Crate vastlint_core 

vastlint-core

A zero-I/O VAST XML validation library. Takes a VAST, VMAP, or DAAST XML string and returns a structured ValidationResult listing every issue found, the detected document type and VAST version, and a summary of error/warning/info counts. The document type is decided by the root element: <vmap:VMAP> runs the VMAP 1.0 rules (including full VAST validation of inline <vmap:VASTAdData> ad data) and <DAAST> runs the DAAST 1.0 rules.

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
• inspect_document – extract creative and wrapper metadata from one VAST XML document
• all_rules – list the full 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.

InspectDocumentMeta

InspectMediaFile

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.

DocumentType

The kind of IAB ad document that was validated.

InspectAdType

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.

Constants

VERSION

The version of this engine and of the rule catalog it carries.

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.

inspect_document

validate

Validate a VAST XML string using default settings.

validate_with_context

Validate a VAST XML string with caller-supplied context.