feat(fast-validator): add multi-error accumulation and RFC 6901 JSON pointer precision

[jonhealy1]

Summary

This PR resolves issues with vague error reporting during high-speed batch validation. Previously, fastjsonschema swallowed nested field paths behind generic top-level $ root errors when evaluating composite extension schemas (oneOf/anyOf). Additionally, the validation loop short-circuited on the first broken field, requiring multi-pass debugging across large batch jobs.

This release introduces multi-error accumulation, lazy branch unrolling, RFC 6901 JSON Pointer formatting, and multi-tier schema compilation to ensure 100% extension compatibility at full C-speed.

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Key Changes

• Multi-Error Accumulation (FastSTACMultiValidationError)

  • Refactored the FastValidator execution pass to evaluate the base schema and all active item extensions in a single run.
  • Collects every distinct field failure on an item into a container exception rather than aborting on the first error.

• RFC 6901 JSON Pointer Normalization (parse_json_pointer)

  • Translates fastjsonschema's internal CPython variable names (e.g., data['properties']['eo:cloud_cover'] and data.properties.sat:relative_orbit) into standard JSON Pointers (e.g., $.properties.eo:cloud_cover).

• Compile-Time Branch Unrolling (compile_unrolled_schema)

  • Pre-compiles oneOf/anyOf subschema branches independently to prevent fastjsonschema's internal try...except exception handling from discarding leaf-node field paths.
  • Unmasks exact failure locations without running fallback validation libraries on failing records.

• Resilient Multi-Tier Schema Patching

  • Updated optimize_schema_for_compiler() to strip restrictive additionalProperties: false flags from shared extension objects.
  • Prunes empty subschemas ({}) and draft-2020-12 conditional blocks that caused IndentationError or JsonSchemaDefinitionException skips on extensions like file/v2.1.0, product/v1.0.0, and storage/v2.0.0.

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Benchmark & Diagnostic Comparison

Before (v4.5.2):

❌ [Extension: https://stac-extensions.github.io/eo/v1.0.0/schema.json] Field '$': must be valid exactly by one definition (0 matches found)

After (v4.6.0):

❌ [Extension: https://stac-extensions.github.io/eo/v2.0.0/schema.json] Field '$.properties.eo:cloud_cover': must be smaller than or equal to 100
   Affected Items: 1
   Examples:       S2A_MSIL2A_20220217T183431_N0510_R027_T13VEK_20240516T022440

❌ [Extension: https://stac-extensions.github.io/sat/v1.1.0/schema.json] Field '$.properties.sat:relative_orbit': must be integer
   Affected Items: 1
   Examples:       S2A_MSIL2A_20220217T183431_N0510_R027_T13VEK_20240516T022440
Execution Overhead: Average execution time remains under ~0.35 ms per object (~3,000 items/sec) on batch runs.

[Copilot]

🔵 Needs a closer look

It changes core validation semantics by recursively stripping additionalProperties/unevaluatedProperties: false (silently weakening validation) and reworks error control flow, which warrants human review beyond the flagged stray artifact.

Pull request overview

This PR overhauls the --fast validator (fast_validator.py) to improve error reporting during high-speed batch validation. Instead of aborting on the first failure and surfacing generic $ root errors from fastjsonschema's oneOf/anyOf handling, it now accumulates all failures per item, attributes each to its schema source, and normalizes field paths into $.-style pointers. It also adds more aggressive schema patching so more community extensions compile under fastjsonschema without being skipped.

Changes:

• Adds parse_json_pointer, FastSTACValidationError, and FastSTACMultiValidationError, plus multi-error accumulation across base + all extension schemas in validator/run/run_dict/_validate_recursive.
• Adds compile_unrolled_schema (per-branch oneOf/anyOf compilation to recover exact field paths) and expands optimize_schema_for_compiler to strip additionalProperties/unevaluatedProperties: false, $comment, and prune empty subschemas.
• Bumps version to 4.6.0 (CHANGELOG + pyproject.toml), updates a test collection expectation to v1.1.0 schemas, removes a network-dependent test, and adds tests/test_error_reporting.py.

File summaries

File	Description
stac_validator/fast_validator.py	Core logic: JSON-pointer normalization, error classes, multi-error accumulation, branch unrolling, broader schema patching.
tests/test_error_reporting.py	New offline tests covering pointer parsing, error classes, oneOf unmasking, and multi-error accumulation.
tests/test_validate_item_collection.py	Updates expected schema versions to v1.1.0/projection v2.0.0; removes a remote paginated test.
test.json	Adds a 3089-line Sentinel-2 item at the repo root (appears to be a benchmarking/debug leftover).
pyproject.toml	Version bump 4.5.2 → 4.6.0.
CHANGELOG.md	Adds v4.6.0 release notes and compare links.

Review details

• Files reviewed: 5/6 changed files
• Comments generated: 2
• Review effort level: Balanced

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