# `Schooner.Diagnostic`
[🔗](https://github.com/ausimian/schooner/blob/1.2.0/lib/schooner/diagnostic.ex#L1)

A problem `Schooner.check/3` found in a script without running it.

  * `:severity` — `:error` for a problem that fails the script if
    evaluation reaches it, `:warning` for one that may not.
  * `:code` — what kind of problem it is:
      * `:read_error` — the source doesn't parse.
      * `:syntax_error` — a special form, macro use or `import` set
        is malformed.
      * `:unknown_library` — an `(import ...)` names a library the
        environment doesn't provide.
      * `:unbound` — a name isn't bound by the environment, an
        import, or a definition in the script.
      * `:arity` — a call's argument count can't match the arity of
        the procedure it calls.
  * `:message` — a description for people, without the location.
  * `:location` — the `Schooner.Location` of the problem, naming the
    file passed to `Schooner.check/3` as `:file`, or `nil` when no
    position is known.

# `code`

```elixir
@type code() :: :read_error | :syntax_error | :unknown_library | :unbound | :arity
```

# `severity`

```elixir
@type severity() :: :error | :warning
```

# `t`

```elixir
@type t() :: %Schooner.Diagnostic{
  code: code(),
  location: Schooner.Location.t() | nil,
  message: binary(),
  severity: severity()
}
```

# `format`

```elixir
@spec format(t()) :: binary()
```

Render a diagnostic on one line, as `mix schooner.check` prints it:
`file:line:col: severity[code]: message`.

    iex> Schooner.Diagnostic.format(%Schooner.Diagnostic{
    ...>   severity: :error,
    ...>   code: :unbound,
    ...>   message: "unbound variable: unit-prise",
    ...>   location: %Schooner.Location{file: "draft.scm", line: 1, column: 27}
    ...> })
    "draft.scm:1:27: error[unbound]: unbound variable: unit-prise"

A location without a file renders as `line:col`; a diagnostic
without a location starts at the severity.

---

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