feat(xml/unstable): add XML parsing and serialization module

.github/workflows/title.yml

@@ -76,4 +76,5 @@ jobs:
             ulid(/unstable)?
             uuid(/unstable)?
             webgpu(/unstable)?
+            xml(/unstable)?
             yaml(/unstable)?

browser-compat.tsconfig.json

@@ -48,6 +48,7 @@
     "./ulid",
     "./uuid",
     "./webgpu",
+    "./xml",
     "./yaml"
   ]
 }

deno.json

@@ -39,7 +39,8 @@
     "_tools/node_test_runner",
     "http/testdata",
     "fs/testdata",
-    "dotenv/testdata"
+    "dotenv/testdata",
+    "xml/testdata"
   ],
   "lint": {
     "rules": {
@@ -94,6 +95,7 @@
     "./ulid",
     "./uuid",
     "./webgpu",
+    "./xml",
     "./yaml"
   ]
 }

import_map.json

@@ -5,7 +5,6 @@
     "npm:/typescript": "npm:[email protected]",
     "automation/": "https://raw.githubusercontent.com/denoland/automation/0.10.0/",
     "graphviz": "npm:node-graphviz@^0.1.1",
-
     "@std/assert": "jsr:@std/assert@^1.0.16",
     "@std/async": "jsr:@std/async@^1.0.16",
     "@std/bytes": "jsr:@std/bytes@^1.0.6",
@@ -46,6 +45,7 @@
     "@std/ulid": "jsr:@std/ulid@^1.0.0",
     "@std/uuid": "jsr:@std/uuid@^1.1.0",
     "@std/webgpu": "jsr:@std/webgpu@^0.224.9",
+    "@std/xml": "jsr:@std/xml@^0.0.1",
     "@std/yaml": "jsr:@std/yaml@^1.0.10"
   }
 }

xml/_common.ts

@@ -0,0 +1,66 @@
+// Copyright 2018-2026 the Deno authors. MIT license.
+// This module is browser compatible.
+
+/**
+ * Internal shared utilities for the XML module.
+ *
+ * @module
+ */
+
+import type { XmlName } from "./types.ts";
+
+/**
+ * Line ending normalization pattern per XML 1.0 §2.11.
+ * Converts \r\n and standalone \r to \n.
+ */
+export const LINE_ENDING_RE = /\r\n?/g;
+
+/**
+ * Whitespace-only test per XML 1.0 §2.3.
+ * Uses explicit [ \t\r\n] instead of \s to match XML spec exactly:
+ *   S ::= (#x20 | #x9 | #xD | #xA)+
+ */
+export const WHITESPACE_ONLY_RE = /^[ \t\r\n]*$/;
+
+/**
+ * XML declaration version attribute pattern.
+ * Matches both single and double quoted values.
+ */
+export const VERSION_RE = /version\s*=\s*(?:"([^"]+)"|'([^']+)')/;
+
+/**
+ * XML declaration encoding attribute pattern.
+ * Matches both single and double quoted values.
+ */
+export const ENCODING_RE = /encoding\s*=\s*(?:"([^"]+)"|'([^']+)')/;
+
+/**
+ * XML declaration standalone attribute pattern.
+ * Matches both single and double quoted values, restricted to "yes" or "no".
+ */
+export const STANDALONE_RE = /standalone\s*=\s*(?:"(yes|no)"|'(yes|no)')/;
+
+/**
+ * Parses a qualified XML name into its prefix and local parts.
+ *
+ * @example Usage
+ * ```ts
+ * import { parseName } from "./_common.ts";
+ *
+ * parseName("ns:element"); // { prefix: "ns", local: "element" }
+ * parseName("element");    // { local: "element" }
+ * ```
+ *
+ * @param name The raw name string (e.g., "ns:element" or "element")
+ * @returns An XmlName object with local and optional prefix
+ */
+export function parseName(name: string): XmlName {
+  const colonIndex = name.indexOf(":");
+  if (colonIndex === -1) {
+    return { local: name };
+  }
+  return {
+    prefix: name.slice(0, colonIndex),
+    local: name.slice(colonIndex + 1),
+  };
+}

