refactor(schema): store top-level primitive array paths in schema as 'arr.$', 'arr.$.$', etc.

Re: #6405

Author: vkarpov15

lib/schema.js

@@ -542,15 +542,17 @@ warnings.increment = '`increment` should not be used as a schema path name ' +
  */
 
 Schema.prototype.path = function(path, obj) {
+  // Convert to '.$' to check subpaths re: gh-6405
+  const cleanPath = path.replace(/\.\d+\./g, '.$.').replace(/\.\d+$/, '.$');
   if (obj === undefined) {
     if (this.paths.hasOwnProperty(path)) {
       return this.paths[path];
     }
-    if (this.subpaths.hasOwnProperty(path)) {
-      return this.subpaths[path];
+    if (this.subpaths.hasOwnProperty(cleanPath)) {
+      return this.subpaths[cleanPath];
     }
-    if (this.singleNestedPaths.hasOwnProperty(path)) {
-      return this.singleNestedPaths[path];
+    if (this.singleNestedPaths.hasOwnProperty(cleanPath)) {
+      return this.singleNestedPaths[cleanPath];
     }
 
     // Look for maps
@@ -628,6 +630,10 @@ Schema.prototype.path = function(path, obj) {
       this.singleNestedPaths[path + '.' + key] =
         schemaType.schema.singleNestedPaths[key];
     }
+    for (const key in schemaType.schema.subpaths) {
+      this.singleNestedPaths[path + '.' + key] =
+        schemaType.schema.subpaths[key];
+    }
 
     Object.defineProperty(schemaType.schema, 'base', {
       configurable: true,
@@ -656,6 +662,29 @@ Schema.prototype.path = function(path, obj) {
     });
   }
 
+  if (schemaType.$isMongooseArray && schemaType.caster instanceof SchemaType) {
+    let arrayPath = path;
+    let _schemaType = schemaType;
+
+    let toAdd = [];
+    while (_schemaType.$isMongooseArray) {
+      arrayPath = arrayPath + '.$';
+
+      // Skip arrays of document arrays
+      if (_schemaType.$isMongooseDocumentArray) {
+        toAdd = [];
+        break;
+      }
+      _schemaType = _schemaType.caster.clone();
+      _schemaType.path = arrayPath;
+      toAdd.push(_schemaType);
+    }
+
+    for (const _schemaType of toAdd) {
+      this.subpaths[_schemaType.path] = _schemaType;
+    }
+  }
+
   return this;
 };
 
@@ -939,6 +968,9 @@ Schema.prototype.indexedPaths = function indexedPaths() {
  */
 
 Schema.prototype.pathType = function(path) {
+  // Convert to '.$' to check subpaths re: gh-6405
+  const cleanPath = path.replace(/\.\d+\./g, '.$.').replace(/\.\d+$/, '.$');
+
   if (this.paths.hasOwnProperty(path)) {
     return 'real';
   }
@@ -948,10 +980,10 @@ Schema.prototype.pathType = function(path) {
   if (this.nested.hasOwnProperty(path)) {
     return 'nested';
   }
-  if (this.subpaths.hasOwnProperty(path)) {
+  if (this.subpaths.hasOwnProperty(cleanPath)) {
     return 'real';
   }
-  if (this.singleNestedPaths.hasOwnProperty(path)) {
+  if (this.singleNestedPaths.hasOwnProperty(cleanPath)) {
     return 'real';
   }
 
@@ -1080,7 +1112,7 @@ Schema.prototype.setupTimestamp = function(timestamps) {
 };
 
 /*!
- * ignore
+ * ignore. Deprecated re: #6405
  */
 
 function getPositionalPathType(self, path) {

test/schema.test.js

@@ -406,6 +406,13 @@ describe('schema', function() {
       assert.ok(mixed[4] instanceof Date);
       assert.ok(mixed[5] instanceof DocumentObjectId);
 
+      // gh-6405
+      assert.ok(Loki.path('dates.$') instanceof mongoose.Schema.Date);
+      assert.ok(Loki.path('numbers.$') instanceof mongoose.Schema.Number);
+      assert.ok(Loki.path('strings.$') instanceof mongoose.Schema.String);
+      assert.ok(Loki.path('buffers.$') instanceof mongoose.Schema.Buffer);
+      assert.ok(Loki.path('mixed.$') instanceof mongoose.Schema.Mixed);
+
       done();
     });