js-yaml

Changed

• Updated argparse to v3.

• Updated development dependencies.

Fixed

• Correct percent-encoding of shorthand and verbatim tags.

• Reject ,, ], and } at the start of block plain scalars, #801.

• Report the exact position of non-printable characters in errors, #801.

Added

• Added the scalarStyleRules dumper option to customize string formatting. See Scalar styling for details.

Changed

• breaking

  Flattened the low-level AST node style representation. Scalar and collection nodes now use SCALAR_STYLE and COLLECTION_STYLE values; explicit tags use the separate tagged property. Alias nodes now contain only kind and anchor. This only affects code that directly constructs or edits AST nodes.

• breaking

  The sortKeys option was rewritten using AST mutation to avoid side effects.

• Reworked scalar style selection. This can change formatting without changing loaded values; in particular, whitespace-only strings are now double-quoted.

Fixed

• Accept a byte order mark at the start of each document in a stream, #791.

• Produce valid flow mappings with quoteFlowKeys and flowSkipColonSpace, including alias and property-only keys, #786.

• Preserve empty scalar items when converting block sequences to flow style.

• Do not apply the 1024-character simple-key limit to flow mapping keys.

• Count Unicode code points, rather than UTF-16 code units, for the 1024-character simple-key limit.

• Add an explicit document-end marker after keep-chomped block scalars when needed to preserve trailing newlines.

This release focuses on reworking the documentation and making small architectural improvements before moving forward.

Added

• Added completely new documentation.

• Exported DUMP_SCHEMA, the default schema used by the dumper.

• Added YAMLException.throwAt() for throwing an error at a source position.

Changed

• Changed flat constant exports to grouped exports: EVENT_ID, SCALAR_STYLE, COLLECTION_STYLE, and CHOMPING_MODE, along with their value types. The old exports are still preserved, but deprecated.

• Made identify mandatory for custom tag definitions. Use identify: () => false for load-only tags.

Deprecated

• deprecated

  Deprecated flat constant exports. Use grouped ones instead.

Removed

• breaking

  Removed the MERGE_KEY export (not used anymore after last fixes).

Fixed

• Validate << sequence items at merge time, so aliased merge sources are checked too.

• Resolve << outside of a mapping key as the plain string '<<', matching v4, instead of leaking an internal symbol into the result.

Fixed

• Prevent prototype fallback when resolving tags and mapping entries, #782.

• Resolve !!timestamp years 0000-0099 correctly, #775.

• Preserve implicit null mapping values before document markers and reject unpaired mapping event streams, #784.

• Preserve folded scalar values with tab-indented lines when round-tripping a parsed AST through present(); dump() and loading are unaffected, #780.

Added

• Added maxTotalMergeKeys (10000) loader option to limit the total number of keys processed by YAML merge (<<) across one load() / loadAll() call.

• Added maxAliases (-1) loader option to limit the number of YAML aliases per document.

Removed

• breaking

  maxMergeSeqLength replaced with maxTotalMergeKeys for limiting YAML merge processing.

Fixed

• Round-trip of integers with exponential form (>= 1e21)

Added

• Added named exports for schemas, tags, parser events and AST utilities.

• Reworked JSON_SCHEMA and CORE_SCHEMA with spec-compliant scalar resolution rules, and added YAML11_SCHEMA.

• Added realMapTag for lossless mappings with non-string and complex keys. Object-based mappings now reject complex keys instead of stringifying them.

• Added dump() transform option for changing the generated AST before rendering.

• Added dump() options seqInlineFirst, flowBracketPadding, flowSkipCommaSpace, flowSkipColonSpace, quoteFlowKeys, quoteStyle and tagBeforeAnchor.

• Added formal data layers (events and AST) for modular data pipelines.

  • Added low-level parser (to events), presenter and visitor APIs.

• Added the YAML Test Suite to the test set.

Changed

• Rewritten in TypeScript and reorganized the public API around flat named exports.

• Reduced the set of exported schemas:

  • YAML 1.2 schemas: CORE_SCHEMA (loader default), JSON_SCHEMA, FAILSAFE_SCHEMA.

  • YAML11_SCHEMA, a combination of all YAML 1.1 tags (YAML 1.1 does not specify a schema, only "types").

• load/dump default behaviour is now specified exactly via schemas:

  • load uses CORE_SCHEMA, without !!merge by default.

  • dump uses YAML11_SCHEMA + CORE_SCHEMA for the quoting check, to guarantee backward compatibility by default.

• !!set is now loaded as a JavaScript Set.

• Replaced the Type API with a tags API. Similar, but more precise and simpler. See examples for details. Tags can be defined via defineScalarTag(), defineSequenceTag() and defineMappingTag(), or as a spread + override of an existing tag.

• Renamed Schema.extend() to Schema.withTags().

• Expanded YAML 1.2 conformance and improved handling of directives, document markers, block keys, multiline scalars, tag syntax and other things.

• load() now throws on empty input instead of returning undefined.

• Moved browser builds to the js-yaml/browser export.

• deprecated

  Deprecated the loadAll signature with an iterator (still works, but is a candidate for removal).

Removed

• breaking

  Removed deprecated safeLoad(), safeLoadAll() and safeDump() exports.

• breaking

  Removed DEFAULT_SCHEMA and the nested types export.

• breaking

  Removed loader options onWarning, legacy and listener.

• breaking

  Removed dumper options styles, replacer, noCompatMode, condenseFlow, quotingType and forceQuotes. Renamed noArrayIndent to seqNoIndent. Formatting and representation are now configured through presenter options, schemas and tag definitions. See migration guide on how to replace.

• breaking

  Removed support for importing internal files from lib/.