Add file parser

Author: mayank1513

lib/package.json

@@ -39,12 +39,16 @@
     "@types/picomatch": "^4.0.2",
     "@vitest/coverage-v8": "^3.2.4",
     "esbuild-plugin-rdi": "^0.0.0",
+    "fast-xml-parser": "^5.2.5",
+    "json5": "^2.2.3",
     "micromatch": "^4.0.8",
     "picomatch": "^4.0.3",
+    "toml": "^3.0.0",
     "tsup": "^8.5.0",
     "typescript": "^5.9.2",
     "vite-tsconfig-paths": "^5.1.4",
-    "vitest": "^3.2.4"
+    "vitest": "^3.2.4",
+    "yaml": "^2.8.1"
   },
   "funding": [
     {
@@ -70,5 +74,33 @@
     "tooling",
     "react18-tools",
     "mayank1513"
-  ]
+  ],
+  "peerDependencies": {
+    "fast-xml-parser": "^5.2.5",
+    "json5": "^2.2.3",
+    "micromatch": "^4.0.8",
+    "picomatch": "^4.0.3",
+    "toml": "^3.0.0",
+    "yaml": "^2.8.1"
+  },
+  "peerDependenciesMeta": {
+    "fast-xml-parser": {
+      "optional": true
+    },
+    "json5": {
+      "optional": true
+    },
+    "micromatch": {
+      "optional": true
+    },
+    "picomatch": {
+      "optional": true
+    },
+    "toml": {
+      "optional": true
+    },
+    "yaml": {
+      "optional": true
+    }
+  }
 }

