YAML Anchors and Aliases
Anchors 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.
# Anchors (&name) and aliases (*name). An alias is a REFERENCE to the same node, not a copy:
# after loading, `jobs.build` and `jobs.test` may be the identical object, so mutating one
# mutates the other unless the loader deep-copies. Round-tripping usually loses the anchors
# entirely and writes the value out three times.
defaults: &defaults
image: registry.example.invalid/ci/runner:1.4
retries: 2
timeout: 30
artifacts: &artifacts
- build/
- dist/
release_tag: &tag v1.4.0
jobs:
build: *defaults
test: *defaults
package: *defaults
collect:
build: *artifacts
test: *artifacts
annotations:
version: *tag
built_from: *tag
nested:
outer: &outer
inner: &inner
leaf: value
sibling: *inner
copy: *outer
Specifications
- Anchors
- 5
- Alias References
- 9
- Nested Anchors
- 2
- Edge Case
- an alias is a reference to the same node, not a copy
Testing contract
Expected to pass- Scenario
- Load a document whose aliases reference the same node from several places
- Expected result
- All nine alias references resolve, and a loader that shares nodes reports jobs.build and jobs.test as the identical object rather than as two equal copies
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 Anchors and Aliases” 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 · 749 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("anchors-and-aliases.yaml") as f:
data = yaml.safe_load(f)
print(data)Related files
- 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.
- yamlYAML Flow and Block StylesFlow (JSON-like) and block collections expressing the same structures, nested inside one another in both directions, plus a flow mapping wrapped across lines and a line of strict JSON — which is valid YAML, and a useful check on a parser's JSON-subset claim.
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