fix: Add useful debug message when files are missing from config

[dmcilvaney]

Merge Checklist

All boxes should be checked before merging the PR (just tick any boxes which don't apply to this PR)

• The toolchain has been rebuilt successfully (or no changes were made to it)
• The toolchain/worker package manifests are up-to-date
• Any updated packages successfully build (or no packages were changed)
• Packages depending on static components modified in this PR (Golang, *-static subpackages, etc.) have had their Release tag incremented.
• Package tests (%check section) have been verified with RUN_CHECK=y for existing SPEC files, or added to new SPEC files
• All package sources are available
• cgmanifest files are up-to-date and sorted (./cgmanifest.json, ./toolkit/scripts/toolchain/cgmanifest.json, .github/workflows/cgmanifest.json)
• LICENSE-MAP files are up-to-date (./LICENSES-AND-NOTICES/SPECS/data/licenses.json, ./LICENSES-AND-NOTICES/SPECS/LICENSES-MAP.md, ./LICENSES-AND-NOTICES/SPECS/LICENSE-EXCEPTIONS.PHOTON)
• All source files have up-to-date hashes in the *.signatures.json files
• sudo make go-tidy-all and sudo make go-test-coverage pass
• Documentation has been updated to match any changes to the build system
• Ready to merge

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Summary

Improve error messages when image config files reference missing files (PackageLists, scripts, AdditionalFiles, etc.).

Previously, if a referenced file was missing, Make would fail with a confusing message about having no rule to build the validation flag. If the missing file was in a non-existent directory, realpath would also print unhelpful errors before the actual failure.

This was caused by Make's pattern rule matching behavior. The validation rules is $(STATUS_FLAGS_DIR)/validate-image-config%.flag:, which matches the variable validate-config = $(STATUS_FLAGS_DIR)/validate-image-config-$(config_name).flag

The rule had config_other_files = $(if $(CONFIG_FILE),$(call shell_real_build_only, $(SCRIPTS_DIR)/get_config_deps.sh $(CONFIG_FILE)),) as a dependency. If one of those calculated files was missing, then make would consider the pattern matched rule un-usable, and would try to find an alternate rule that did have all its dependencies. Unfortunately, we only have one pattern match rule, so we must ensure that all the dependencies we list are either real files, or valid make targets, so make won't skip it.

Change Log

• Add early validation in imggen.mk to detect missing config dependencies and display a clear error message listing all missing files
• Use realpath -m in get_config_deps.sh to handle paths where parent directories don't exist
• Skip the missing file check for printvar-* targets so users can still debug

Does this affect the toolchain?

NO

Test Methodology

• Local testing with intentionally broken config files referencing missing files in both existing and non-existing directories
• pipeline: https://dev.azure.com/mariner-org/mariner/_build/results?buildId=1025897&view=results
• pipeline: https://dev.azure.com/mariner-org/mariner/_build/results?buildId=1028007&view=results

[anphel31]

does this intentionally include 2 newlines?

[dmcilvaney]

Yes, make trims the last one off, so to get one newline, you need two.

[Copilot]

Pull request overview

This PR improves error handling when image configuration files reference missing dependencies. Previously, Make would fail with a confusing "no rule to make target" error. Now, users get a clear, actionable error message listing all missing files.

Changes:

• Add a newline helper in utils.mk for formatting multi-line error messages
• Implement early validation in imggen.mk to detect missing config dependencies before Make processes them
• Modify get_config_deps.sh to use realpath -m so it can handle paths in non-existent directories

Reviewed changes

Copilot reviewed 3 out of 3 changed files in this pull request and generated 1 comment.

File	Description
toolkit/scripts/utils.mk	Adds newline variable definition for formatting error messages
toolkit/scripts/imggen.mk	Adds validation logic to check for missing config files and display helpful error messages
toolkit/scripts/get_config_deps.sh	Uses realpath -m flag to canonicalize paths even when parent directories don't exist

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[Copilot]

Grammar error: 'its' should be "it's" (it is). The contraction is needed here since you're saying "it is a pattern match".

Suggested change

	# the validation flag (since its a pattern match and if a dependency is missing, it can't match the pattern)
	# the validation flag (since it's a pattern match and if a dependency is missing, it can't match the pattern)

[christopherco]