---
title: "See the canonical form"
description: "Print what a document means (defaults, disjunctions and all) instead of what it resolves to."
source: "https://aontu.dev/how-to/see-canonical-form/"
---

# See the canonical form

Print what a document means (defaults, disjunctions and all) instead of what it resolves to.

Rendered from [`docs/how-to/see-canonical-form.md`](https://github.com/aontu-lang/aontu/blob/main/docs/how-to/see-canonical-form.md) in the engine repository, where a correction belongs, and where the test suite executes every example on this page.

Generation answers “what does this resolve to?”, and in answering it erases the thing a schema author cares about: what the document still admits. The canonical form keeps that. Write `timeout.aon`:

```aontu
timeout: *30|integer
```

Now evaluate it both ways:

```sh
$ aontu timeout.aon
{
  "timeout": 30
}
$ aontu --canon timeout.aon
{"timeout":*30|integer}
```

Generation resolves the default; `--canon` keeps the whole default-and-type so you can see what a caller may still override. Where information has fully arrived, the two agree: a constraint [met](https://aontu.dev/docs/unification) by a concrete value canons to just the value. Write `pinned.aon`:

```aontu
a: 1
a: number
```

```sh
$ aontu --canon pinned.aon
{"a":1}
```

From code, the same view is the `canon` property of a unified value:

```ts
aontu.unify('a: *1 | number').canon   // '{"a":*1|number}'
aontu.unify('a: 1 a: number').canon   // '{"a":1}'
```

```go
v, _ := a.Unify("a: *1 | number")   // v.Canon() == `{"a":*1|number}`
```

A conflict throws before there is anything to read, so ask for the wreckage with `collect: true` ([collect errors](https://aontu.dev/how-to/collect-errors)); the failed path reads `nil`:

```ts
aontu.unify('a: number a: string', { collect: true }).canon  // '{"a":nil}'
```

Canon is deterministic and reparseable, which is why it carries more weight than a debugging view: it is the text the `aon1-` pin is derived from, so “same canon” is this project’s working definition of “same meaning” ([pin a document hash](https://aontu.dev/how-to/pin-a-document-hash)).

The exhaustive rendering rules (key order, number forms, what recursion renders as) are in the language reference under [Canonical form](https://aontu.dev/docs/reference-language#canonical-form).