xml/_entities.ts

@@ -0,0 +1,178 @@
+// Copyright 2018-2026 the Deno authors. MIT license.
+// This module is browser compatible.
+
+/**
+ * Internal module for XML entity encoding and decoding.
+ *
+ * @module
+ */
+
+/**
+ * The five predefined XML entities per XML 1.0 §4.6.
+ * Using const assertion for precise typing.
+ */
+const NAMED_ENTITIES = {
+  lt: "<",
+  gt: ">",
+  amp: "&",
+  apos: "'",
+  quot: '"',
+} as const;
+
+/**
+ * Reverse mapping for encoding special characters.
+ */
+const CHAR_TO_ENTITY = {
+  "<": "&lt;",
+  ">": "&gt;",
+  "&": "&amp;",
+  "'": "&apos;",
+  '"': "&quot;",
+} as const;
+
+/**
+ * Extended mapping for attribute value encoding (includes whitespace).
+ */
+const ATTR_CHAR_MAP: Record<string, string> = {
+  "<": "&lt;",
+  ">": "&gt;",
+  "&": "&amp;",
+  "'": "&apos;",
+  '"': "&quot;",
+  "\t": "&#9;",
+  "\n": "&#10;",
+  "\r": "&#13;",
+};
+
+// Hoisted regex patterns for performance
+const ENTITY_RE = /&([a-zA-Z]+|#[0-9]+|#x[0-9a-fA-F]+);/g;
+const SPECIAL_CHARS_RE = /[<>&'"]/g;
+const ATTR_ENCODE_RE = /[<>&'"\t\n\r]/g;
+
+/**
+ * Pattern to detect bare `&` not followed by a valid reference.
+ * Valid references are: &name; or &#digits; or &#xhexdigits;
+ */
+const BARE_AMPERSAND_RE = /&(?![a-zA-Z][a-zA-Z0-9]*;|#[0-9]+;|#x[0-9a-fA-F]+;)/;
+
+/**
+ * Checks if a code point is a valid XML 1.0 Char per §2.2.
+ *
+ * Per the specification:
+ *   Char ::= #x9 | #xA | #xD | [#x20-#xD7FF] | [#xE000-#xFFFD] | [#x10000-#x10FFFF]
+ *
+ * This excludes:
+ * - NULL (#x0)
+ * - Control characters #x1-#x8, #xB-#xC, #xE-#x1F
+ * - Surrogate pairs #xD800-#xDFFF (handled separately)
+ * - Non-characters #xFFFE-#xFFFF
+ *
+ * @see {@link https://www.w3.org/TR/xml/#charsets | XML 1.0 §2.2 Characters}
+ */
+function isValidXmlChar(codePoint: number): boolean {
+  return (
+    codePoint === 0x9 ||
+    codePoint === 0xA ||
+    codePoint === 0xD ||
+    (codePoint >= 0x20 && codePoint <= 0xD7FF) ||
+    (codePoint >= 0xE000 && codePoint <= 0xFFFD) ||
+    (codePoint >= 0x10000 && codePoint <= 0x10FFFF)
+  );
+}
+
+/**
+ * Options for entity decoding.
+ */
+export interface DecodeEntityOptions {
+  /**
+   * If true, throws an error on invalid bare `&` characters.
+   * Per XML 1.0 §3.1, `&` must be escaped as `&amp;` unless it starts
+   * a valid entity or character reference.
+   *
+   * @default false
+   */
+  readonly strict?: boolean;
+}
+
+/**
+ * Decodes XML entities in a string.
+ *
+ * Handles the five predefined entities (§4.6) and numeric character
+ * references (§4.1) per the XML 1.0 specification.
+ *
+ * @param text The text containing XML entities to decode.
+ * @param options Decoding options.
+ * @returns The text with entities decoded.
+ */
+export function decodeEntities(
+  text: string,
+  options?: DecodeEntityOptions,
+): string {
+  // Fast path: no ampersand means no entities to decode
+  if (!text.includes("&")) return text;
+
+  if (options?.strict) {
+    const match = BARE_AMPERSAND_RE.exec(text);
+    if (match) {
+      throw new Error(
+        `Invalid bare '&' at position ${match.index}: ` +
+          `entity references must be &name; or &#num; or &#xHex;`,
+      );
+    }
+  }
+
+  return text.replace(ENTITY_RE, (match, entity: string) => {
+    if (entity.startsWith("#x")) {
+      // Hexadecimal character reference
+      const codePoint = parseInt(entity.slice(2), 16);
+      // Invalid per XML 1.0 §4.1 WFC: Legal Character - must match Char production
+      if (!isValidXmlChar(codePoint)) {
+        return match;
+      }
+      return String.fromCodePoint(codePoint);
+    }
+    if (entity.startsWith("#")) {
+      // Decimal character reference
+      const codePoint = parseInt(entity.slice(1), 10);
+      // Invalid per XML 1.0 §4.1 WFC: Legal Character - must match Char production
+      if (!isValidXmlChar(codePoint)) {
+        return match;
+      }
+      return String.fromCodePoint(codePoint);
+    }
+    // Named entity
+    if (entity in NAMED_ENTITIES) {
+      return NAMED_ENTITIES[entity as keyof typeof NAMED_ENTITIES];
+    }
+    // Unknown entity - return as-is
+    return match;
+  });
+}
+
+/**
+ * Encodes special characters as XML entities.
+ *
+ * @param text The text to encode.
+ * @returns The text with special characters encoded as entities.
+ */
+export function encodeEntities(text: string): string {
+  // Fast path: no special characters means nothing to encode
+  if (!/[<>&'"]/.test(text)) return text;
+  return text.replace(
+    SPECIAL_CHARS_RE,
+    (char) => CHAR_TO_ENTITY[char as keyof typeof CHAR_TO_ENTITY],
+  );
+}
+
+/**
+ * Encodes special characters for use in XML attribute values.
+ * Encodes whitespace characters that would be normalized per XML 1.0 §3.3.3.
+ *
+ * @param value The attribute value to encode.
+ * @returns The encoded attribute value.
+ */
+export function encodeAttributeValue(value: string): string {
+  // Fast path: no special characters means nothing to encode
+  if (!/[<>&'"\t\n\r]/.test(value)) return value;
+  return value.replace(ATTR_ENCODE_RE, (c) => ATTR_CHAR_MAP[c]!);
+}