fix: report relevant error on invalid jsons (#80)

Author: erezrokah

src/config.js

@@ -38,12 +38,20 @@ const getConfiguration = ({ constants, inputs } = {}) => {
     (inputs && inputs.thresholds) || process.env.THRESHOLDS || {};
 
   if (typeof thresholds === 'string') {
-    thresholds = JSON.parse(thresholds);
+    try {
+      thresholds = JSON.parse(thresholds);
+    } catch (e) {
+      throw new Error(`Invalid JSON for 'thresholds' input: ${e.message}`);
+    }
   }
 
   let audits = (inputs && inputs.audits) || process.env.AUDITS;
   if (typeof audits === 'string') {
-    audits = JSON.parse(audits);
+    try {
+      audits = JSON.parse(audits);
+    } catch (e) {
+      throw new Error(`Invalid JSON for 'audits' input: ${e.message}`);
+    }
   }
 
   if (!Array.isArray(audits)) {

src/config.test.js

@@ -137,4 +137,32 @@ describe('config', () => {
       audits: [{ path: 'PUBLISH_DIR/a/b', thresholds: {} }],
     });
   });
+
+  it('should throw error on invalid thresholds json input', () => {
+    const constants = { THRESHOLDS: 'PUBLISH_DIR' };
+    const inputs = {
+      thresholds: 'invalid_json',
+      audits: [{}],
+    };
+
+    expect(() => getConfiguration({ constants, inputs })).toThrow(
+      new Error(
+        `Invalid JSON for 'thresholds' input: Unexpected token i in JSON at position 0`,
+      ),
+    );
+  });
+
+  it('should throw error on invalid audits json input', () => {
+    const constants = { THRESHOLDS: 'PUBLISH_DIR' };
+    const inputs = {
+      thresholds: { performance: 1 },
+      audits: 'invalid_json',
+    };
+
+    expect(() => getConfiguration({ constants, inputs })).toThrow(
+      new Error(
+        `Invalid JSON for 'audits' input: Unexpected token i in JSON at position 0`,
+      ),
+    );
+  });
 });