made the serve_style.add and addStyle functions async and return promises

src/serve_style.js

@@ -198,9 +198,9 @@ export const serve_style = {
    * @param {object} programOpts - An object containing the program options
    * @param {Function} reportTiles Function for reporting tile sources.
    * @param {Function} reportFont Function for reporting font usage
-   * @returns {boolean} true if add is succesful
+   * @returns {Promise<boolean>} true if add is successful
    */
-  add: function (
+  add: async function (
     options,
     repo,
     params,
@@ -214,13 +214,20 @@ export const serve_style = {
 
     let styleFileData;
     try {
-      styleFileData = fs.readFileSync(styleFile); // TODO: could be made async if this function was
+      styleFileData = await fs.promises.readFile(styleFile);
     } catch (e) {
       console.log(`Error reading style file "${params.style}"`);
       return false;
     }
 
-    const styleJSON = JSON.parse(styleFileData);
+    let styleJSON;
+    try {
+      styleJSON = JSON.parse(styleFileData);
+    } catch (e) {
+      console.log(`Error parsing style JSON from "${params.style}"`);
+      return false;
+    }
+
     const validationErrors = validateStyleMin(styleJSON);
     if (validationErrors.length > 0) {
       console.log(`The file "${params.style}" is not a valid style file:`);

src/server.js

@@ -178,12 +178,12 @@ async function start(opts) {
    * @param {object} item - The style configuration object.
    * @param {boolean} allowMoreData - Whether to allow adding more data sources.
    * @param {boolean} reportFonts - Whether to report fonts.
-   * @returns {void}
+   * @returns {Promise<void>}
    */
-  function addStyle(id, item, allowMoreData, reportFonts) {
+  async function addStyle(id, item, allowMoreData, reportFonts) {
     let success = true;
     if (item.serve_data !== false) {
-      success = serve_style.add(
+      success = await serve_style.add(
         options,
         serving.styles,
         item,
@@ -271,6 +271,7 @@ async function start(opts) {
         item.serve_rendered = false;
       }
     }
+    return success;
   }
 
   for (const id of Object.keys(config.styles || {})) {
@@ -280,7 +281,7 @@ async function start(opts) {
       continue;
     }
   
-    addStyle(id, item, true, true);
+    startupPromises.push(addStyle(id, item, true, true));
   }
   startupPromises.push(
     serve_font(options, serving.fonts, opts).then((sub) => {