Uninvoked empty snapshot fix

Updated evaluateLoadedSnapShots() in index.js to store newly generated
snapshots. Also, global.before() checks on the snapshots content initially to
prevent the creation of an empty snapshot file.

Author: mariya-gfx

.eslintrc

@@ -7,6 +7,7 @@
     "no-debugger": "warn"
   },
   "env": {
+    "mocha":true,
     "node": true
   }
 }

src/index.js

@@ -74,9 +74,13 @@ function registerCypressSnapshot () {
   }
 
   function evaluateLoadedSnapShots (js) {
-    la(is.string(js), 'expected JavaScript snapshot source', js)
-    console.log('read snapshots.js file')
-    const store = eval(js) || {}
+    let store = {}
+    if (js != null) {
+      la(is.string(js), 'expected JavaScript snapshot source', js)
+      console.log('read snapshots.js file')
+      store = eval(js) || {}
+      console.log('have %d snapshot(s)', countSnapshots(store))
+    }
     console.log('have %d snapshot(s)', countSnapshots(store))
     storeSnapshot = initStore(store)
   }
@@ -87,13 +91,6 @@ function registerCypressSnapshot () {
     if (config.useRelativeSnapshots) {
       readFile = cy
       .task('readFileMaybe', snapshotFileName)
-      .then(function (contents) {
-        if (!contents) {
-          return cy.writeFile(snapshotFileName, '', 'utf-8', { log: false })
-        }
-
-        return contents
-      })
     } else {
       readFile = cy
       .readFile(snapshotFileName, 'utf-8')
@@ -193,13 +190,16 @@ function registerCypressSnapshot () {
   global.after(function saveSnapshots () {
     if (storeSnapshot) {
       const snapshots = storeSnapshot()
-      console.log('%d snapshot(s) on finish', countSnapshots(snapshots))
+      const count = countSnapshots(snapshots)
+      console.log('%d snapshot(s) on finish', count)
       console.log(snapshots)
 
-      snapshots.__version = Cypress.version
-      const s = JSON.stringify(snapshots, null, 2)
-      const str = `module.exports = ${s}\n`
-      cy.writeFile(snapshotFileName, str, 'utf-8', { log: false })
+      if (count) {
+        snapshots.__version = Cypress.version
+        const s = JSON.stringify(snapshots, null, 2)
+        const str = `module.exports = ${s}\n`
+        cy.writeFile(snapshotFileName, str, 'utf-8', { log: false })
+      }
     }
   })