zemdomu

ZemDomu Core

Semantic accessibility static analysis with supported component context.

ZemDomu is static analysis for semantic HTML and accessibility across supported HTML, React, and Vue component structures. Its differentiated definition is static analysis for semantic HTML architecture across component-based applications. ZemDomu Core is the shared engine behind the ZemDomu CLI, ZemDomu VS Code Extension, and ZemDomu GitHub Action.

Core analyzes supported HTML, JSX, TSX, and Vue source patterns. Project-aware analysis can find named structural problems across statically resolvable React and Vue imports. It does not model every runtime state or establish accessibility or WCAG conformance.

Quick start: scan your source

Requires Node.js 22.17 or newer.

Run ZemDomu without a global install. The command exits with 1 when it finds diagnostics, which makes the same check useful locally and in CI.

npx zemdomu check "src/**/*.{html,jsx,tsx,vue}" --format pretty

Pretty output points to the authoring source and includes a stable rule code:

Card.tsx:3:5 ZMD004: <img> tag missing alt attribute

What It Is

ZemDomu Core is the semantic accessibility static-analysis engine for modern frontend codebases. It helps developers catch issues like missing landmarks, confusing heading structure, unlabeled controls, weak semantic relationships, and cross-component composition problems before those issues become late-stage audit findings.

This package provides the shared logic used by:

• the ZemDomu CLI
• the ZemDomu VS Code Extension
• the ZemDomu GitHub Action

Why ZemDomu

ZemDomu complements file-oriented source linters and rendered-DOM testing with one focused source model across supported frontend syntax.

• Cross-component analysis finds supported structural issues that only appear when statically resolvable components are composed.
• One shared rules engine powers editor, CLI, and CI behavior consistently.
• Diagnostics focus on semantic HTML, accessible naming, and document structure.
• Custom-rule support lets teams extend checks without rebuilding a lint stack.

Features

• Lint semantic issues in HTML, JSX, TSX, and Vue templates.
• Works in Node.js 22.17 or newer, locally and in CI.
• Extensible rule system with simple custom rules.
• Cross-component analysis for React/JSX and Vue projects.
• Command line interface with --custom and --cross.
• Configurable rule severity (error, warning, off).
• Performance diagnostics for profiling lint runs.
• Simple API: lint(content, options).

Library installation

npm install zemdomu
# or
yarn add zemdomu

Usage

import { lint } from "zemdomu";

const html = "<img>";
const results = lint(html, { rules: { requireAltText: true } });

console.log(results);
// [
//   {
//     line: 0,
//     column: 0,
//     message: "<img> tag missing alt attribute",
//     rule: "requireAltText"
//   }
// ]

How ZemDomu fits

ZemDomu is one layer in an accessibility testing strategy, not a conformance claim or a replacement for rendered and manual testing.

• axe-core tests rendered web UI; ZemDomu checks supported source and component relationships earlier. Use both layers.
• eslint-plugin-jsx-a11y is established static JSX linting in ESLint; ZemDomu uses one engine across HTML, React, and Vue with supported cross-file relationships.
• Nu Html Checker checks HTML, CSS, and SVG documents for standards-related mistakes; ZemDomu focuses on named semantic accessibility rules in application source.

Comparison source matrix reviewed 2026-08-30; linked primary documentation reverified 2026-09-04.

API

lint(content: string, options?: LinterOptions): LintResult[]

Supported package entry point

Import public APIs only from the package root, zemdomu. Use lint() for one in-memory source and ProjectLinter for file or project analysis. Subpath imports such as zemdomu/linter are deprecated compatibility paths and can be removed in the next major release.

import { lint, ProjectLinter } from "zemdomu";

const inMemoryResults = lint(source, { filePath: "src/Card.tsx" });
const project = new ProjectLinter({ crossComponentAnalysis: true });
const projectResults = await project.lintFiles(["src/Card.tsx"]);
const semanticGraph = await project.buildSemanticGraph(["src/Card.tsx"]);
const pageModel = await project.buildPageModel(["src/AppLayout.tsx"]);
const pageDiagnostics = await project.lintPageDiagnostics(["src/AppLayout.tsx"]);

buildSemanticGraph() follows supported local React/JSX/TSX and Vue imports and returns the public schema 1.0 graph. IDs and array order are deterministic for the same project inputs. Source-backed files, components, imports, composition usages, headings, navigation landmarks, list items, sections, and static document IDs retain zero-based locations. Each component also exposes a semanticOutput: a single unconditional native root is inferred with an ordered component evidence path and the certain native source location. Transitive wrappers can inherit that output, while conditional returns, fragments, children/slots, multiple roots, unresolved imports, cycles, configured depth limits, and unknown route identity remain explicit unknown or boundary states.

