pyyaml 6.0.3: yaml.error.YAMLError

# PyYAML YAMLError exception hierarchy and handling

This sample pins `pyyaml` 6.0.3 and verifies `yaml.error.YAMLError` as the root exception class for all YAML parsing and processing errors.

The contract verifies:
- `yaml.error.YAMLError` is a base exception inheriting from standard `Exception` and is aliased at package top-level as `yaml.YAMLError`.
- `yaml.scanner.ScannerError` (malformed YAML tokens/mapping syntax) inherits from `yaml.error.MarkedYAMLError` and is caught by `except yaml.error.YAMLError`.
- `yaml.parser.ParserError` (unclosed flow collections and parsing anomalies) inherits from `yaml.error.MarkedYAMLError` and is caught by `except yaml.error.YAMLError`.
- `yaml.constructor.ConstructorError` (unrecognized custom tags) inherits from `yaml.error.MarkedYAMLError` and is caught by `except yaml.error.YAMLError`.
- `yaml.error.YAMLError` supports direct instantiation with custom error messages and serves as a base class for custom application-level YAML exception handling.

Clean-room public code sample — generation instructions

Write a brand-new, minimal, self-contained code sample in this clean-room directory.
Do not copy, paraphrase, or reference any existing project source. Work only from this spec.

A csx.json manifest scaffold already exists. Do not recreate it from memory. Preserve its case.goal, packages and symbols; fill its empty case.contract with exact assertions and correct its environment, commands and verifierAdapter for the files you generate.

Goal: verify yaml.error.YAMLError in pkg:pypi/pyyaml@6.0.3
Kind: HOW

Use EXACTLY these public packages and versions:
  - pkg:pypi/pyyaml@6.0.3
Demonstrate these symbols/APIs:
  - yaml.error.YAMLError

Rules:
  - One focused purpose; the smallest project that proves the goal.
  - Include a contract test (test/contract.*) that runs OFFLINE and exits 0 exactly when the goal behavior works.
  - Pin every dependency with a lockfile so resolution is reproducible.
  - No secrets, credentials, or tokens. No real URLs (only example.com or localhost). No absolute paths.
  - No personal names, emails, company names, or project identifiers of any kind.
  - No binaries and no generated output (node_modules, dist, target, venv, .git, .env).
  - Keep it under 200 files and 256KB packed.

{"case":{"caseId":"case:sha256:102957266350072468958aaf42b547673b11df9109c81e89517c13770d8d5e0c","contract":["yaml.error.YAMLError is the base exception class in PyYAML inheriting from Exception and aliased as yaml.YAMLError.","Parsing malformed YAML mapping syntax raises ScannerError, which is caught by except yaml.error.YAMLError.","Parsing unclosed flow collections raises ParserError, which is caught by except yaml.error.YAMLError.","Parsing unrecognized custom tags raises ConstructorError, which is caught by except yaml.error.YAMLError.","yaml.error.YAMLError can be directly instantiated with a message and subclassed for custom application error hierarchies."],"goal":"verify yaml.error.YAMLError in pkg:pypi/pyyaml@6.0.3","kind":"HOW","packages":["pkg:pypi/pyyaml@6.0.3"],"schemaVersion":1,"symbols":["yaml.error.YAMLError"]},"contractCommand":["python","test/contract.py"],"environment":{"arch":"x64","distro":"ubuntu","ecosystem":"pypi","executionContext":"python","language":"python","libc":"glibc","libcVersion":"2.39","os":"linux","osVersionBucket":"24","packageManager":"pip","runtime":"python","schemaVersion":1},"license":"MIT-0","packages":["pkg:pypi/pyyaml@6.0.3"],"schemaVersion":1,"subject":"pkg:pypi/pyyaml@6.0.3","symbols":["yaml.error.YAMLError"],"verifierAdapter":"python@1"}

pyyaml==6.0.3

{
  "schemaVersion": 1,
  "goal": "verify yaml.error.YAMLError in pkg:pypi/pyyaml@6.0.3",
  "kind": "HOW",
  "packages": [
    "pkg:pypi/pyyaml@6.0.3"
  ],
  "symbols": [
    "yaml.error.YAMLError"
  ]
}

import yaml
import yaml.error
import yaml.scanner
import yaml.parser
import yaml.constructor

# 1. Base exception inheritance and top-level alias
assert issubclass(yaml.error.YAMLError, Exception), "YAMLError must subclass Exception"
assert yaml.error.YAMLError is yaml.YAMLError, "yaml.error.YAMLError must be aliased as yaml.YAMLError"
assert issubclass(yaml.error.MarkedYAMLError, yaml.error.YAMLError), "MarkedYAMLError must subclass YAMLError"

# 2. ScannerError handling (syntax / mapping parsing failure)
try:
    yaml.safe_load("key: : value")
    raise AssertionError("expected ScannerError on invalid mapping syntax")
except yaml.error.YAMLError as exc:
    assert isinstance(exc, yaml.scanner.ScannerError), f"expected ScannerError, got {type(exc)}"
    assert isinstance(exc, yaml.error.MarkedYAMLError), "ScannerError must inherit from MarkedYAMLError"
    assert exc.problem is not None, "ScannerError must have a problem description"
    assert exc.problem_mark is not None, "ScannerError must have problem position mark"

# 3. ParserError handling (unclosed flow collection)
try:
    yaml.safe_load("{key: val,")
    raise AssertionError("expected ParserError on unclosed flow mapping")
except yaml.error.YAMLError as exc:
    assert isinstance(exc, yaml.parser.ParserError), f"expected ParserError, got {type(exc)}"
    assert isinstance(exc, yaml.error.MarkedYAMLError), "ParserError must inherit from MarkedYAMLError"
    assert exc.problem is not None, "ParserError must have a problem description"

# 4. ConstructorError handling (unsupported custom YAML tag)
try:
    yaml.safe_load("!unsupported_tag [1, 2, 3]")
    raise AssertionError("expected ConstructorError on unrecognized YAML tag")
except yaml.error.YAMLError as exc:
    assert isinstance(exc, yaml.constructor.ConstructorError), f"expected ConstructorError, got {type(exc)}"
    assert isinstance(exc, yaml.error.MarkedYAMLError), "ConstructorError must inherit from MarkedYAMLError"

# 5. Direct instantiation and custom application subclassing
err = yaml.error.YAMLError("custom configuration error")
assert str(err) == "custom configuration error"
assert isinstance(err, yaml.error.YAMLError)

class AppConfigYamlError(yaml.error.YAMLError):
    pass

try:
    raise AppConfigYamlError("custom app config failed")
except yaml.error.YAMLError as exc:
    assert isinstance(exc, AppConfigYamlError)
    assert str(exc) == "custom app config failed"

print("CONTRACT PASS: yaml.error.YAMLError verified offline")