Reference

Issue codes

Match on the code, never on the message: the wording is not part of the API, the code is. Every code is also a static on IssueCode in camelCase — too_small is IssueCode.tooSmall.

Parameters named in a meaning are in issue.params, ready to interpolate into your own wording.

Decoding

Code	Meaning
`invalid_escape`	A string escape that is not one: a lone surrogate, a non-hex `\u` digit. `location` is the backslash. “contains an invalid escape sequence”.
`assayer_conversion_failed`	The value was accepted by the schema but refused by its conversion.
`fallback_applied`	Fell back to the declared value.
`alias_matched`	Was read from its alias “…”. A warning: the field decoded from a `@Key(_:or:)` alias rather than its primary key. Params: `alias`.
`invalid_regex_pattern`	The rule’s pattern … is not a valid regular expression. Params: `pattern`.
`regex_unavailable`	Regular expressions are not available on this platform version.
`unknown_variant`	Params: `options`.

Validation rules

Code	Meaning
`empty`	Must not be empty.
`invalid_email`	Must be a valid email address.
`invalid_hostname`	Must be a valid hostname.
`invalid_url`	Must be a valid URL.
`invalid_uuid`	Must be a valid UUID.
`missing_prefix`	Must start with “…”. Params: `prefix`.
`missing_substring`	Must contain “…”. Params: `substring`.
`missing_suffix`	Must end with “…”. Params: `suffix`.
`negative`	Must not be negative.
`not_ascii`	Must contain only ASCII characters.
`not_finite`	Must be a finite number.
`not_in_range`	Must be between … and …. Params: `maximum`, `minimum`.
`not_lowercased`	Must be lowercase.
`not_multiple`	Must be a multiple of …. Params: `multipleOf`.
`not_negative`	Must be negative.
`not_one_of`	Must be one of …. Params: `options`.
`not_positive`	Must be positive.
`not_trimmed`	Must not have leading or trailing whitespace.
`not_unique`	Must not contain duplicates.
`pattern_mismatch`	Must match the pattern …. Params: `pattern`.
`too_large`	Must be at most …. Params: `maximum`.
`too_small`	Must be at least …. Params: `minimum`.
`wrong_count`	Must contain between … and … items. Params: `maximum`, `minimum`.
`wrong_length`	Must be exactly … character… ? . Params: `length`.

Dates

Code	Meaning
`date_format_fallback`	Matched the fallback format …, . Params: `matched`, `primary`.
`date_not_after`	Must be after …. Params: `bound`.
`date_not_before`	Must be before …. Params: `bound`.
`date_not_between`	Must be between … and …. Params: `maximum`, `minimum`.
`invalid_date`	Params: `expected`, `reason`.
`invalid_rule_date`	The rule’s date bound “…” is not a valid ISO-8601 date. Params: `bound`.

Unions

Code	Meaning
`union_budget_exhausted`	Union backtracking exceeded … attempts (Limits.maxUnionAttempts). Params: `maxUnionAttempts`.
`union_no_variant_matched`	Params: `closest`, `type`, `variants`.
`union_unknown_variant`	Params: `didYouMean`, `known`.

Encoding

Code	Meaning
`extras_key_collision`	Extras key “…” collides with a declared field. Params: `key`.
`unknown_not_encodable`	Params: `type`.
`unrepresentable_value`	Cannot be represented in … (…). Params: `format`.

Content negotiation

Code	Meaning
`missing_content_type`	Content-Type …. Params: `reason`.
`unreadable_charset`	Params: `charset`, `reason`.
`unsupported_media_type`	Media type … is not in the accepted list.

Mapped files (AssayFoundation)

Code	Meaning
`cannot_map_file`	Could not open or map the file.

