fix(enrichment tables): prevent crash on config reload with enrichment table sources

[esensar]

Summary

Diff calculation considered source keys (which are different than component keys in the case of enrichment tables) to find differences in configuration. This caused crashes when that component couldn't be found, because it has a different key in the configuration. This fix changes that to use the original component key for such lookups.

Vector configuration

Any configuration with an enrichment table configured to also act as a source, but I have used an example from one omy previous tests (#23815):

enrichment_tables:
  memory_table:
    type: memory
    ttl: 10
    flush_interval: 5
    inputs: ["cache_generator"]
    source_config:
       source_key: "memory_table_source"
       export_expired_items: true

sources:
  demo_logs_test:
    type: "demo_logs"
    format: "json"

transforms:
  demo_logs_processor:
    type: "remap"
    inputs: ["demo_logs_test"]
    source: |
      . = parse_json!(.message)
      user_id = get!(., path: ["user-identifier"])

      # Look for existing value in the table, using "user-identifier" as key
      existing, err = get_enrichment_table_record("memory_table", { "key": user_id })

      if err == null {
        . = existing.value
        .source = "cache"
      } else {
        .referer = parse_url!(.referer)
        .referer.host = encode_punycode!(.referer.host)
        .source = "transform"
      }

  cache_generator:
    type: "remap"
    inputs: ["demo_logs_processor"]
    source: |
      existing, err = get_enrichment_table_record("memory_table", { "key": get!(., path: ["user-identifier"]) })
      if err != null {
        data = .
        . = set!(value: {}, path: [get!(data, path: ["user-identifier"])], data: data)
      } else {
        . = {}
      }

# We can observe that after some time data will be dumped to console from the cache
sinks:
  console:
    inputs: ["memory_table_source.expired"]
    target: "stdout"
    type: "console"
    encoding:
      codec: "json"

How did you test this PR?

Ran the above configuration and issued kill -HUP {pid} targeting the Vector process. Before this patch, crash occurred:

2025-10-16T13:39:49.363211Z  INFO vector::topology::running: Reloading running topology with new configuration.

thread 'main' panicked at src/config/diff.rs:140:58:
no entry found for key
note: run with `RUST_BACKTRACE=1` environment variable to display a backtrace

After the patch, the crash no longer occurs and reload is successfully executed.

Change Type

• Bug fix
• New feature
• Non-functional (chore, refactoring, docs)
• Performance

Is this a breaking change?

• Yes
• No

Does this PR include user facing changes?

• Yes. Please add a changelog fragment based on our guidelines.
• No. A maintainer will apply the no-changelog label to this PR.

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Sponsored by Quad9

[pront]

Is this something that we can unit test?