Artifact Contract

DocShell writes JSON artifacts for renderers that may live in other repositories and release on their own cadence. Those JSON shapes are public API, not an internal data structure. This notebook walks through the contract using a real build so each field is tied to something you can inspect.

The examples write to a disposable temp directory. They do not modify priv/doc_shell/.

What is public API

The contract includes:

the artifact tree
the envelope around every JSON payload
the doc-shell/v1 schema version
the shape of navigation.json, search-index.json, content.json, modules.json, guides.json, livebooks.json, changelog.json, openapi.json, and manifest.json
the in-memory presentation shape accepted from graph-backed hosts

Changing one of those shapes is a breaking change unless it is strictly backward-compatible.

Setup

Run this notebook from Livebook's default standalone runtime. The setup cell installs the matching DocShell release from Hex. Release tooling updates this version together with the package and the notebook links.

Mix.install([
  {:doc_shell, "== 0.3.0"}
])

Application.ensure_all_started(:doc_shell)
DocShell.schema_version()

Build a small artifact tree

The fixture has one module, one Markdown guide, one Livebook notebook, and the default empty OpenAPI document.

workspace =
  Path.join(
    System.tmp_dir!(),
    "doc_shell_artifact_contract_#{System.unique_integer([:positive])}"
  )

File.rm_rf!(workspace)

guide_dir = Path.join(workspace, "guides")
livebook_dir = Path.join(workspace, "notebooks")
public_dir = Path.join(workspace, "public")
private_dir = Path.join(workspace, "private")

Enum.each([guide_dir, livebook_dir, public_dir, private_dir], &File.mkdir_p!/1)

File.write!(Path.join(guide_dir, "contract-guide.md"), """
---
id: contract-guide
title: Contract Guide
audience: developers
locale: en
---

# Contract Guide

The renderer reads this guide through `content.json`.
""")

File.write!(Path.join(livebook_dir, "operator-runbook.livemd"), """
# Operator Runbook

Operational notebooks are indexed as documentation, but DocShell does not run
their code.

```elixir
:ok
```
""")

build_opts = [
  modules: [DocShell.Config],
  guide_bases: [guide_dir],
  livebook_base: livebook_dir,
  public_dir: public_dir,
  private_dir: private_dir
]

{:ok, result} = DocShell.Build.run(build_opts)

%{
  public_dir: public_dir,
  private_dir: private_dir,
  presentation_keys: Map.keys(result.presentation) |> Enum.sort()
}

The artifact tree

DocShell writes public renderer artifacts under :public_dir and a separate manifest under :private_dir.

Path.wildcard(Path.join(workspace, "**/*.json"))
|> Enum.map(&Path.relative_to(&1, workspace))
|> Enum.sort()

The three files most renderers read directly are:

navigation.json
search-index.json
content.json

The source indexes and openapi.json are still public artifacts. They are useful for ingestion, search, coverage reporting, and API reference tooling.

The envelope

Every artifact file has the same outer object. DocShell.Artifact.read/1 returns only "data"; use read_envelope/1 when the envelope itself matters.

{:ok, navigation_envelope} =
  DocShell.Artifact.read_envelope(Path.join(public_dir, "navigation.json"))

Map.take(navigation_envelope, ["schema_version", "generated_at", "generation_id"])

The fields are:

Field	Meaning
`schema_version`	The public contract version, currently `doc-shell/v1`
`generated_at`	ISO 8601 UTC timestamp for the build
`generation_id`	Opaque id shared by every artifact in one build
`data`	The payload for that artifact

generation_id is only for equality checks. Do not sort by it, decode meaning from it, or reuse it between builds.

One generation per tree

Every public artifact and the public manifest from one build share a generation id. The runtime cache uses that to reject mixed snapshots.

Path.wildcard(Path.join(public_dir, "*.json"))
|> Map.new(fn path ->
  {:ok, envelope} = DocShell.Artifact.read_envelope(path)
  {Path.basename(path), envelope["generation_id"]}
end)

The value should be the same for every file in that map.

manifest.json

The manifest describes exactly the artifacts beside it. It is written last and acts as the commit marker for a generation.

{:ok, public_manifest} = DocShell.Artifact.read(Path.join(public_dir, "manifest.json"))

public_manifest["artifacts"] |> Enum.sort()

The private directory has its own manifest. Today the default build writes no private artifacts, so the list is empty.

DocShell.Artifact.read(Path.join(private_dir, "manifest.json"))

Each manifest describes its own directory. A shared manifest would lie about at least one side of a public/private split.

navigation.json

navigation.json is a list of navigation items. On disk, structs have encoded to maps with string keys.

{:ok, navigation} = DocShell.Artifact.read(Path.join(public_dir, "navigation.json"))

navigation
|> Enum.map(&Map.take(&1, ["id", "title", "path", "kind", "children", "meta"]))

The default DocShell.Presentation.StaticGenerator sorts entries by kind then title and leaves children empty. Hierarchy belongs to the host: maybe modules group by namespace, guides group by product area, and notebooks group by team. DocShell cannot guess that correctly.

search-index.json

search-index.json has document identity, route path, flattened text, optional tokens, and scoping fields.

{:ok, search} = DocShell.Artifact.read(Path.join(public_dir, "search-index.json"))

search
|> Enum.find(&(&1["id"] == "contract-guide"))
|> Map.take(["id", "title", "path", "kind", "audience", "locale", "content", "tokens"])

audience and locale are present as null when unset. For guides, they come from frontmatter. For modules and Livebooks they are usually null.

Tokens are present but empty by default because they duplicate data already in content. Enable them only when a host search backend wants a pre-split field.

