226 lines
10 KiB
Markdown
226 lines
10 KiB
Markdown
# PureXML
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[](https://github.com/mihaelamj/PureXML/actions/workflows/style.yml)
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[](https://github.com/mihaelamj/PureXML/actions/workflows/swift-macos.yml)
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[](https://github.com/mihaelamj/PureXML/actions/workflows/swift-linux.yml)
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[](https://github.com/mihaelamj/PureXML/actions/workflows/swift-windows.yml)
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[](https://github.com/mihaelamj/PureXML/actions/workflows/swift-wasm.yml)
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[](LICENSE)
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PureXML is a dependency-free XML package written entirely in Swift.
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The goal is a Linux-, Windows-, and WebAssembly-compatible XML reader/writer that
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does not pull in `libxml2`, `expat`, or Foundation's `XMLParser`. The package is
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intentionally strict about portability:
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- no external SwiftPM dependencies
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- no bundled C sources
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- no Foundation requirement in the library target
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- root Swift package layout
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- macOS, Linux, Windows, and WASI build gates
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It is a sibling project to [PureYAML](https://github.com/mihaelamj/PureYAML) and
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follows the same structure, rules, and verification gates.
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## Roadmap
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The roadmap uses the TileDown Mermaid palette: green for shipped work, yellow for
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review, purple for epic grouping, and gray for open work.
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```mermaid
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flowchart TB
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classDef done fill:#ddf9e4,stroke:#34c759,color:#111827
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classDef review fill:#fff7d6,stroke:#ffcc00,color:#111827
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classDef epic fill:#f2e5ff,stroke:#af52de,color:#111827
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classDef todo fill:#f2f4f7,stroke:#8e8e93,color:#111827
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LDone["In main now"]:::done
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LReview["PR in review"]:::review
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LEpic["Epic grouping"]:::epic
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LTodo["Open issue, no PR"]:::todo
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Core["Core shipped: #1 push, #19 SAX, #28 encoding, #29 entities, #31 tree, #32 writer, #33 reader, #34 save, #35 chars"]:::done
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Query["Query + validation shipped: #21 #22 #23 query, #30 regex, #2 XSD/RELAX NG, #25 Schematron"]:::done
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Transform["Transform + HTML shipped: #3 XSLT, #20 HTML, #24 XInclude, #26 C14N, #27 Catalog"]:::done
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Parity["Parity completion shipped: #61 (XSLT keys/output, XSD union/import/identity, RELAX NG compact, HTML5 doc structure, C14N 2.0 trim)"]:::done
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Validator["Validation framework + recovering reader shipped: #92 (one located severity-aware ValidationError, never-crash read)"]:::done
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Editor["Editor integration shipped: #94 (source spans, unified lint, schema completions, structured quick-fixes)"]:::done
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Conformance["Conformance push shipped: DTD #72 #73, XSD #75 #76 #77 #78, parsing #95 #96 #98 #100, regex #89"]:::done
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LDone --> LReview
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LReview --> LEpic
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LEpic --> LTodo
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LTodo --> Core
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Core --> Query
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Query --> Transform
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Transform --> Parity
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Parity --> Validator
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Validator --> Editor
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Editor --> Conformance
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```
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The goal is full libxml2 feature parity in pure Swift with zero dependencies, by
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clean-room reimplementation (behavior reproduced from the private PureXML-research
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analysis, no upstream source copied). The streaming core, the schema languages
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(DTD, XSD, RELAX NG, Schematron), XPath 1.0, and the transform/canonicalization
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stack are shipped; the remaining depth gaps are tracked under epic #71. Deliberate
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non-goals: network
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fetching (`nanohttp`/`nanoftp`) and the threading/memory infrastructure stay out,
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and external resolution is opt-in through an injected resolver so XXE stays closed.
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The original epics, the documented-subset parity work (#61), the validation
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framework and recovering reader (#92), and the editor-integration layer (#94)
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are all shipped (summarized above). The remaining work is the depth gaps versus
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libxml2 a read-only conformance audit surfaced (#71):
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```mermaid
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flowchart TB
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classDef done fill:#ddf9e4,stroke:#34c759,color:#111827
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classDef review fill:#fff7d6,stroke:#ffcc00,color:#111827
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classDef epic fill:#f2e5ff,stroke:#af52de,color:#111827
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classDef todo fill:#f2f4f7,stroke:#8e8e93,color:#111827
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Epic71["#71 Beyond-parity libxml2 audit"]:::epic
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AuditDone["Closed in main: DTD #72 #73, XSD #75 #76 #77 #78, parsing #95 #96 #98 #100, regex #89, catalog #86"]:::done
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Epic74["#74 Parser-breadth sub-epic: standalone/decl #95, XML 1.1 #96, reader #98, recovery #100 done; encodings #97 #99 open"]:::epic
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Partial["Partial in main: RELAX NG #79, Schematron #80, XInclude #87, XPath/XPointer #88, DOM #90, serialization #91"]:::todo
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Open["Open: XSLT #81 #82, HTML5 #83 #84, C14N #85, encoding tables #97 #99, validator decomposition #101"]:::todo
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Epic71 --> AuditDone
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AuditDone --> Epic74
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Epic74 --> Partial
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Partial --> Open
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```
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## Status
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PureXML is a working, dependency-free XML library today: parse, emit, validate,
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query, and stream documents on macOS, Linux, Windows, and WASM. The test suite
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currently runs **606 tests in 90 suites** (`swift test`).
