Fix up lint

.eslintrc.json

@@ -0,0 +1,22 @@
+{
+  "extends": [
+    "airbnb-base",
+    "prettier"
+  ],
+  "env": {
+    "jest": true,
+    "node": true
+  },
+  "rules": {
+    "no-unused-vars": [
+      "error",
+      {
+        "argsIgnorePattern": "^_",
+        "varsIgnorePattern": "^_"
+      }
+    ],
+    "prefer-destructuring": "off",
+    "prefer-object-spread": "off",
+    "prefer-spread": "off"
+  }
+}

.gitignore

@@ -1 +1,2 @@
-node_modules/
+/.eslintcache
+/node_modules/

src/parse.js

@@ -0,0 +1,38 @@
+const parser = require("fast-xml-parser");
+
+const translate = (node, name) => {
+  if (typeof node !== "object") {
+    return { type: "leaf", name, attrs: {}, value: node.toString() };
+  }
+
+  const attrs = {};
+  const value = [];
+
+  Object.keys(node).forEach(key => {
+    if (key.startsWith("@_")) {
+      attrs[key.slice(2)] = node[key];
+    } else if (key !== "#text") {
+      value.push(translate(node[key], key));
+    }
+  });
+
+  if (Object.prototype.hasOwnProperty.call(node, "#text")) {
+    return { type: "leaf", name, attrs, value: node["#text"] };
+  }
+
+  return { type: "node", name, attrs, value };
+};
+
+const parse = (text, _parsers, _opts) => Object.assign(
+  {},
+  translate(parser.parse(text, {
+    allowBooleanAttributes: true,
+    attributeNamePrefix : "@_",
+    ignoreAttributes: false,
+    parseAttributeValue: true,
+    textNodeName: "#text"
+  })),
+  { type: "root" }
+);
+
+module.exports = parse;

src/plugin.js

@@ -0,0 +1,46 @@
+const parse = require("./parse");
+const print = require("./print");
+
+// These functions are necessary or the print with cursor function breaks.
+// Eventually we should fill them in with the correct metadata, but the parser
+// doesn't provide it at the moment.
+const locStart = _node => 0;
+const locEnd = _node => 0;
+
+const plugin = {
+  languages: [
+    {
+      name: "XML",
+      parsers: ["xml"],
+      extensions: [".xml"]
+    }
+  ],
+  parsers: {
+    xml: {
+      parse,
+      astFormat: "xml",
+      locStart,
+      locEnd
+    }
+  },
+  printers: {
+    xml: {
+      print
+    }
+  },
+  options: {
+    xmlSelfClosingTags: {
+      since: "1.19.1",
+      category: "XML",
+      type: "boolean",
+      default: true,
+      description: "Whether or not to allow self closing XML tags."
+    }
+  },
+  defaultOptions: {
+    printWidth: 80,
+    tabWidth: 2
+  }
+};
+
+module.exports = plugin;

src/print.js

@@ -0,0 +1,84 @@
+const { concat, group, hardline, indent, join, line, softline } = require("prettier").doc.builders;
+
+const getFirstNonBlankLine = originalText => originalText.split("\n").find(
+  text => text.trim().length !== 0
+);
+
+const printAttrs = attrs => {
+  if (Object.keys(attrs).length === 0) {
+    return "";
+  }
+
+  const parts = [line];
+
+  Object.keys(attrs).forEach((key, index) => {
+    if (index !== 0) {
+      parts.push(line);
+    }
+    parts.push(key, "=", '"', attrs[key], '"');
+  });
+
+  return group(concat([indent(concat(parts)), softline]));
+};
+
+const genericPrint = (path, opts, print) => {
+  const { type, name, attrs, value } = path.getValue();
+
+  switch (type) {
+    case "leaf": {
+      const parts = [
+        "<",
+        name,
+        printAttrs(attrs)
+      ];
+
+      if (!value && opts.xmlSelfClosingTags) {
+        return group(concat(parts.concat(" />")));
+      }
+
+      return group(concat(parts.concat(
+        ">",
+        indent(concat([
+          softline,
+          value
+        ])),
+        softline,
+        "</",
+        name,
+        ">"
+      )));
+    }
+    case "node":
+      return group(concat([
+        "<",
+        name,
+        printAttrs(attrs),
+        ">",
+        indent(concat([
+          hardline,
+          join(hardline, path.map(print, "value"))
+        ])),
+        hardline,
+        "</",
+        name,
+        ">"
+      ]));
+    case "root": {
+      const parts = [
+        join(hardline, path.map(print, "value")),
+        hardline
+      ];
+
+      const firstNonBlankLine = getFirstNonBlankLine(opts.originalText);
+      if (firstNonBlankLine && firstNonBlankLine.startsWith("<?xml")) {
+        parts.unshift(firstNonBlankLine, hardline);
+      }
+
+      return concat(parts);
+    }
+    default:
+      throw new Error(`Unsupported node encountered: ${type}`);
+  }
+};
+
+module.exports = genericPrint;