analyse which env vars should not be overwritten fastify#558

lib/watch/index.js

@@ -37,25 +37,34 @@ const watch = function (args, ignoreWatch, verboseWatch) {
   })
 
   let readyEmitted = false
+  const envVarsToProtect = [];
 
   const run = (event) => {
     const childEvent = { childEvent: event }
 
     // in order to not override existing env vars, we have to load and parse
     // dotenv without modifying process.env
-    let dotenvParsed = {}
-    const dotenvPath = path.resolve(process.cwd(), '.env')
+    let dotenvParsed = {};
+    const dotenvPath = path.resolve(process.cwd(), '.env');
     if (existsSync(dotenvPath)) {
-      dotenvParsed = require('dotenv').parse(readFileSync(dotenvPath, { encoding: 'utf-8' }))
-      Object.keys(dotenvParsed).forEach(function (key) {
-        if (Object.prototype.hasOwnProperty.call(process.env, key)) {
-          // we do not want to overrideexisting env-vars
-          delete dotenvParsed[key]
-        }
-      })
+      dotenvParsed = require('dotenv').parse(readFileSync(dotenvPath, { encoding: 'utf-8' }));
+      if (event == 'start') {
+        // analyse which env-vars should not be overwritten
+        Object.keys(dotenvParsed).forEach(function (key) {
+          if (Object.prototype.hasOwnProperty.call(process.env, key)) {
+            // if a env var already exists with a different value
+            // than in parsed dotenv, it has to be protected
+            if (process.env[key] != dotenvParsed[key]) {
+              envVarsToProtect.push(key);
+            }
+          }
+        });
+      }
+      for (const envVarToProtect of envVarsToProtect) {
+        delete dotenvParsed[envVarToProtect];
+      }
     }
-    // const env = Object.assign({}, process.env, childEvent, dotenvParsed)
-    const env = Object.assign({}, dotenvParsed, process.env, childEvent)
+    const env = Object.assign({}, process.env, dotenvParsed, childEvent);
 
     const _child = cp.fork(forkPath, args, {
       env,