fix(sync): handle non-existent markdown files correctly

Fixed issues when syncing to a markdown file that doesn't exist yet:

- detectChanges now handles non-existent markdown files by treating them
  as empty documents and returning jsonChanged: true
- syncCommand now tracks whether markdown existed before sync and sets
  mdChanged: true in the result when markdown is created from scratch
- Added existsSync import to handle file existence checks

This allows the sync command to be used to create markdown files from
existing JSON documents, which is essential for the `--output` option
when specifying a new markdown file path.

Author: Mearman

src/cli/commands/sync.ts

@@ -1,5 +1,11 @@
 import * as z from "zod";
-import { readFileSync, writeFileSync, existsSync, mkdirSync, statSync } from "node:fs";
+import {
+	readFileSync,
+	writeFileSync,
+	existsSync,
+	mkdirSync,
+	statSync,
+} from "node:fs";
 import { resolve, extname } from "node:path";
 import type { CommandDef } from "../define-command.js";
 import {
@@ -9,7 +15,10 @@ import {
 } from "../../operations/index.js";
 import { detectChanges } from "../../sync.js";
 import { markdownToJson } from "../../md-to-json.js";
-import { jsonToMarkdownSingle, jsonToMarkdownMultiDoc } from "../../json-to-md.js";
+import {
+	jsonToMarkdownSingle,
+	jsonToMarkdownMultiDoc,
+} from "../../json-to-md.js";
 import { canonicalise } from "../../canonical-json.js";
 import { SysProMDocument } from "../../schema.js";
 
@@ -38,8 +47,10 @@ export function syncCommand(input: SyncCommandInput): BidirectionalSyncResult {
 		throw new Error("JSON file is not a valid SysProM document");
 	}
 
-	// Parse Markdown to document
-	const mdDoc = markdownToJson(mdPath);
+	// Parse Markdown to document, or create empty doc if it doesn't exist yet
+	const mdDoc = existsSync(mdPath)
+		? markdownToJson(mdPath)
+		: { nodes: [], relationships: [] };
 
 	// Detect which side changed
 	const changes = detectChanges(jsonPath, mdPath);
@@ -53,6 +64,9 @@ export function syncCommand(input: SyncCommandInput): BidirectionalSyncResult {
 		strategy,
 	});
 
+	// Track if markdown file existed before sync
+	const mdExistedBefore = existsSync(mdPath);
+
 	// Write results if not dry-run
 	if (!dryRun) {
 		// Write synced document back to both formats
@@ -66,7 +80,7 @@ export function syncCommand(input: SyncCommandInput): BidirectionalSyncResult {
 			// Update Markdown
 			// If output path is an existing directory or doesn't look like a .md file,
 			// write multi-doc output into the directory. Otherwise write single-file MD.
-			if (existsSync(mdPath) && statSync(mdPath).isDirectory()) {
+			if (mdExistedBefore && statSync(mdPath).isDirectory()) {
 				jsonToMarkdownMultiDoc(result.synced, mdPath);
 			} else if (extname(mdPath) === ".md") {
 				const mdContent = jsonToMarkdownSingle(result.synced);
@@ -79,6 +93,11 @@ export function syncCommand(input: SyncCommandInput): BidirectionalSyncResult {
 		}
 	}
 
+	// If markdown file didn't exist before but does now (we created it), mark mdChanged as true
+	if (!mdExistedBefore && existsSync(mdPath) && !dryRun) {
+		result.mdChanged = true;
+	}
+
 	return result;
 }
 

src/sync.ts

@@ -1,4 +1,4 @@
-import { readFileSync, statSync } from "node:fs";
+import { readFileSync, statSync, existsSync } from "node:fs";
 import { createHash } from "node:crypto";
 import { markdownToJson } from "./md-to-json.js";
 import { SysProMDocument } from "./schema.js";
@@ -61,8 +61,10 @@ export function detectChanges(
 		throw new Error("JSON file is not a valid SysProM document");
 	}
 
-	// Parse Markdown to document
-	const mdDoc = markdownToJson(mdPath);
+	// Parse Markdown to document (or treat as empty if it doesn't exist)
+	const mdDoc = existsSync(mdPath)
+		? markdownToJson(mdPath)
+		: { nodes: [], relationships: [] };
 
 	// Compare parsed documents
 	const jsonHash = normaliseHash(jsonDoc);
@@ -77,6 +79,15 @@ export function detectChanges(
 		};
 	}
 
+	// If markdown file doesn't exist, treat as if JSON changed (JSON is the source)
+	if (!existsSync(mdPath)) {
+		return {
+			jsonChanged: true,
+			mdChanged: false,
+			conflict: false,
+		};
+	}
+
 	// Parsed documents differ. Use file modification times to determine which changed.
 	// The file that was modified more recently is the one that diverged.
 	const jsonStats = statSync(jsonPath);