fix: add npm retries for null versions or parseError

lib/datasource/npm.js

@@ -110,8 +110,15 @@ async function getDependency(name, retries = 5) {
       headers,
     })).body;
     if (!res.versions || !Object.keys(res.versions).length) {
+      // Registry returned a 200 OK but with no versions
+      if (retries <= 0) {
+        logger.info({ name }, 'No versions returned');
         return null;
       }
+      logger.info('No versions returned, retrying');
+      await delay(5000 / retries);
+      return getDependency(name, 0);
+    }
     // Determine repository URL
     let repositoryUrl;
     if (res.repository) {
@@ -142,19 +149,24 @@ async function getDependency(name, retries = 5) {
     return dep;
   } catch (err) {
     if (err.statusCode === 401) {
-      logger.info({ err, name }, `Dependency lookup unauthorized`);
+      logger.info({ err, name }, `Dependency lookup failure: unauthorized`);
       return null;
     }
     if (err.statusCode === 404) {
-      logger.info({ name }, `Dependency not found`);
+      logger.info({ name }, `Dependency lookup failure: not found`);
       logger.debug({ err });
       return null;
     }
     if (err.name === 'ParseError') {
       // Registry returned a 200 OK but got failed to parse it
+      if (retries <= 0) {
         logger.warn({ err }, 'npm registry failure: ParseError');
         throw new Error('registry-failure');
       }
+      logger.info({ err }, 'npm registry failure: ParseError, retrying');
+      await delay(5000 / retries);
+      return getDependency(name, retries - 1);
+    }
     if (err.statusCode === 429) {
       // This is bad if it ever happens, so we should error
       logger.error({ err }, 'npm registry failure: too many requests');

test/manager/npm/__snapshots__/registry.spec.js.snap

@@ -51,6 +51,8 @@ Object {
 }
 `;
 
+exports[`api/npm should retry when 408 or 5xx 1`] = `null`;
+
 exports[`api/npm should send an authorization header if provided 1`] = `
 Object {
   "dist-tags": Object {

test/manager/npm/registry.spec.js

@@ -35,7 +35,10 @@ describe('api/npm', () => {
     nock('https://registry.npmjs.org')
       .get('/foobar')
       .reply(200, missingVersions);
-    const res = await npm.getDependency('foobar');
+    nock('https://registry.npmjs.org')
+      .get('/foobar')
+      .reply(200, missingVersions);
+    const res = await npm.getDependency('foobar', 1);
     expect(res).toBe(null);
   });
   it('should fetch package info from npm', async () => {
@@ -70,12 +73,15 @@ describe('api/npm', () => {
     expect(res).toBeNull();
   });
   it('should throw error for unparseable', async () => {
+    nock('https://registry.npmjs.org')
+      .get('/foobar')
+      .reply(200, 'oops');
     nock('https://registry.npmjs.org')
       .get('/foobar')
       .reply(200, 'oops');
     let e;
     try {
-      await npm.getDependency('foobar');
+      await npm.getDependency('foobar', 1);
     } catch (err) {
       e = err;
     }
@@ -127,8 +133,8 @@ describe('api/npm', () => {
     nock('https://registry.npmjs.org')
       .get('/foobar')
       .reply(200);
-    const res = await npm.getDependency('foobar');
-    expect(res).toBe(null);
+    const res = await npm.getDependency('foobar', 2);
+    expect(res).toMatchSnapshot();
   });
   it('should throw error for others', async () => {
     nock('https://registry.npmjs.org')