLI v2 MIGRATION WARNING: The PYTHONUTF8 and PYTHONIOENCODING environment variables are unsupported in AWS CLI v2. AWS CLI v2 uses AWS_CLI_FILE_ENCODING instead, set this environment variable to resolve this. See https://docs.aws.amazon.com/cli/latest/userguide/cliv2-migration-changes.html#cliv2-migration-encodingenvvar.

An error occurred (ExpiredToken) when calling the ListBuckets operation: The provided token has expired.

Manually tested the s3 copies checker via aws s3 cp:

$ python3 -m awscli s3 cp s3://BUCKET1/file1 s3://BUCKET2 --v2-debug
AWS CLI v2 MIGRATION WARNING: In AWS CLI v2, object properties will be copied from the source in multipart copies between S3 buckets. This may result in extra S3 API calls being made. Breakage may occur if the principal does not have permission to call these extra APIs. This warning cannot be resolved. See https://docs.aws.amazon.com/cli/latest/userguide/cliv2-migration-changes.html#cliv2-migration-s3-copy-metadata

copy: s3://BUCKET1/file1 to s3://BUCKET2

Manually tested the timestamps checker via aws s3 ls:

AWS CLI v2 MIGRATION WARNING: In AWS CLI v2, all timestamp response values are returned in the ISO 8601 format. To migrate to v2 behavior and resolve this warning, set the configuration variable `cli_timestamp_format` to `iso8601`. See https://docs.aws.amazon.com/cli/latest/userguide/cliv2-migration-changes.html#cliv2-migration-timestamp.
[...]

Manually tested specifying pagination params through --cli-input-json:

 $ aws s3api list-buckets --v2-debug --cli-input-json file://pagination-params.json 
AWS CLI v2 MIGRATION WARNING: In AWS CLI v2, if you specify pagination parameters by using a file with the `--cli-input-json` parameter, automatic pagination will be turned off. This is not the case in v1. See https://docs.aws.amazon.com/cli/latest/userguide/cliv2-migration-changes.html#cliv2-migration-skeleton-paging.
[...]

Manually tested specifying api_versions in config file:

api_versions =
    ec2 = 2016-11-15
    s3 = 2006-03-01

$ aws s3 ls --v2-debug
AWS CLI v2 MIGRATION WARNING: The AWS CLI v2 does not support calling earlier versions of AWS service APIs via the `api_versions` configuration file setting. To migrate to v2 behavior and resolve this warning, remove the `api_versions` setting in the configuration file. See https://docs.aws.amazon.com/cli/latest/userguide/cliv2-migration-changes.html#cliv2-migration-api-versions.

Manually tested using file:// for a blob-type parameter:

$ python3 -m awscli secretsmanager update-secret --secret-id SECRET-NAME --secret-binary file://BINARY-SECRET.json --v2-debug
AWS CLI v2 MIGRATION WARNING: When specifying a blob-type parameter starting with `file://`, AWS CLI v2 will assume the content of the file is already base64-encoded. To maintain v1 behavior after upgrading to v2, set the `cli_binary_format` configuration variable to `raw-in-base64-out`. See https://docs.aws.amazon.com/cli/latest/userguide/cliv2-migration-changes.html#cliv2-migration-binaryparam.
{
    "ARN": "ARN",
    "Name": "SECRET-NAME",
    "VersionId": "VERSION-ID"
}

After setting cli_binary_format to raw-in-base64-out, I've verified that the warning above was not printed.

Manually tested configuring region to us-east-1 and executing an S3 command:

$ python3 -m awscli s3 ls --v2-debug 
AWS CLI v2 MIGRATION WARNING: When you configure AWS CLI v2 to use the `us-east-1` region, it uses the true regional endpoint rather than the global endpoint. To continue using the global endpoint on v2, configure the region to be `aws-global`. See https://docs.aws.amazon.com/cli/latest/userguide/cliv2-migration-changes.html#cliv2-migration-s3-regional-endpoint.

After setting region to aws-global, I've verified that the warning above was not printed.

By submitting this pull request, I confirm that you can use, modify, copy, and redistribute this contribution, under the terms of your choice.

…config

codecov-commenter · 2025-10-09T16:14:28Z

Codecov Report

❌ Patch coverage is 83.95062% with 13 lines in your changes missing coverage. Please review.
⚠️ Please upload report for BASE (debug-migration@1fee97f). Learn more about missing BASE report.

