# `Artefact.Error.Operation`
[🔗](https://github.com/diffo-dev/artefactory/blob/v0.2.0/lib/artefact/error/operation.ex#L4)

Op-specific outcomes that prevent an operation from proceeding even
when its inputs are valid.

Returned as `{:error, %Artefact.Error.Operation{op: op, tag: tag, details: details}}`
from the operation that couldn't proceed. Raised by the `!` variants.

Tags by op:

  * `combine` — `:no_shared_bindings`
  * `harmonise` — `:self_harmonise` (details: `%{uuid: ...}`),
    `:same_base_label` (details: `%{base_label: ...}`)
  * `graft` — `:missing_uuid` (details: `%{key: ...}`),
    `:invalid_uuid` (details: `%{key: ..., uuid: ...}`),
    `:invalid_labels` (details: `%{key: ..., labels: ...}`),
    `:invalid_properties` (details: `%{key: ..., properties: ...}`),
    `:duplicate_keys` (details: `%{keys: [...]}`),
    `:unknown_rel_key` (details: `%{key: ...}`),
    `:islands` (details: `%{keys: [...]}`)

`:details` is always a map; empty when the tag carries no extra info.

# `exception`

```elixir
@spec exception(opts :: Keyword.t()) :: %Artefact.Error.Operation{
  __exception__: true,
  bread_crumbs: term(),
  class: term(),
  details: term(),
  op: term(),
  path: term(),
  splode: term(),
  stacktrace: term(),
  tag: term(),
  vars: term()
}
```

Create an `Elixir.Artefact.Error.Operation` without raising it.

## Keys

- :op
- :tag
- :details

---

*Consult [api-reference.md](api-reference.md) for complete listing*