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### Shipped (libxml2-aligned surface)
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- **Model** (`PureXML.Model`): `Node`, `Element`, `Attribute`, `QualifiedName`,
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and a mutable `TreeNode` for in-place editing (insert, remove, replace, copy,
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parent navigation).
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- **Parsing** (`PureXML.Parsing`): iterative streaming parser over strings,
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bytes, or incremental character/byte sources. Pull events via `EventReader`,
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SAX2-style callbacks via `SAXHandler`, and a pull cursor via `TextReader`
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(libxml2 `xmlTextReader`). Handles elements, attributes, text, predefined and
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numeric entities, comments, CDATA, and processing instructions. Namespace
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bindings (`xmlns`) are resolved to URIs on parse.
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- **Encoding**: UTF-8/16/32 (with BOM sniffing), ISO-8859-1, and Windows-1252
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from raw bytes or streaming byte input.
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- **DTD (opt-in)**: `<!DOCTYPE>` is **off by default** (`Limits.allowDoctype:
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false`) to keep XXE and entity-expansion closed. When enabled, the internal
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subset is parsed; internal general entities expand with a bounded cap; external
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entities and external subsets are refused unless an injected
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`EntityResolver` supplies replacement text.
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- **Validation** (`PureXML.Validation`): one composable framework (the OpenAPIKit
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idiom, parameterized over subject and document) backing structural checks, **DTD
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validation** (content models, attribute lists/defaulting, tokenized types,
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ID/IDREF), **XSD** (datatypes, complex types, derivation control, wildcards,
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namespace qualification), **RELAX NG** (XML and compact syntax), and
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**Schematron** (rules, phases, dynamic messages). Errors are located by coding
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path for editor use.
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- **Emitting** (`PureXML.Emitting`): `Serializer` (save options, quote style,
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`xml:space`, line endings) and an incremental, namespace-aware `Writer` (libxml2
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`xmlTextWriter`) with compact and pretty modes.
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- **XPath / XPointer** (`PureXML.XPath`): XPath 1.0 (all axes, the core function
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library, eval-time namespace bindings) and XPointer (`element()`, `xpointer()`,
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`xpath1()`, `xmlns()`).
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### Safe defaults
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By default the parser rejects `<!DOCTYPE>` and refuses every external reference
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(`EntityResolver.refusing`). Enable DTD processing only when you need internal
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subset validation or internal entities, and wire a resolver only for trusted,
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in-memory replacements. Network fetching (`nanohttp`/`nanoftp`) and libxml2's
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threading/memory infrastructure are deliberate non-goals.
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### Remaining toward full libxml2 feature parity
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The original parity epics (the core I/O stack, query, transform, the schema
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languages, the validation framework, and editor integration) are all shipped. The
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remaining work is the depth gaps a read-only conformance audit surfaced, tracked
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under epic **#71** (and its parser-breadth sub-epic **#74**):
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| Open work | Issues | What it adds |
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|---|---|---|
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| XSLT 1.0 breadth | #81 #82 | Missing top-level elements and functions, html output |
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| HTML5 | #83 #84 | Full tree construction, tokenizer states, entity table |
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| C14N | #85 | Node-subset canonicalization, `xml:*` inheritance, 2.0 prefix rewrite |
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| Legacy encodings | #97 #99 | Single-byte and CJK multi-byte to-Unicode tables |
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| Validator decomposition | #101 | Inner XSD/DTD validators as composable rules |
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| Partial follow-ups | #79 #80 #86 #87 #88 #90 #91 | Remaining bullets on already-advanced areas |
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Each open issue carries a checklist of done vs remaining bullets. The encoding
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tables (#97, #99) are deferred until they can be vendored from authoritative
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Unicode mapping files rather than transcribed.
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## Usage
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```swift
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import PureXML
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// Build a tree and emit it (works today).
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let element = PureXML.Model.Element(
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"book",
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attributes: [.init("id", "bk101")],
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children: [.element(.init("title", children: [.text("XML Developer's Guide")]))],
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)
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let xml = PureXML.serialize(.element(element))
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try PureXML.validate(.element(element))
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// Parse it back into a tree.
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let node = try PureXML.parse(xml)
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// Or stream events without building a tree (drives chunked input too).
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var reader = PureXML.events(xml)
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while let event = try reader.next() {
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// handle .startElement / .characters / .endElement / ...
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}
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// DTD validation (opt-in: allowDoctype + optional resolver for trusted externals).
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let issues = try PureXML.validateAgainstInternalDTD(
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xmlWithDoctype,
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limits: .init(allowDoctype: true),
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)
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// XPath over a parsed tree.
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let titles = try PureXML.xpath("//title", over: node)
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.compactMap(\.element)
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```
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## Attribution
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PureXML is informed by the behavior of established XML parsers (`libxml2`,
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`expat`, Foundation's `XMLParser`) and by the W3C XML 1.0 specification, but it
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does not copy their implementation into `Sources/`. See
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[ATTRIBUTION.md](ATTRIBUTION.md).
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## Development Contract
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PureXML must stay dependency-free and portable. Before merging changes:
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- Swift tools version: 6.1
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- Package products: `PureXML`
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- SwiftPM dependencies: none
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- Hosted CI matrix: macOS, Linux, Windows, and WASM
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```sh
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bash scripts/check-all.sh
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```
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That command expands to:
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```sh
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bash scripts/check-style.sh
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bash scripts/check-namespacing.sh
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bash scripts/check-forbidden-patterns.sh
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swiftformat . --config .swiftformat --lint
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swiftlint --config .swiftlint.yml --strict
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swift build
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swift test
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```
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## License
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MIT.
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