Crate vastlint_core 

vastlint-core

A zero-I/O VAST XML validation library. Takes a VAST XML string and returns a structured ValidationResult listing every issue found, the detected VAST version, and a summary of error/warning/info counts.

The entire public surface is two functions and a handful of types:

• validate – validate with default settings (most callers want this)
• validate_with_context – validate with rule overrides or wrapper depth
• fix – fix deterministic issues and return repaired XML
• fix_with_context – fix with rule overrides or wrapper depth
• all_rules – list the full 118-rule catalog

Performance — allocator recommendation

vastlint-core builds an owned document tree on every call (one heap allocation per XML element, attribute, and text node). Under concurrent load the system allocator becomes a bottleneck because all threads compete for a shared free-list lock.

Switching to mimalloc in your binary crate eliminates this contention and gives dramatically better throughput at high concurrency, especially for larger documents:

# Cargo.toml (your binary, not a library crate)
[dependencies]
mimalloc = { version = "0.1", default-features = false }

// src/main.rs
use mimalloc::MiMalloc;
#[global_allocator]
static GLOBAL: MiMalloc = MiMalloc;

Measured on Apple M4 (10 threads, production-realistic VAST tags):

Allocator	17 KB tag	44 KB tag
system (default)	1,847 tags/s · 541 µs	328 tags/s · 3,048 µs
mimalloc	15,760 tags/s · 63 µs	2,635 tags/s · 380 µs

mimalloc: ~8× throughput improvement on multi-threaded workloads.

⚠️ Do not set a global allocator in a library crate — it would override the allocator for any host process that links you (Go, Python, Ruby runtimes, etc.), which can cause heap corruption.

Quick start

let xml = r#"<VAST version="2.0">
  <Ad><InLine>
    <AdSystem>Demo</AdSystem>
    <AdTitle>Ad</AdTitle>
    <Impression>https://t.example.com/imp</Impression>
    <Creatives>
      <Creative>
        <Linear>
          <Duration>00:00:15</Duration>
          <MediaFiles>
            <MediaFile delivery="progressive" type="video/mp4"
                       width="640" height="360">
              https://cdn.example.com/ad.mp4
            </MediaFile>
          </MediaFiles>
        </Linear>
      </Creative>
    </Creatives>
  </InLine></Ad>
</VAST>"#;

let result = vastlint_core::validate(xml);
assert_eq!(result.summary.errors, 0);

Design constraints

The library has no I/O, no logging, no global state, and no async runtime. It can be embedded in a CLI, HTTP server, WASM module, or FFI binding without pulling in any platform-specific dependencies.

Three crate dependencies: quick-xml (XML parsing), url (RFC 3986), and phf (compile-time hash maps).

Structs

AppliedFix

A single fix that was successfully applied to the document.

FixResult

The result of a fix or fix_with_context call.

Issue

A single validation finding.

RuleMeta

Metadata about a single rule, as exposed by the public catalog.

Summary

Counts of issues by severity.

ValidationContext

Context passed to validate_with_context. All fields have safe defaults.

ValidationResult

The full result of validating a VAST document.

Enums

DetectedVersion

How the version was determined.

RuleLevel

Per-rule severity override. Mirrors Severity but adds Off.

RuleSource

The external standard or authority that a rule is derived from.

Severity

Issue severity, based strictly on spec language.

VastVersion

The VAST version as declared in the version attribute or inferred from document structure.

Functions

all_rules

Returns the full catalog of known rules in definition order.

fix

Fix a VAST XML string using default settings.

fix_with_context

Fix a VAST XML string with caller-supplied context.

validate

Validate a VAST XML string using default settings.

validate_with_context

Validate a VAST XML string with caller-supplied context.