Property lists (AssayPlist)

Code	Meaning
`plist_amplification`	Property list: …. Params: `reason`.
`plist_bad_date`	—
`plist_bad_magic`	—
`plist_bad_marker`	—
`plist_bad_offset`	—
`plist_bad_real`	—
`plist_bad_reference`	—
`plist_bad_root`	—
`plist_bad_string`	—
`plist_bad_trailer`	—
`plist_bad_value`	—
`plist_cycle`	Property list: …. Params: `reason`.
`plist_int_out_of_range`	—
`plist_int_too_wide`	—
`plist_too_deep`	Property list nests deeper than … levels (Limits.maxDepth). Params: `maxDepth`.
`plist_truncated`	—
`plist_unpaired_key`	—
`plist_unrepresentable_key`	—

TOML (AssayTOML)

Code	Meaning
`toml_bad_date_time`	Invalid date-time.
`toml_bad_escape`	Invalid escape sequence.
`toml_bad_number`	Invalid number literal.
`toml_control_character`	Control characters must be escaped.
`toml_expected_equals`	Expected ‘=’ after the key.
`toml_expected_key`	Expected a key.
`toml_expected_newline`	Expected a newline after the value.
`toml_expected_value`	Expected a value.
`toml_inline_table_closed`	Inline table ‘…’ cannot be extended after it is defined. Params: `key`.
`toml_no_null`	TOML has no null; the value cannot be encoded. Encoding only.
`toml_not_a_table`	‘…’ is not a table and cannot be extended. Params: `key`.
`toml_redefined_table`	Table ‘…’ is already defined. Params: `key`.
`toml_root_not_a_table`	A TOML document is a table; the root value is not. Encoding only.
`toml_unterminated_array`	Unterminated array; expected ‘,’ or ‘]’.
`custom`	`toml_unterminated_inline_table` — “unterminated inline table; expected ‘,’ or ‘}’”.
`toml_unterminated_string`	Unterminated string.
`custom`	`toml_unterminated_table_header` — “expected ‘]’ closing the table header”.

YAML (AssayYAML)

Code	Meaning
`yaml_anchor_on_alias`	An anchor cannot be placed on an alias (`&a *b`); an alias refers to an anchored node and is not a node of its own.
`yaml_bad_escape`	Invalid escape sequence.
`yaml_empty_stream`	The stream contains no documents.
`yaml_expansion_limit`	Alias expansion limit exceeded.
`yaml_expected_colon`	Expected ‘:’ after mapping key.
`yaml_expected_value_indicator`	Expected ‘:’ introducing the value.
`yaml_multiple_documents`	The stream contains multiple documents; use parseAll.
`yaml_undefined_alias`	Alias refers to an undefined anchor.
`yaml_unexpected_in_flow`	Unexpected character in a flow collection; expected ‘,’ or a closing bracket.
`yaml_unrepresentable_key`	A mapping key is not a plain scalar; parse to YAML.Node instead.
`custom`	`yaml_unterminated_flow_mapping` — “unterminated flow mapping”.
`custom`	`yaml_unterminated_flow_sequence` — “unterminated flow sequence”.
`custom`	`yaml_unterminated_quoted_scalar` — “unterminated quoted scalar”.

XML (AssayXML)

Code	Meaning
`xml_bad_attribute_name`	Invalid attribute name.
`xml_bad_character_reference`	Invalid character reference.
`xml_bad_name`	Invalid name.
`xml_bad_pi_target`	Invalid processing instruction target.
`xml_entity_expansion_limit`	Entity expansion limit exceeded.
`xml_expected_equals`	Expected ‘=’ after attribute name.
`xml_external_dtd_ignored`	External DTD subset ignored (never fetched).
`xml_external_entity_ignored`	External entity ignored (never fetched).
`xml_mismatched_tag`	Closing tag does not match.
`xml_no_root`	Document has no root element.
`xml_raw_lt_in_attribute`	‘<’ is not allowed in an attribute value.
`xml_recursive_entity`	Entity &…; refers to itself. Params: `entity`.
`xml_root_mismatch`	Root element must be <…>, found <…>. Params: `expected`.
`xml_unclosed_element`	Element is never closed.
`xml_undeclared_entity`	Reference to an undeclared entity.
`xml_unquoted_attribute`	Attribute value must be quoted.
`xml_unterminated_attribute`	Unterminated attribute value.
`xml_unterminated_cdata`	Unterminated CDATA section.
`xml_unterminated_comment`	Unterminated comment.
`xml_unterminated_doctype`	Unterminated DOCTYPE.
`xml_unterminated_entity`	Unterminated entity reference.
`xml_unterminated_pi`	Unterminated processing instruction.
`xml_unterminated_tag`	Unterminated tag.