buildPageModel() composes graph output into page-scoped component trees and ordered heading, landmark, section, navigation, and document-ID facts. Supply pages: [{ route, entryFile }] for certain route identity, or opt into createReactFileRouteAdapter() / createVueFileRouteAdapter() for inferred filesystem conventions. Custom adapters implement SemanticRouteAdapter, so the graph and page model do not hard-code a router. With no applicable adapter, entry roots and route identity remain explicit unknowns.

lintPageDiagnostics() returns canonical diagnostics and adds the affected page, readable component path, composition-instance source locations, and a preferred edit location when a page/path is statically resolved. The existing singleH1 rule remains an at-most-one rule. The page-only advisory requirePageH1 rule (ZMD022) checks for a missing page H1 only when explicitly enabled with rules: { requirePageH1: "warning" }. Conservative suggestion text is limited to structural rules with a supported edit direction. Conditional output and unresolved imports, slots, runtime composition, cycles, and depth boundaries suppress absence and collision claims that are not statically certain. Use formatZemDomuDiagnosticPretty() to render this optional context for terminal output.

Parameters

• content: HTML, JSX, TSX, or Vue template string input.
• options.rules: severity settings for built-in rules.
• options.customRules: array of additional rules.
• options.filePath: optional source file path.
• options.forceHtml: treat input as HTML.
• options.perf: attach a PerformanceRecorder instance.

Example LinterOptions

interface LinterOptions {
  rules?: Record<string, "error" | "warning" | "off">;
  customRules?: Rule[];
  filePath?: string;
  forceHtml?: boolean;
  perf?: PerformanceRecorder;
}

Example enabling rule severities:

const results = lint(html, {
  rules: { requireAltText: "warning", uniqueIds: "error" }
});

Example LintResult

interface LintResult {
  line: number;
  column: number;
  message: string;
  rule: string;
}

Canonical diagnostics

LintResult remains the compatibility shape returned by lint() and ProjectLinter; its code, severity, and filePath fields can be absent for legacy and custom-rule results. Integrations that need a stable machine-readable contract should adapt results with toZemDomuDiagnostic() and serialize them with serializeZemDomuDiagnostics().

import {
  lint,
  serializeZemDomuDiagnostics,
  toZemDomuDiagnostic,
} from "zemdomu";

const results = lint(source, { filePath: "src/Card.tsx" });
const diagnostics = results.map((result) =>
  toZemDomuDiagnostic(result, { sourceFile: "src/Card.tsx" })
);
console.log(serializeZemDomuDiagnostics(diagnostics, 2));

Every ZemDomuDiagnostic has schemaVersion, rule, code, severity, message, and a source file/line/column. Lines and columns are zero-based, as they are in LintResult. Page identity, component path, related locations, preferred edit location, suggestions, provenance, and confidence are optional. Schema 1.0 uses the rule name as the code fallback for parse errors or custom rules that do not provide a registered or explicit code. Missing legacy severity defaults to error; pass defaultSeverity when another canonical severity is appropriate. When present, confidence is one of certain, inferred, or unknown. The adapter requires result.filePath or context.sourceFile and throws if neither is available. It does not mutate the legacy result.

CLI Usage

Run the linter from the command line by installing the package globally or by using npx. Provide one or more glob patterns to specify the files to lint. Patterns may be separated by spaces, commas, or newlines; commas inside brace expressions remain part of the pattern. Discovery accepts either path separator, deduplicates and sorts matches, and excludes hidden files, node_modules, directories, and symlink traversal.

npx zemdomu "src/**/*.{html,jsx,tsx,vue}" --custom my-rule.js
npx zemdomu "src/**/*.html,src/**/*.jsx"

Use --custom (or -c) to provide a path to a JavaScript or TypeScript module exporting a custom rule or array of rules. For safety, the CLI only accepts files inside a ./custom-rules directory relative to your current working directory. You can repeat --custom to load multiple rule files.

Use --cross to enable cross-component analysis.

Use --perf to emit a JSON timing report to stdout, and --perf-slowest to also print the slowest file and phase.

