fix: argo 3.7.11 conditional input paths

[saikonen]

PR Type

• Bug fix

Summary

Fixes an issue with step input-paths from conditionals not working on argo 3.7.11+/4.0.2+

Issue

Fixes #3043

AI Tool Usage

Claude Code used for test cases and fix iteration

[greptile-apps]

Greptile Summary

The PR updates Argo conditional execution so skipped branches expose resolvable outputs and downstream tasks include only predecessors that actually ran.

• Adds Steps wrappers and should-run outputs for conditional nodes.
• Reworks dependency, when, and input-path expressions for nested and sequential conditionals.
• Filters Argo’s SKIPPED sentinel from conditional input paths.
• Adds regression coverage and updates the local Argo environment to v3.7.11.

Confidence Score: 5/5

The PR appears safe to merge because no blocking failure remains within the eligible follow-up review scope.

No blocking failure remains.

Important Files Changed

Filename	Overview
metaflow/plugins/argo/argo_workflows.py	Introduces conditional Steps wrappers, stable skipped-branch outputs, and revised dependency and input-path generation for newer Argo releases.
metaflow/plugins/argo/conditional_input_paths.py	Excludes the explicit /SKIPPED sentinel when selecting executed predecessor pathspecs.
test/unit/test_argo_conditional_input_paths.py	Adds focused coverage for skipped sentinels and fallback path selection.
test/unit/test_argo_nested_conditional_join.py	Expands regression coverage for nested, sequential, and recursive conditional gating.
devtools/Tiltfile	Updates the local Argo chart and controller defaults to exercise Argo Workflows v3.7.11.

_{Reviews (3): Last reviewed commit: "fix: exclude foreach joins from wrapped_..." | Re-trigger Greptile}

[Shriprasad-P]

Review

PR: fix: argo 3.7.11 conditional input paths

Touched: devtools/Tiltfile, metaflow/plugins/argo/argo_workflows.py, metaflow/plugins/argo/conditional_input_paths.py, test/unit/test_argo_conditional_input_paths.py, test/unit/test_argo_nested_conditional_join.py

• Addresses a concrete correctness/reliability issue based on the title and diff.
• CI/tooling change — confirm the pipeline still passes on this branch.
• Diff is fairly large (+632/-156); a short summary of risk areas from the author would help reviewers.

Commenting as a drive-by reviewer after reading the diff. Happy to look again if maintainers want a deeper pass on a specific file.

[Gsbreddy]

Wanted to share some field validation for this fix.

We (Delivery Hero, running Metaflow on Argo Workflows at scale) hit exactly the issue this PR fixes (#3043) while validating an Argo Workflows v3.7.11→v4.1.4 upgrade. We reproduced the conditional-branch failure cleanly on both v3.7.15 and v4.1.4 (unable to substitute {{tasks.X.outputs...}}: output is an absent optional), then pinned our Metaflow install to this branch's commit (326d90a) and re-ran the same repro on both versions — conditional branching now completes successfully on both, with the new cond- wrapped Steps templates showing up as expected in the compiled DAG.

This is a real blocker for anyone upgrading past Argo Workflows v3.7.11/v4.0.2, so it'd be great to see this land.