Make Index.mediaType optional to comply with OCI spec #368
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Hi @blark thanks for the contribution! Could you follow a similar pattern to what was done in this PR #347 for Index.mediaType? We're hoping to only use optionals in the spec definitions for pointer types. Other types that are defined omitempty in the oci spec, we will rely on the use of custom JSON decoders to ensure similar behavior to omitempty for non-pointer types in go. |
The mediaType field in the Index struct was defined as a required field, but according to the OCI Image Index Specification, this field is optional: https://github.com/opencontainers/image-spec/blob/main/image-index.md This caused failures when loading OCI archives where the index.json omits the top-level mediaType field, which is valid per the spec. Tools like skopeo can generate such archives. Error before fix: keyNotFound(CodingKeys(stringValue: "mediaType", intValue: nil)) Changes: - Changed Index.mediaType from String to String? - Updated initializer to accept optional mediaType parameter - Added comment documenting that field is optional per OCI spec Fixes: apple/container#330
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Thanks for the feedback @katiewasnothere! I've updated the PR to follow the pattern from #347:
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dcantah
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Oct 29, 2025
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The
mediaTypefield in theIndexstruct was defined as a required field, but according to the OCI Image Index Specification, this field is optional.This caused failures when loading OCI archives where the
index.jsonomits the top-levelmediaTypefield, which is valid per the spec. Tools like skopeo can generate such archives.Error before fix
Changes
Index.mediaTypefromStringtoString?mediaTypeparameterTesting
Verified that OCI archives without a top-level
mediaTypefield inindex.jsonnow load successfully.Fixes apple/container#330