Revert assertion on content attribute and add test to prevent regression

packages/-ember-data/tests/unit/model-test.js

@@ -757,15 +757,8 @@ module('unit/model - Model', function (hooks) {
       @attr('string')
       name;
     }
-    class NativePostWithContent extends Model {
-      @attr('string')
-      content;
-      @attr('string')
-      name;
-    }
     const PROP_MAP = {
       _internalModel: NativePostWithInternalModel,
-      content: NativePostWithContent,
       currentState: NativePostWithCurrentState,
     };
 
@@ -805,7 +798,7 @@ module('unit/model - Model', function (hooks) {
       });
     }
 
-    ['_internalModel', 'content', 'currentState'].forEach(testReservedProperty);
+    ['_internalModel', 'currentState'].forEach(testReservedProperty);
 
     testInDebug('A subclass of Model throws an error when calling create() directly', async function (assert) {
       class NativePerson extends Model {}

packages/-ember-data/tests/unit/model/attr-test.js

@@ -158,4 +158,28 @@ module('unit/model/attr | attr syntax', function (hooks) {
 
     assert.strictEqual(userRecord.name, 'Chris', 'attr is correctly set: name');
   });
+
+  test('attr can be used to define an attribute with name "content"', async function (assert) {
+    class Blog extends Model {
+      @attr content;
+    }
+
+    owner.register('model:blog', Blog);
+
+    let BlogModel = store.modelFor('blog');
+    let attrs = BlogModel.attributes;
+    assert.true(attrs.has('content'), 'We have the attr: name');
+
+    let userRecord = store.push({
+      data: {
+        type: 'blog',
+        id: '1',
+        attributes: {
+          content: 'The best blog post',
+        },
+      },
+    });
+
+    assert.strictEqual(userRecord.content, 'The best blog post', 'attr is correctly set: content');
+  });
 });

packages/model/addon/-private/attr.js

@@ -130,7 +130,7 @@ function attr(type, options) {
   return computed({
     get(key) {
       if (DEBUG) {
-        if (['_internalModel', 'content', 'currentState'].indexOf(key) !== -1) {
+        if (['_internalModel', 'currentState'].indexOf(key) !== -1) {
           throw new Error(
             `'${key}' is a reserved property name on instances of classes extending Model. Please choose a different property name for your attr on ${this.constructor.toString()}`
           );
@@ -145,7 +145,7 @@ function attr(type, options) {
     },
     set(key, value) {
       if (DEBUG) {
-        if (['_internalModel', 'content', 'currentState'].indexOf(key) !== -1) {
+        if (['_internalModel', 'currentState'].indexOf(key) !== -1) {
           throw new Error(
             `'${key}' is a reserved property name on instances of classes extending Model. Please choose a different property name for your attr on ${this.constructor.toString()}`
           );

packages/model/addon/-private/belongs-to.js

@@ -143,7 +143,7 @@ function belongsTo(modelName, options) {
   return computed({
     get(key) {
       if (DEBUG) {
-        if (['_internalModel', 'content', 'recordData', 'currentState'].indexOf(key) !== -1) {
+        if (['_internalModel', 'recordData', 'currentState'].indexOf(key) !== -1) {
           throw new Error(
             `'${key}' is a reserved property name on instances of classes extending Model. Please choose a different property name for your belongsTo on ${this.constructor.toString()}`
           );
@@ -173,7 +173,7 @@ function belongsTo(modelName, options) {
     },
     set(key, value) {
       if (DEBUG) {
-        if (['_internalModel', 'content', 'recordData', 'currentState'].indexOf(key) !== -1) {
+        if (['_internalModel', 'recordData', 'currentState'].indexOf(key) !== -1) {
           throw new Error(
             `'${key}' is a reserved property name on instances of classes extending Model. Please choose a different property name for your belongsTo on ${this.constructor.toString()}`
           );

packages/model/addon/-private/has-many.js

@@ -183,7 +183,7 @@ function hasMany(type, options) {
   return computed({
     get(key) {
       if (DEBUG) {
-        if (['_internalModel', 'content', 'recordData', 'currentState'].indexOf(key) !== -1) {
+        if (['_internalModel', 'recordData', 'currentState'].indexOf(key) !== -1) {
           throw new Error(
             `'${key}' is a reserved property name on instances of classes extending Model. Please choose a different property name for your hasMany on ${this.constructor.toString()}`
           );
@@ -193,7 +193,7 @@ function hasMany(type, options) {
     },
     set(key, records) {
       if (DEBUG) {
-        if (['_internalModel', 'content', 'recordData', 'currentState'].indexOf(key) !== -1) {
+        if (['_internalModel', 'recordData', 'currentState'].indexOf(key) !== -1) {
           throw new Error(
             `'${key}' is a reserved property name on instances of classes extending Model. Please choose a different property name for your hasMany on ${this.constructor.toString()}`
           );

packages/model/addon/-private/model.js

@@ -2279,12 +2279,6 @@ if (DEBUG) {
         );
       }
 
-      if (!isDefaultEmptyDescriptor(this, 'content') || this.content !== undefined) {
-        throw new Error(
-          `'content' is a reserved property name on instances of classes extending Model. Please choose a different property name for ${this.constructor.toString()}`
-        );
-      }
-
       let ourDescriptor = lookupDescriptor(Model.prototype, 'currentState');
       let theirDescriptor = lookupDescriptor(this, 'currentState');
       let realState = this.___recordState || this._internalModel.currentState;