Output formats and exit codes

zemdomu check accepts the same file patterns as the existing command and can write one of three equivalent views of the canonical diagnostic contract:

zemdomu check "src/**/*.{html,jsx,tsx,vue}" --format pretty
zemdomu check "src/**/*.{html,jsx,tsx,vue}" --format json
zemdomu check "src/**/*.{html,jsx,tsx,vue}" --format sarif

pretty is the default and writes readable diagnostics to stderr. json and sarif write only their machine-readable JSON document to stdout; operational and invocation errors always go to stderr. JSON contains a deterministic, source-sorted array of schema 1.0 ZemDomuDiagnostic objects. SARIF uses version 2.1.0, maps canonical related locations to SARIF relatedLocations, and stores page/component-path context in structured SARIF properties rather than adding presentation text to the diagnostic message.

The CLI exits with 0 when no diagnostics are emitted, 1 when it emits one or more diagnostics, and 2 for invalid CLI usage. --perf and --perf-slowest are only available with --format pretty so machine output is never mixed with timing output.

Semantic graph and page inspection

Use graph to inspect the deterministic semantic graph for one or more entry files. The command follows supported local React, JSX, TSX, and Vue imports and groups source files, components, rendered semantic nodes, and explicit unknown analysis boundaries in readable sections.

zemdomu graph "src/AppLayout.tsx"
zemdomu graph "src/pages/**/*.{tsx,vue}" --cross-depth 4

Use inspect to compose one route from an explicit entry file. Requiring the route-to-entry mapping keeps router conventions outside Core and makes the result reproducible:

zemdomu inspect "/products/[id]" --entry "src/AppLayout.tsx"

Page inspection prints the nested component path, ordered semantic facts, source locations, and any unresolved or traversal-boundary unknowns. Both inspection commands write human-readable output to stdout and exit with 2 for invalid invocations or unmatched entry files. Machine-readable inspection output is not part of this command contract; use the public ProjectLinter.buildSemanticGraph() and buildPageModel() APIs when structured data is required.

Cross-Component Analysis

When analyzing JSX or Vue projects you can track semantic issues across component boundaries. Instantiate ProjectLinter with the crossComponentAnalysis option or pass --cross to the CLI. Use crossComponentDepth or --cross-depth to limit how deep component trees are traversed during analysis.

import { ProjectLinter } from "zemdomu";

const linter = new ProjectLinter({
  crossComponentAnalysis: true,
  crossComponentDepth: 2,
});

await linter.lintFile("App.jsx");

npx zemdomu "src/**/*.{jsx,tsx,vue}" --cross --cross-depth 2

Performance Diagnostics

Attach a PerformanceDiagnostics recorder to gather timing information for each file and rule.

import { lint, PerformanceDiagnostics } from "zemdomu";

const perf = new PerformanceDiagnostics();
lint(code, { perf });
console.log(perf.getAsJSON());

Writing Custom Rules

Custom rules are simple objects implementing the Rule interface. At minimum, provide a name, a test function that returns true when a node violates the rule, and a message describing the problem.

interface Rule {
  name: string;
  test(node: any): boolean;
  message: string;
}

// my-rule.js
module.exports = {
  name: "noFooDiv",
  test: node => node.type === "element" && node.tagName === "foo",
  message: "<foo> is not allowed"
};

Use it programmatically:

import { lint } from "zemdomu";

const results = lint("<foo></foo>", { customRules: [require("./my-rule")] });

Helper Utilities

For more advanced rules you may need direct access to the parsed HTML or JSX AST. ZemDomu exposes helpers for traversal and attribute inspection:

import {
  parseHtml,
  visitHtml,
  getAttr,
  getJsxAttr,
  getJsxAttribute,
  getJsxAttributeState,
  getJsxExpressionState,
  getTag,
  isJsxExpressionPossiblyEmpty,
  ElementNode,
  HtmlVisitor,
} from "zemdomu";

Or via the CLI:

mkdir -p custom-rules
cp my-rule.js custom-rules/my-rule.js
npx zemdomu file.html --custom custom-rules/my-rule.js
npx zemdomu "src/**/*.{html,jsx,tsx,vue}" --perf --perf-slowest

There is a sample rule in custom-rules/example-rule.js that you can copy and edit.

Local Development

From the core package:

cd packages/ZemDomu-Core
npm install
npm run build

Links

• npm package: https://www.npmjs.com/package/zemdomu
• Website: https://zemdomu.dev/
• Issues and suggestions: https://github.com/ZemDomu/ZemDomu-core/issues
• VS Code extension: https://marketplace.visualstudio.com/items?itemName=ZachariasErydBerlin.zemdomu
• GitHub Action: https://github.com/ZemDomu/ZemDomu-action

License

ZemDomu Core is open source under the MIT License.

Copyright (c) 2025 Zacharias Eryd Berlin