{:ok, token_result} = DocShell.Build.run(Keyword.put(build_opts, :search_tokens, true))

token_result.presentation.search
|> Enum.find(&(&1.id == "contract-guide"))
|> Map.take([:id, :tokens])

content.json

content.json maps each entry id to its parsed Markdown AST. This is where page bodies live.

{:ok, content} = DocShell.Artifact.read(Path.join(public_dir, "content.json"))

Map.keys(content) |> Enum.sort()

A content node is recursive. Text nodes are plain strings. Element nodes always carry the same four keys: tag, attrs, content, and meta.

content["contract-guide"] |> List.first()

That uniform shape is why a renderer can use one walker for module docs, guides, and notebooks.

modules.json, guides.json, livebooks.json, and changelog.json

The per-source indexes carry identity and metadata for every extracted entry. They intentionally do not carry "ast"; the body already lives once in content.json.

{:ok, module_index} = DocShell.Artifact.read(Path.join(public_dir, "modules.json"))
{:ok, guide_index} = DocShell.Artifact.read(Path.join(public_dir, "guides.json"))
{:ok, livebook_index} = DocShell.Artifact.read(Path.join(public_dir, "livebooks.json"))
{:ok, changelog_index} = DocShell.Artifact.read(Path.join(public_dir, "changelog.json"))

%{
  modules: Enum.map(module_index, &Map.take(&1, ["id", "title", "kind", "meta"])),
  guides: Enum.map(guide_index, &Map.take(&1, ["id", "title", "kind", "meta"])),
  livebooks: Enum.map(livebook_index, &Map.take(&1, ["id", "title", "kind", "meta"])),
  changelog: Enum.map(changelog_index, &Map.take(&1, ["id", "title", "kind", "meta"]))
}

The source indexes are unfiltered. If skip_empty removes an undocumented module from presentation, the module still appears in modules.json, which makes the file useful as a coverage report.

The doc-shell/v1 source catalogue is additive. Producers may add a new per-source index to manifest.json, and entry kind values are open strings. Generic renderers ignore unknown source files and kinds; selective consumers may continue reading only their supported artifacts. Removing a known artifact or removing, renaming, or retyping a known field requires a schema-version change.

module_index
|> List.first()
|> Map.has_key?("ast")

openapi.json

openapi.json contains the OpenAPI document returned by the configured adapter. With no adapter, DocShell writes a valid empty OpenAPI 3.1 document.

{:ok, openapi} = DocShell.Artifact.read(Path.join(public_dir, "openapi.json"))

Map.take(openapi, ["openapi", "info", "paths"])

Because the artifact is enveloped, standard OpenAPI tooling should not be pointed at priv/doc_shell/public/openapi.json. Set :openapi_spec_path when a tool needs the bare OpenAPI document.

In-memory presentation vs. disk JSON

Before encoding, presentation data uses structs and atom keys.

result.presentation.navigation |> List.first()

After reading from disk, the same artifact is JSON data with string keys.

navigation |> List.first()

Both are intentional. Application code gets typed structs while artifacts stay plain JSON.

Graph-backed presentation

Graph-backed hosts can provide their own presentation data through DocShell.Presentation.GraphProjector. The required shape is the same concept: schema version, navigation, search, and content. backlinks are optional.

presentation = %{
  schema_version: DocShell.schema_version(),
  navigation: [],
  search: [],
  content: %{},
  backlinks: %{
    "contract-guide" => [
      %DocShell.Presentation.Backlink{
        id: "operator-runbook",
        title: "Operator Runbook",
        path: "/docs/livebook/operator-runbook"
      }
    ]
  }
}

DocShell.Presentation.GraphProjector.validate(presentation)

The validator exists because a projector may live in another repository. A shape mistake should fail at the boundary, not later as a renderer bug.

Contract change checklist

Before changing any doc-shell/v1 shape, answer these questions:

Question	Why it matters
Does a renderer already read this field?	Removing or retyping it is breaking
Can the change be additive and optional?	Optional additions are usually safe
Does the value stay JSON-native?	Artifacts must not leak Elixir-only terms
Does the schema version need to change?	Breaking changes require coordination
Are README, usage rules, and tutorials updated?	The contract docs are part of the API

The safest rule is conservative: if a renderer could observe the change, treat it as public API work.

Rendering untrusted content

The AST preserves raw HTML and URL schemes. Renderers must allow-list tags and attributes, reject unsafe URL schemes, and escape text for their output context. Parsing Markdown is not sanitization.

Recursive content validation

Host projectors and changelog sources must provide complete recursive AST nodes and JSON metadata with string keys. Invalid nested content fails validation before output is written. DocShell.Ast.valid?/1 checks node lists.

Concurrent artifact writers

Individual artifact writes use exclusively created random temporary files in the destination directory, so independent BEAM instances cannot share a temporary file. A rename publishes each complete file.

Search text

Search content preserves adjacent inline text, including words split by formatting. Block elements and line breaks add separators; image alt text is searchable. Token generation uses this same text.

Document paths

Each document path is calculated once and reused by navigation and search. Default paths percent-encode kind and ID as individual URL segments. Use a custom path_builder when IDs intentionally represent a path hierarchy.

Legacy envelope compatibility

Artifact.read/1 and read_envelope/1 accept legacy v1 envelopes without generation_id. A present ID must be a nonempty string. Runtime caches require an ID on every artifact and manifest to verify that they form one generation.

Presentation structs and backlinks

Presentation structs serialize through Jason.Encoder into the documented string-keyed objects. DocShell.Json.stringify/1 instead converts arbitrary structs into text and must not be used to serialize presentation structs. Projector backlinks are validated and available in the in-memory build result; the build does not write a backlinks artifact.

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