StringYamlParser class final

A production-ready, streaming YAML 1.2 parser that converts a YAML string into a normalized stream of YamlTokens.

StringYamlParser is the core pull-based YAML parser used by JetLeaf. It implements the full YAML 1.2 grammar including:

  • Mappings (flow and block)
  • Sequences (flow and block)
  • Anchors (&foo) and aliases (*foo)
  • Tags (!!str, !<verbatim:tag>, custom tags)
  • Block scalars (| literal and > folded)
  • Chomping indicators (|+ / |-)
  • Indentation-sensitive parsing
  • Multi-document streams (--- / ...)

The parser is designed for:

  • High performance (single-pass tokenizer)
  • Low memory usage (pull API, no tree construction)
  • Spec correctness (YAML 1.2 compliant)
  • Robust error handling (precise line/column diagnostics)

Usage Example

final parser = StringYamlParser(source);

while (parser.nextToken()) {
  final token = parser.getCurrentToken();
  final value = parser.getCurrentValue();
  print('$token  $value');
}

await parser.close();

Key Features

  • Emits one YamlToken at a time (pull model)
  • Can skip entire nested collections via skip
  • Maintains anchor resolution tables
  • Handles all scalar styles (plain, quoted, literal, folded)
  • Properly manages indentation and flow contexts
  • Produces detailed YamlException errors with source positions

Token Stream Example

YAML:

person:
  name: Alice
  age: 30

Produces:

MAPPING_START
KEY     -> "person"
MAPPING_START
KEY     -> "name"
SCALAR  -> "Alice"
KEY     -> "age"
SCALAR  -> "30"
MAPPING_END
MAPPING_END
END_DOCUMENT

Lifecycle

  • Create parser with input string
  • Call nextToken until it returns false
  • Inspect tokens + values
  • Call close to release buffers

Error Handling

Any structural error throws a YamlException that includes:

  • Error message
  • Line/column position
  • Stack trace for debugging

The implementation closely follows the YAML 1.2 specification and is optimized for correctness over convenience. Higher-level JetLeaf layers (deserializers, builders, AST models) consume this parser.

See also:

  • YamlScanner — low-level character scanner
  • YamlToken — token enumeration
  • BlockScalarChomping — block scalar semantics
  • YamlStyle — scalar style indicators
Implemented types

Constructors

StringYamlParser(String input)
Creates a new YAML parser for the given input String.

Properties

hashCode → int
The hash code for this object.
no setterinherited
runtimeType → Type
A representation of the runtime type of the object.
no setterinherited

Methods

close() → FutureOr<void>
Closes this resource, relinquishing any underlying resources.
getAlias() → String?
Returns the alias reference if this token is an alias.
override
getAnchor() → String?
Returns the anchor name if this token is anchored.
override
getCurrentToken() → YamlToken?
Returns the current token after a successful nextToken call.
override
getCurrentValue() → String?
Returns the text or raw value associated with the current token.
override
nextToken() → bool
Advances the parser to the next token.
override
noSuchMethod(Invocation invocation) → dynamic
Invoked when a nonexistent method or property is accessed.
inherited
skip() → void
Skips the entire nested structure at the current cursor position.
override
toString() → String
A string representation of this object.
inherited

Operators

operator ==(Object other) → bool
The equality operator.
inherited