YAML Null and Empty Values
Five spellings of null against the things routinely confused with it: empty strings, empty collections, and a key written with no value at all. Includes a sequence containing a hole, an empty string and two nulls in a row.
# Null and empty. YAML has several spellings of null and several things that are NOT null but
# are frequently confused with it. A config loader that treats them alike will happily accept a
# key it should have rejected.
explicit_null: null
tilde_null: ~
implicit_null:
upper_null: NULL
title_null: Null
tilde_in_string: "~"
empty_string: ""
empty_single_quoted: ''
empty_map: {}
empty_list: []
list_with_holes:
- first
-
- ""
- null
- ~
map_with_empty_values:
a:
b: ""
c: {}
after_empty_value: this key proves the empty value above terminated
Specifications
- Null Spellings
- 5
- Empty Collections
- 2
- Empty Strings
- 2
- Edge Case
- an omitted value is null, not an empty string
Testing contract
Expected to pass- Scenario
- Distinguish YAML null from an empty string and from an empty collection
- Expected result
- implicit_null, explicit_null, tilde_null, upper_null and title_null all load as null, while empty_string, empty_map and empty_list load as distinct non-null values
What is a .yaml file?
YAML (YAML Ain't Markup Language) is a human-readable data-serialization format using indentation, key-value pairs, and lists, and is a superset of JSON. It supports comments, anchors, and multiple documents per file, favoring readability for configuration. Its indentation sensitivity makes it error-prone to hand-edit.
How to use this file
Use an example YAML file to test config parsers, indentation and anchor handling, multi-document streams, and safe-loading to avoid arbitrary object construction.
How to use this file for testing
“YAML Null and Empty Values” is a deterministic Novus Examples fixture for Config parsing, Encoding detection, Editor testing. TOML and INI configuration files with nested sections and typed values — for testing config parsers and loaders.
Documented properties for this file: YAML · 564 bytes. Compare results against paired or grouped companions on this page when present (clean↔damaged, searchable↔scanned, or format twins) so scores stay reproducible across runs.
Download the file once, keep the path stable in CI or local scripts, and treat the spec table as the contract: dimensions, seeds, field lists, and roles are intentional. Corrupt or invalid samples are labelled as such — expect parsers to fail loudly rather than silently accept them.
Pipeline and infrastructure fixtures are inert configuration: steps reference fictional images and scripts, and nothing here executes. Run your linter, schema validator, migrator, or policy engine against them, and expect the deprecated-syntax and intentionally invalid variants to be rejected.
Point your config loader at the file and assert it reads the documented sections and typed values, including any deliberately-tricky nesting or comments.
Code examples
import yaml # pip install pyyaml
with open("null-and-empty.yaml") as f:
data = yaml.safe_load(f)
print(data)Related files
- yamlYAML Anchors and AliasesAnchors and aliases across mapping, sequence and scalar nodes, including an anchor nested inside another anchored node. The point most tooling misses: an alias is a reference to the same node, so a shallow-loading parser can share mutable state between jobs.
- yamlYAML Block Scalars and Chomping IndicatorsEvery block-scalar variation in one file: literal and folded styles, all three chomping indicators, an explicit indentation indicator, a folded block with a paragraph break, and an embedded shell-shaped script whose own indentation must survive.
- yamlYAML Bounded Anchor ReuseNested anchor reuse kept deliberately small: two anchors, six references, thirty-one expanded nodes. It is here to test alias resolution and expansion accounting on a safe input, and is explicitly not a billion-laughs expansion bomb.
- yamlYAML Directives and CommentsA two-document stream where each document declares its own %YAML directive and the second adds a %TAG handle used by a local tag. Comments appear in every position they are legal, and every one of them is lost by a non-round-tripping loader.
- yamlYAML Duplicate KeysDuplicate keys at three nesting levels, including a duplicated top-level sequence. The spec forbids them; most loaders keep the last silently, a few keep the first, and strict linters reject the document. The file publishes the last-wins answer.
- yamlYAML Explicit and Local TagsExplicit tags across the standard set — !!str, !!float, !!int, !!bool, !!null, !!binary, !!timestamp, !!omap, !!set — alongside two application-local ! tags. CI dialects use local tags in the wild, so a pipeline parser has to decide whether to reject, ignore, or resolve them.
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