Address #177 review comments: harden image-template formatting + base-image docs

[wyli]

Follow-up to #177 (merged), addressing its review comments.

Changes

container/core.py

• _format_image_template: parse the HOLOSCAN_CLI_*_IMAGE_FORMAT placeholders with string.Formatter and fatal() on unknown/missing fields or an invalid template, instead of letting a mistyped or unset placeholder raise a raw KeyError/ValueError traceback. Parsing the fields (rather than a substring check) also fixes "{sdk_version" in template misfiring on escaped {{sdk_version}}. — coderabbitai, Copilot
• default_base_image: compute cuda_tag lazily so the host GPU/driver probe (and its warning) no longer runs on the branches that return an explicit image or fatal() without using it. — Copilot

README.md

• Rewrite the base-image configuration section into three explicit methods (--base-img flag, fully-qualified HOLOSCAN_CLI_BASE_IMAGE, or repository + HOLOSCAN_CLI_BASE_SDK_VERSION). — agirault

tests

• New test_container_core.py cases for the _format_image_template validation paths and the no-host-probe fatal path in default_base_image.
• Clarifying comment in test_get_cuda_tag_handles_sdk_and_cuda_matrix explaining the stubbed host probes (why a None cuda_version resolves to an igpu tag). — tbirdso

Testing

• black --check + isort --check clean; pytest tests/unit green (the wheel-install console-script test requires an installed dist, unrelated to this change).

🤖 Generated with Claude Code

Summary by CodeRabbit

• Documentation

  • Clarified that holoscan-cli version alignment doesn't require matching Holoscan SDK runtime or container image
  • Expanded base image configuration guidance with multiple options: --base-img flag, HOLOSCAN_CLI_BASE_IMAGE environment variable, and dynamic CUDA version detection
  • Updated behavior to prompt for base image when unconfigured

• Bug Fixes

  • Enhanced validation for base image template configurations with explicit error messaging

[github-actions]

Dependency Review

✅ No vulnerabilities or license issues or OpenSSF Scorecard issues found.

Scanned Files

None

[coderabbitai]

No actionable comments were generated in the recent review. 🎉

ℹ️ Recent review info

⚙️ Run configuration

Configuration used: Organization UI

Review profile: CHILL

Plan: Pro

Run ID: 7eff6344-de2d-4f3c-a101-75236a4e3d70

📥 Commits

Reviewing files that changed from the base of the PR and between c0ce0e7 and 97378f4.

📒 Files selected for processing (4)

• README.md
• src/holoscan_cli/container/core.py
• tests/unit/test_container_core.py
• tests/unit/test_sdk_utils.py

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Walkthrough

The PR refactors base image template handling in the Holoscan CLI container module. It improves placeholder validation in image-template formatting, defers CUDA tag computation to only the paths requiring it, and updates documentation to clarify base image configuration options and fallback behavior.

Changes

Base image template and configuration

Layer / File(s)	Summary
Template formatting refactor with placeholder validation src/holoscan_cli/container/core.py, tests/unit/test_container_core.py	string.Formatter().parse() replaces substring-based placeholder checking, explicitly validating that referenced template fields exist and required values are provided; fatal errors raised for unknown fields, missing values, and invalid format operations.
Lazy CUDA tag evaluation in default_base_image src/holoscan_cli/container/core.py, tests/unit/test_container_core.py	cuda_tag computation via get_cuda_tag() shifts from eager evaluation at method entry to lazy computation only in the BASE_SDK_VERSION fallback path, avoiding unnecessary host probing when explicit base image is configured.
Documentation updates for base image configuration README.md, tests/unit/test_sdk_utils.py	README versioning section restructured to explain three base image configuration methods (flag, full image env var, env vars with dynamic CUDA tag derivation) and updated fallback prompt behavior; test comments clarify deterministic host stubs for CUDA resolution.

Estimated code review effort

🎯 3 (Moderate) | ⏱️ ~20 minutes

Possibly related PRs

• nvidia-holoscan/holoscan-cli#177: Modifies HoloscanContainer base-image and defaulting logic in the same file with overlapping changes to default_base_image behavior and corresponding unit test coverage.

Suggested reviewers

• tbirdso

🚥 Pre-merge checks | ✅ 4

✅ Passed checks (4 passed)

Check name	Status	Explanation
Description Check	✅ Passed	Check skipped - CodeRabbit’s high-level summary is enabled.
Title check	✅ Passed	The title accurately summarizes the main changes: addressing review comments from #177 with improvements to image-template formatting validation and base-image configuration documentation.
Linked Issues check	✅ Passed	Check skipped because no linked issues were found for this pull request.
Out of Scope Changes check	✅ Passed	Check skipped because no linked issues were found for this pull request.

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