Error handling proposal

Author: tshemsedinov

application/api/.eslintrc.json

@@ -10,6 +10,7 @@
     "db": "readonly",
     "bus": "readonly",
     "domain": "readonly",
-    "metarhia": "readonly"
+    "metarhia": "readonly",
+    "DomainError": "readonly"
   }
 }

application/api/console.1/console.d.ts

@@ -0,0 +1,5 @@
+type Code = 'ENOTFOUND' | 'EPARSE';
+
+class DomainError {
+  constructor(code: Code);
+}

application/api/console.1/content.js

@@ -1,6 +1,8 @@
 ({
   access: 'public',
   async method({ name }) {
+    // it doesn't work in IDE, but works in runtime:
+    // new DomainError('EPARSE');
     const filePath = `/content/${name}.md`;
     const buffer = application.resources.get(filePath);
     if (!buffer) return new Error('Content is not found');

application/api/example.1/add.js

@@ -5,9 +5,32 @@
   },
 
   method: async ({ a, b }) => {
+    if (typeof a !== 'number') return new DomainError('EARGA');
+    if (typeof b !== 'number') {
+      return new api.example.example.CustomError('EARGB');
+    }
+    if (Number.isNaN(a)) throw Error('Not a number: a');
+    if (Number.isNaN(b)) throw Error('Not a number: b');
     const result = a + b;
     return result;
   },
 
   returns: 'number',
+
+  errors: {
+    EARGA: 'Invalid argument: a',
+    EARGB: 'Invalid argument: b',
+  },
+
+  onError(error) {
+    if (error.code in this.errors) {
+      console.log(`Domain error detected: ${error.code}`);
+    }
+    return error;
+  },
+
+  onException(error) {
+    console.log(`Exception throws: ${error.message}`);
+    return error;
+  },
 });

application/api/example.1/example.d.ts

@@ -0,0 +1,15 @@
+type Code = 'EARGA' | 'EARGB';
+
+class DomainError {
+  constructor(code: Code);
+}
+
+namespace api.example.example {
+  class CustomError extends DomainError {
+    toJSON() {
+      const { name, code, message, stack } = this;
+      return { name, code, message, stack };
+    }
+  }
+}
+

application/api/example.1/example.js

@@ -0,0 +1,8 @@
+({
+  CustomError: class CustomError extends DomainError {
+    toJSON() {
+      const { name, code, message, stack } = this;
+      return { name, code, message, stack };
+    }
+  },
+});