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08_errors.md

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Errors

Nearly all errors and warnings produced by the yaml parser functions contain the following fields:

Member Type Description
code string An identifier for the error type.
linePos { line: number, col: number } ⎮ undefined If prettyErrors is enabled and offset is known, the one-indexed human-friendly source location.
name 'YAMLParseError' ⎮ 'YAMLWarning'
message string A human-readable description of the error
offset number The offset in the source at which this error or warning was encountered. May be -1 if the offset could not be determined.

A YAMLParseError is an error encountered while parsing a source as YAML. They are included in the doc.errors array. If that array is not empty when constructing a native representation of a document, the first error will be thrown.

A YAMLWarning is not an error, but a spec-mandated warning about unsupported directives or a fallback resolution being used for a node with an unavailable tag. They are included in the doc.warnings array.

In rare cases, the library may produce a more generic error. In particular, TypeError may occur when parsing invalid input using the json schema, and ReferenceError when the maxAliasCount limit is enountered.

To identify errors for special handling, you should primarily use code to differentiate them from each other.

Code Description
ALIAS_PROPS Unlike scalars and collections, alias nodes cannot have an anchor or tag associated with it.
BAD_DIRECTIVE Only the %YAML and %TAG directives are supported, and they need to follow the specified strucutre.
BAD_DQ_ESCAPE Double-quotes strings may include \ escaped content, but that needs to be valid.
BAD_INDENT Indentation is important in YAML, and collection items need to all start at the same level. Block scalars are also picky about their leading content.
BAD_PROP_ORDER Anchors and tags must be placed after the ?, : and - indicators.
BAD_SCALAR_START Plain scalars cannot start with a block scalar indicator, or one of the two reserved characters: @ and `. To fix, use a block or quoted scalar for the value.
BLOCK_AS_IMPLICIT_KEY There's probably something wrong with the indentation, or you're trying to parse something like a: b: c, where it's not clear what's the key and what's the value.
BLOCK_IN_FLOW YAML scalars and collections both have block and flow styles. Flow is allowed within block, but not the other way around.
COMMENT_SPACE Comments need to be separated from their preceding content by a space.
IMPOSSIBLE This really should not happen. If you encounter this error code, please file a bug.
KEY_OVER_1024_CHARS Due to legacy reasons, implicit keys must have their following : indicator after at most 1k characters.
MISSING_ANCHOR Aliases can only dereference anchors that are before them in the document.
MISSING_CHAR Some character or characters are missing here. See the error message for what you need to add.
MULTILINE_IMPLICIT_KEY Implicit keys need to be on a single line. Does the input include a plain scalar with a : followed by whitespace, which is getting parsed as a map key?
MULTIPLE_ANCHORS A node is only allowed to have one anchor.
MULTIPLE_DOCS A YAML stream may include multiple documents. If yours does, you'll need to use parseAllDocuments() to work with it.
MULTIPLE_TAGS A node is only allowed to have one tag.
TAB_AS_INDENT Only spaces are allowed as indentation.
TAG_RESOLVE_FAILED Something went wrong when resolving a node's tag with the current schema.
UNEXPECTED_TOKEN A token was encountered in a place where it wasn't expected.

Silencing Errors and Warnings

Some of the errors encountered during parsing are required by the spec, but are caused by content that may be parsed unambiguously. To ignore these errors, use the strict: false option:

  • COMMENT_SPACE: Comments must be separated from other tokens by white space characters (only when preceding node is known to have ended)
  • MULTILINE_IMPLICIT_KEY: Implicit keys of flow sequence pairs need to be on a single line
  • KEY_OVER_1024_CHARS: The : indicator must be at most 1024 chars after the start of an implicit block mapping key

For additional control, set the logLevel option to 'error' (default: 'warn') to silence all warnings. Setting logLevel: 'silent' will ignore parsing errors completely, resulting in output that may well be rather broken.