fix(eagerloading): eagerloading with .first should behave same as .fetch

The `.first` took a shortcut and instead lazily eagerloaded the relationships, causing some runtime
constraints to fail. Now the behavior is same for both `.first` and `.fetch`

src/Lucid/EagerLoad/index.js

@@ -122,7 +122,7 @@ class EagerLoad {
     const relationsKeys = _.keys(this._relations)
 
     /**
-     * Since all rows will become to the same user, we just need
+     * Since all rows will belongs to the same user, we just need
      * any one instance for reading some properties of the
      * instance.
      */

src/Lucid/QueryBuilder/index.js

@@ -327,13 +327,7 @@ class QueryBuilder {
     }
 
     const modelInstance = this._mapRowToInstance(row)
-
-    /**
-     * Eagerload relations when defined on query
-     */
-    if (_.size(this._eagerLoads)) {
-      await modelInstance.loadMany(this._eagerLoads)
-    }
+    await this._eagerLoad([modelInstance])
 
     if (this.Model.$hooks) {
       await this.Model.$hooks.after.exec('find', modelInstance)

src/Lucid/Relations/BaseRelation.js

@@ -185,7 +185,11 @@ class BaseRelation {
    * @return {Object}
    */
   async eagerLoad (rows) {
-    this._eagerLoadFn(this.relatedQuery, this.foreignKey, this.mapValues(rows))
+    const mappedRows = this.mapValues(rows)
+    if (!mappedRows || !mappedRows.length) {
+      return this.group([])
+    }
+    this._eagerLoadFn(this.relatedQuery, this.foreignKey, mappedRows)
     const relatedInstances = await this.relatedQuery.fetch()
     return this.group(relatedInstances.rows)
   }

src/Lucid/Relations/BelongsToMany.js

@@ -566,7 +566,11 @@ class BelongsToMany extends BaseRelation {
    * @return {Object}
    */
   async eagerLoad (rows) {
-    this._eagerLoadFn(this.relatedQuery, this.foreignKey, this.mapValues(rows))
+    const mappedRows = this.mapValues(rows)
+    if (!mappedRows || !mappedRows.length) {
+      return this.group([])
+    }
+    this._eagerLoadFn(this.relatedQuery, this.foreignKey, mappedRows)
     const relatedInstances = await this.relatedQuery.fetch()
     return this.group(relatedInstances.rows)
   }
@@ -616,6 +620,7 @@ class BelongsToMany extends BaseRelation {
     const transformedValues = _.transform(relatedInstances, (result, relatedInstance) => {
       const foreignKeyValue = relatedInstance.$sideLoaded[`pivot_${this.foreignKey}`]
       const existingRelation = _.find(result, (row) => row.identity === foreignKeyValue)
+      this._addPivotValuesAsRelation(relatedInstance)
 
       /**
        * If there is an existing relation, add row to

src/Lucid/Relations/HasManyThrough.js

@@ -192,7 +192,12 @@ class HasManyThrough extends BaseRelation {
    * @return {Object}
    */
   async eagerLoad (rows) {
-    this._eagerLoadFn(this.relatedQuery, this.foreignKey, this.mapValues(rows), {
+    const mappedRows = this.mapValues(rows)
+    if (!mappedRows || !mappedRows.length) {
+      return this.group([])
+    }
+
+    this._eagerLoadFn(this.relatedQuery, this.foreignKey, mappedRows, {
       foreignTable: this.$foreignTable,
       foreignKey: this.foreignKey
     })

test/unit/lucid-has-many.spec.js

@@ -142,7 +142,7 @@ test.group('Relations | Has Many', (group) => {
     assert.instanceOf(user.getRelated('cars'), VanillaSerializer)
     assert.equal(user.getRelated('cars').size(), 2)
     assert.deepEqual(user.getRelated('cars').rows.map((car) => car.$parent), ['User', 'User'])
-    assert.equal(carQuery.sql, helpers.formatQuery('select * from "cars" where "user_id" = ?'))
+    assert.equal(carQuery.sql, helpers.formatQuery('select * from "cars" where "user_id" in (?)'))
     assert.deepEqual(carQuery.bindings, helpers.formatBindings([1]))
   })
 
@@ -318,7 +318,7 @@ test.group('Relations | Has Many', (group) => {
     assert.equal(user.getRelated('cars').size(), 2)
     assert.equal(user.getRelated('cars').first().getRelated('parts').size(), 2)
     assert.equal(user.getRelated('cars').last().getRelated('parts').size(), 2)
-    assert.equal(carQuery.sql, helpers.formatQuery('select * from "cars" where "user_id" = ?'))
+    assert.equal(carQuery.sql, helpers.formatQuery('select * from "cars" where "user_id" in (?)'))
     assert.equal(partQuery.sql, helpers.formatQuery('select * from "parts" where "car_id" in (?, ?)'))
   })
 
@@ -363,7 +363,7 @@ test.group('Relations | Has Many', (group) => {
     assert.equal(user.getRelated('cars').size(), 2)
     assert.equal(user.getRelated('cars').first().getRelated('parts').size(), 1)
     assert.equal(user.getRelated('cars').last().getRelated('parts').size(), 1)
-    assert.equal(carQuery.sql, helpers.formatQuery('select * from "cars" where "user_id" = ?'))
+    assert.equal(carQuery.sql, helpers.formatQuery('select * from "cars" where "user_id" in (?)'))
     assert.equal(partQuery.sql, helpers.formatQuery('select * from "parts" where "part_name" = ? and "car_id" in (?, ?)'))
   })
 
@@ -410,7 +410,7 @@ test.group('Relations | Has Many', (group) => {
 
     assert.equal(user.getRelated('cars').size(), 1)
     assert.equal(user.getRelated('cars').first().getRelated('parts').size(), 1)
-    assert.equal(carQuery.sql, helpers.formatQuery('select * from "cars" where "name" = ? and "user_id" = ?'))
+    assert.equal(carQuery.sql, helpers.formatQuery('select * from "cars" where "name" = ? and "user_id" in (?)'))
     assert.equal(partQuery.sql, helpers.formatQuery('select * from "parts" where "part_name" = ? and "car_id" in (?)'))
   })