prevent overriding pre-existing meta tags with shared attribute names

src/shared/getComponentOption.js

@@ -14,7 +14,7 @@ import deepmerge from 'deepmerge'
  * @return {Object} - final aggregated result
  */
 export default function getComponentOption (opts, result = {}) {
-  const { component, option, deep } = opts
+  const { component, option, deep, arrayMerge } = opts
   const { $options } = component
 
   // only collect option data if it exists
@@ -34,7 +34,7 @@ export default function getComponentOption (opts, result = {}) {
     }
 
     // merge with existing options
-    result = deepmerge(result, data)
+    result = deepmerge(result, data, { arrayMerge })
   }
 
   // collect & aggregate child options if deep = true
@@ -42,7 +42,7 @@ export default function getComponentOption (opts, result = {}) {
     const { $children } = component
     for (let i = 0, len = $children.length; i < len; i++) {
       const component = $children[i]
-      result = getComponentOption({ option, deep, component }, result)
+      result = getComponentOption({ option, deep, component, arrayMerge }, result)
     }
   }
 

src/shared/getMetaInfo.js

@@ -9,7 +9,41 @@ import getComponentOption from './getComponentOption'
  */
 export default function getMetaInfo (component) {
   // collect & aggregate all metaInfo $options
-  const info = getComponentOption({ component, option: 'metaInfo', deep: true })
+  const info = getComponentOption({
+    component,
+    option: 'metaInfo',
+    deep: true,
+    // In order to prevent certain tags from being overwritten,
+    // (like <meta name="description" ...> being overwritten by
+    // <meta name="keywords" ...>), we need to specify a different
+    // array merge strategy. This strategy exploits a trick
+    // with associative arrays in JS using O(1) lookup
+
+    /* eslint-disable no-labels */
+    arrayMerge (oldTags, newTags) {
+      const updatedTags = []
+      for (let oldTagIndex in oldTags) {
+        const oldTag = oldTags[oldTagIndex]
+        let sharedAttributes = false
+        ifTagsHaveEqualSharedAttributeValues: for (let newTagIndex in newTags) {
+          const newTag = newTags[newTagIndex]
+          for (let attribute in newTag) {
+            if (newTag.hasOwnProperty(attribute) && oldTag.hasOwnProperty(attribute)) {
+              if (oldTag[attribute] === newTag[attribute]) {
+                sharedAttributes = true
+                break ifTagsHaveEqualSharedAttributeValues
+              }
+            }
+          }
+        }
+        if (!sharedAttributes) {
+          updatedTags.push(oldTag)
+        }
+      }
+      return updatedTags.concat(newTags)
+    }
+    /* eslint-enable no-labels */
+  })
 
   // if any info options are a function, coerce them to the result of a call
   for (let key in info) {