lib/src/file-parser.ts

@@ -0,0 +1,212 @@
+/**
+ * Represents a parsed conflict from a file with `ours` and `theirs` versions.
+ *
+ * @template T - The type of the parsed content.
+ */
+export interface ParsedConflict<T = unknown> {
+  /** Parsed content from the "ours" side of the conflict. */
+  ours: T;
+  /** Parsed content from the "theirs" side of the conflict. */
+  theirs: T;
+  /** Format used to parse the content (`json`, `yaml`, `toml`, `xml`, or `custom`). */
+  format: string;
+}
+
+/** A parser function that takes a raw string and returns parsed content. */
+export type Parser = (input: string) => unknown;
+
+/** Built-in parser identifiers or a custom parser function. */
+export type SupportedParsers = "json" | "json5" | "yaml" | "toml" | "xml" | Parser;
+
+/**
+ * Options for parsing conflicted content.
+ */
+export interface ParseConflictOptions {
+  /**
+   * Parsers to attempt, in order:
+   * - A single parser (`"json"`, `"yaml"`, custom function, etc.).
+   * - An array of parsers (e.g. `["yaml", "json5"]`).
+   *
+   * Defaults to `"json"`.
+   */
+  parsers?: "auto" | SupportedParsers | SupportedParsers[];
+
+  /**
+   * Optional filename hint to prioritize parser choice.
+   * Example:
+   * - `config.yaml` → try `yaml` first.
+   * - `data.toml` → try `toml` first.
+   *
+   * If extension is unknown, falls back to `parsers` or `"json"`.
+   */
+  filename?: string;
+}
+
+/**
+ * Parses a conflicted file's content into separate `ours` and `theirs` objects.
+ *
+ * - Preserves non-conflicted lines in both versions.
+ * - Supports JSON, JSON5, YAML, TOML, and XML.
+ * - Lazy-loads optional peer dependencies (`json5`, `yaml`, `toml`, `fast-xml-parser`).
+ * - Parser order is determined by:
+ *   1. `filename` extension hint (if provided).
+ *   2. Explicit `parsers` option.
+ *   3. Default `"json"`.
+ *
+ * @template T - Expected type of parsed content.
+ * @param content - Raw file content containing conflict markers.
+ * @param options - Parsing options (parsers + filename hint).
+ * @returns Parsed conflict with both sides and detected format.
+ * @throws If parsing fails or conflict markers are invalid.
+ */
+export const parseConflictContent = async <T = unknown>(
+  content: string,
+  options: ParseConflictOptions = {},
+): Promise<ParsedConflict<T>> => {
+  const lines = content.split("\n");
+  const oursLines: string[] = [];
+  const theirsLines: string[] = [];
+
+  enum State {
+    Normal,
+    InOurs,
+    InTheirs,
+  }
+  let state = State.Normal;
+
+  for (const line of lines) {
+    if (line.startsWith("<<<<<<<")) {
+      state = State.InOurs;
+      continue;
+    } else if (line.startsWith("=======")) {
+      if (state === State.InOurs) state = State.InTheirs;
+      continue;
+    } else if (line.startsWith(">>>>>>>")) {
+      if (state === State.InTheirs) state = State.Normal;
+      continue;
+    }
+
+    switch (state) {
+      case State.Normal:
+        oursLines.push(line);
+        theirsLines.push(line);
+        break;
+      case State.InOurs:
+        oursLines.push(line);
+        break;
+      case State.InTheirs:
+        theirsLines.push(line);
+        break;
+    }
+  }
+
+  const oursRaw = oursLines.join("\n");
+  const theirsRaw = theirsLines.join("\n");
+
+  if (!oursRaw || !theirsRaw) {
+    throw new Error("Conflict parsing resulted in empty content.");
+  }
+
+  // normalize parser list
+  const parsers = normalizeParsers(options);
+
+  const [oursParsed, format] = await runParser(oursRaw, parsers);
+  const [theirsParsed] = await runParser(theirsRaw, [format]);
+
+  return {
+    ours: oursParsed as T,
+    theirs: theirsParsed as T,
+    format: typeof format === "function" ? "custom" : format,
+  };
+};
+
+/** Normalize parsers based on filename + options. */
+const normalizeParsers = (options: ParseConflictOptions): SupportedParsers[] => {
+  if (options.parsers) {
+    return Array.isArray(options.parsers)
+      ? options.parsers
+      : options.parsers === "auto"
+        ? ["json", "json5", "yaml", "toml", "xml"]
+        : [options.parsers];
+  }
+
+  if (options.filename) {
+    const ext = options.filename.split(".").pop()?.toLowerCase();
+    switch (ext) {
+      case "json":
+        return ["json"];
+      case "json5":
+        return ["json5"];
+      case "yaml":
+      case "yml":
+        return ["yaml"];
+      case "toml":
+        return ["toml"];
+      case "xml":
+        return ["xml"];
+    }
+  }
+
+  return ["json"]; // default
+};
+
+/** Internal helper to try parsers in order. */
+const runParser = async (
+  raw: string,
+  parsers: SupportedParsers[],
+): Promise<[unknown, SupportedParsers]> => {
+  for (const parser of parsers) {
+    try {
+      if (typeof parser === "function") return [parser(raw), parser];
+      return [await parseFormat(parser, raw), parser];
+    } catch (err) {
+      console.debug(`Parser ${typeof parser === "function" ? "custom" : parser} failed:`, err);
+    }
+  }
+  throw new Error(
+    `Failed to parse content. Tried parsers: ${parsers.map(p => (typeof p === "string" ? p : "custom")).join(", ")}`,
+  );
+};
+
+/** Internal parser dispatcher for supported formats. */
+const parseFormat = async (
+  parser: "json" | "json5" | "yaml" | "toml" | "xml",
+  raw: string,
+): Promise<unknown> => {
+  switch (parser) {
+    case "json":
+      return JSON.parse(raw);
+    case "json5": {
+      try {
+        const { parse } = await import("json5");
+        return parse(raw);
+      } catch {
+        throw new Error("json5 parser not installed. Please install as peer dependency.");
+      }
+    }
+    case "yaml": {
+      try {
+        const { parse } = await import("yaml");
+        return parse(raw);
+      } catch {
+        throw new Error("yaml parser not installed. Please install as peer dependency.");
+      }
+    }
+    case "toml": {
+      try {
+        const { parse } = await import("toml");
+        return parse(raw);
+      } catch {
+        throw new Error("toml parser not installed. Please install as peer dependency.");
+      }
+    }
+    case "xml": {
+      try {
+        const { XMLParser } = await import("fast-xml-parser");
+        return new XMLParser().parse(raw);
+      } catch {
+        throw new Error("fast-xml-parser not installed. Please install as peer dependency.");
+      }
+    }
+  }
+};