Files with missing lines	Patch %	Lines
awscli/customizations/globalargs.py	78.12%	7 Missing ⚠️
awscli/customizations/scalarparse.py	66.66%	4 Missing ⚠️
awscli/clidriver.py	90.00%	1 Missing ⚠️
awscli/customizations/cloudformation/deploy.py	66.66%	1 Missing ⚠️

Additional details and impacted files

@@                Coverage Diff                 @@
##             debug-migration    #9775   +/-   ##
==================================================
  Coverage                   ?   93.28%           
==================================================
  Files                      ?      209           
  Lines                      ?    16885           
  Branches                   ?        0           
==================================================
  Hits                       ?    15752           
  Misses                     ?     1133           
  Partials                   ?        0

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ashovlin · 2025-10-14T13:44:58Z

awscli/customizations/s3/subcommands.py

        return sync_strategies

-    def run(self):
+    def run(self, v2_debug=False):


Could this go through self.parameters instead? That looks like where we're handling other info from parsed_globals.

ashovlin · 2025-10-14T14:05:25Z

awscli/customizations/scalarparse.py

+        encountered_timestamp = False
+        def identity_with_warning(x):
+            nonlocal encountered_timestamp
+            if not encountered_timestamp:
+                encountered_timestamp = True


Can you explain this flow better in comments? Is it so we're only printing a single warning per response?

Yes, without adding these guards I was getting flooded with messages (one per timestamp in the responses), which nearly made the feature unusable.

I'll update with comments

ashovlin · 2025-10-14T14:26:20Z

awscli/customizations/paginate.py

+# This function checks for pagination args in the actual calling
+# arguments passed to the function.  If the user is using the
+# --cli-input-json parameter to provide JSON parameters they are
+# all in the API naming space rather than the CLI naming space
+# and would be missed by the processing above.  This function gets
+# called on the calling-command event.


Generally prefer docstrings throughout. Though we don't generate user-facing docs from these, they're more helpful in IDEs for us and contributors.

ashovlin · 2025-10-14T14:31:53Z

awscli/customizations/globalargs.py

+    # The regional us-east-1 endpoint is used in certain cases (e.g.
+    # FIPS/Dual-Stack is enabled). Rather than duplicating this logic
+    # from botocore, we check the endpoint URL directly.


Is this why we need the actual endpoint check in addition to the us_east_1_regional_endpoint + us-east-1 logic above?

ashovlin · 2025-10-14T14:33:35Z

awscli/clidriver.py

        parser = ArgTableArgParser(arg_table)
        return parser

+    def _detect_migration_breakage(self, session, parsed_args, parsed_globals, arg_table):


If this is only dealing with the file://, then I think it'd be good to add that to the method name. I wouldn't want someone else to add logic that gets skipped by the early return.

ashovlin · 2025-10-14T14:34:07Z

awscli/customizations/globalargs.py

    _resolve_timeout(session, parsed_args, arg_name)

 def detect_migration_breakage(parsed_args, remaining_args, session, **kwargs):
    if parsed_args.v2_debug:


Given how long this got, it'd be nice to return early here if the mode isn't enabled to save an indent level.

ashovlin · 2025-10-14T14:37:49Z

awscli/customizations/paginate.py

+        pagination_params_in_input_tokens = [
+            param for param in call_parameters if param in input_tokens
+        ]


How is this limited to --cli-input-json?

Good point! Did some testing and it actually prints the warning even when its specified on the command directly. I'll need to fix this to maybe check what params came from cli-input-json and access them in paginate.py.

Will address in next revision

aemous added 12 commits October 8, 2025 11:44

Implement s3 and env vars v2-debug checks with tests.

aa0059e

Implement v2-debug runtime checks for customizations.

b1e4f12

Fix bug with s3 tests.

4145b1c

Implement checks for api_versions in config and plugins.

f1196fb

Fix s3 tests.

fab0005

Fix failing tests.

7d42580

Implement S3 us-east-1 global endpoint behavior.

9f336ca

Finish implementing cli-input-json and other use cases.

408023a

Ensure timestamp warning only prints at most once.

d77948a

Add test to s3 v2-debug.

a9599d2

Merge branch 'debug-migration-s3-env-vars' into debug-migration-args-…

427325a

…config

Formatting.

efb76f6

aemous requested a review from a team October 9, 2025 14:37

aemous added 2 commits October 9, 2025 10:51

Add test-input-json paginate test and format.

64c0d77

Test fixes.

6999974

aemous added 6 commits October 9, 2025 12:58

Fix opt-out case of cli_binary_format warning.

ccc918f

Fix failing unit tests in test_clidriver.

8d074f3

Update s3 us-east-1 behavior.

5ff72bc

Formatting.

1f322d6

Switch migration warnings to use stderr.

f75c3af

Fix failing s3 test.

df5fec0

ashovlin reviewed Oct 14, 2025

View reviewed changes

Revise based on feedback.

73a8347

aemous requested a review from ashovlin October 14, 2025 18:49

Fix failing s3 tests.

4411c1c

Provide feedback

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