fastrag.ingestion.steps.parsing.base#

The Parser family base.

docs/specification/subclasses.md: Parser is the DocumentStep every concrete parser (HtmlParser, DefaultParser, ParserRouter) extends. Parsers convert supplied content and may call content-selection or vision models within the async transform contract. Fetchers own page downloads, JavaScript rendering, and browser interaction.

Classes

Parser(*[, cache, policy])

Turns raw Source bytes into text.

class fastrag.ingestion.steps.parsing.base.Parser(*, cache=None, policy=None)[source]#

Bases: DocumentStep, ABC

Turns raw Source bytes into text.

One source may yield several documents, which is why transform() (inherited abstract from DocumentStep) returns an async iterator rather than a single document. Binding an upstream (parser(sources), via the inherited __call__) and evaluating it (async for document in parser / run()) never runs a parse eagerly — only consuming the resulting stream does.

Every event a parser emits is labelled "Parsing", inherited by every concrete parser (HtmlParser, DocusaurusParser, ParserRouter, …) unless it declares an event_name of its own.

Parameters:

cache (CacheStore | Literal[False] | None)
policy (Policy | None)

event_name: str = 'Parsing'#

The stage this step’s work belongs to, e.g. "Chunking".

Declared as a plain class attribute by a family base class, and inherited by every concrete step in that family:

class Chunker(DocumentStep, ABC):
    event_name = "Chunking"


class ChunkerRouter(RoutedStep[Document], Chunker):
    ...  # -> "Chunking", inherited from `Chunker`

A concrete step overrides it to opt out of its family’s label:

class ChunkerRouter(RoutedStep[Document], Chunker):
    event_name = "ChunkerRouter"  # -> "ChunkerRouter"

Resolution walks the MRO for the first class that declares it in its own class body (so a mixin listed first, e.g. RoutedStep, contributes nothing unless it declares one itself), and falls back to the class’s own name when nothing in the MRO does — a step family that never declares an event_name still labels each of its steps distinctly rather than collapsing them under one blank heading. That fallback is computed per instance rather than assigned onto the class: assigning it would make it look “declared” to every subclass, which would then inherit their base’s name instead of getting their own.

content_format: ContentFormat = 'text'#: The ContentFormat this parser’s documents carry by default, stamped by build_document() into metadata["content_format"]. Override on a subclass whose output is always one format (HtmlParser/DocusaurusParser set MARKDOWN); pass content_format= to a single build_document() call instead for a parser whose output format depends on its own configuration.

accepted_media_types: frozenset[str] | None = None#: None retains legacy permissiveness; MIME patterns may use type/*.

property config_hash: str#: Invalidate cached documents created before source-aware identities.

validate_input(item)[source]#

Validate declared source capabilities before work and cache replay.

Parameters:: item (Source)
Return type:: None

async evaluate(context)[source]#

Emit DocumentParsed per document.

Wraps DocumentStep’s concrete evaluate (which already resolved, per item, whether the document came from cache or a fresh transform() call — document.cached is trustworthy either way) rather than emitting inside a concrete parser’s own transform(), so the event fires the same way for a cache hit as for a fresh parse, and exactly once regardless of how many layers of routing (e.g. ParserRouter) produced the document.

Parameters:: context (ExecutionContext)
Return type:: AsyncIterator[Document]

build_document(source, content, metadata=None, *, content_format=None)[source]#

Build one document from source’s parsed content.

Sets id (a hash of the source identity and parsed content), source_id, step_config_hash (this parser’s own config_hash), and the reserved metadata keys every parser gets right without writing them itself: source_uri, content_type (source’s own, as declared or guessed upstream), and content_format (what kind of string content is — content_format unless overridden for this one call). The site_name/favicon_url a fetcher found on source are carried over too, unless metadata sets its own.

Parameters:

source (Source) – The source content was parsed from.
content (str) – The parsed text.
metadata (dict[str, Any] | None) – Extra metadata to carry, e.g. an HTML page’s title.
content_format (ContentFormat | None) – Overrides content_format for this one document, for a parser whose output format depends on its own configuration rather than being fixed per class.

Return type:

Document

property cache: CacheStore | Literal[False] | None#: Return the cache explicitly configured for this step.

abstractmethod config()#

Return this step’s own configuration, for cache-identity hashing.

Every concrete step declares this explicitly — steps are plain classes, not dataclasses, so there is no automatic field introspection. A step that forgets it cannot be instantiated: config is abstract, so construction itself fails loudly rather than config_hash silently collapsing to a constant.

Return type:: Mapping[str, Any]

effective_policy(context)#

Resolve this step’s policy over the one inherited from context.

The step’s own explicitly-set fields take priority; everything else falls through to the pipeline (or enclosing router/aggregator) policy.

Parameters:: context (ExecutionContext)
Return type:: Policy

async evaluate_items(items, context)#

Transform a bounded cache window independently of worker concurrency.

Parameters:

items (AsyncIterator[Any])
context (ExecutionContext)

Return type:

AsyncIterator[Document]

property policy: Policy | None#: Return the policy explicitly configured for this step.

replay_needs_content: bool = False#: Set by a step whose cached replay reads the full documents anyway (e.g. to re-validate them): its cache reads then skip the header-only projection rather than fetching every entry twice.

async run()#

Execute this step independently and collect every item.

Builds a default ExecutionContext when none is installed (this step’s own policy, or a fresh Policy). Intended primarily for testing and standalone use — pipeline-wide event observation is Pipeline’s job.

Return type:: list[T]

abstractmethod transform(item, context)#

Transform one upstream item into zero or more output documents.

Parameters:

item (Any) – One item from this step’s upstream (a Source for a parser, or a Document for a chunker/embedder).
context (ExecutionContext) – Execution-scoped state and services.

Yields:

The documents this one upstream item produces.

Return type:

AsyncIterator[Document]

property upstream: PipelineStep[Any] | None#

Return the upstream step bound via __call__, or None.

Read-only counterpart to __call__’s self._upstream assignment — lets external code (e.g. Pipeline, walking a graph from its root to classify each step by position) introspect composition without reaching into a private attribute.

name: str#