Formating output of `oras manifest fetch` with go-templates doesn't work on all fields

[ggjulio]

What happened in your environment?

I'm trying to get the value of some fields in a manifest.

manifest example

{
  "schemaVersion": 2,
  "mediaType": "application/vnd.oci.image.manifest.v1+json",
  "config": {
    "mediaType": "application/vnd.cncf.helm.config.v1+json",
    "digest": "sha256:eaea14941b04bcdb0595c359a31f8dab61f137299c9fa5410c74d2408cda1789",
    "size": 220
  },
  "layers": [
    {
      "mediaType": "application/vnd.cncf.helm.chart.content.v1.tar+gzip",
      "digest": "sha256:0090c532386f29b8436c34eb56055e922f2d0fd6adda1b83fc924717b1ae994f",
      "size": 45915,
      "annotations": {
        "org.opencontainers.image.title": "target/dh-7.5.0-0-SNAPSHOT.tgz"
      }
    }
  ],
  "annotations": {
    "org.opencontainers.image.authors": "redacted,
    "org.opencontainers.image.created": "2025-12-17T09:20:56Z",
    "org.opencontainers.image.description": "redacted",
    "org.opencontainers.image.revision": "e12fb7954a7e8cbfa61b4fd740fd70519f137cbb",
    "org.opencontainers.image.title": "redacted",
    "org.opencontainers.image.vendor": "redacted",
    "org.opencontainers.image.version": "0.1.0"
  }
}

This one works:

• oras manifest fetch --format go-template --template='{{ index .mediaType }}' $OCI_REF

Theses one don't

• oras manifest fetch --format go-template --template='{{ .config.mediaType }}' $OCI_REF
• oras manifest fetch --format go-template --template='{{ index .config.mediaType }}' $OCI_REF
• oras manifest fetch --format go-template --template='{{ index .annotations "org.opencontainers.image.revision"}}' $OCI_REF

Log output example:

$> oras manifest fetch --format go-template --template='{{ index .annotations }}' $OCI_REF
Error: template: format output:1:3: executing "format output" at <index .annotations>: error calling index: index of untyped ni

Maybe related to this: #1276

What did you expect to happen?

No response

How can we reproduce it?

.

What is the version of your ORAS CLI?

Version: 1.3.0
Go version: go1.25.0
OS/Arch: linux/amd64
Git commit: 40530fe
Git tree state: clean

What is your OS environment?

debian trixie

Are you willing to submit PRs to fix it?

• Yes, I am willing to fix it.

[github-actions]

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