Add support for alias to Legacy Models

app/models/legacy-base.model.js

@@ -5,10 +5,10 @@
  * @module LegacyBaseModel
  */
 
-const { QueryBuilder } = require('objection')
 const path = require('path')
 
 const BaseModel = require('./base.model.js')
+const LegacyQueryBuilder = require('./legacy.query-builder.js')
 
 class LegacyBaseModel extends BaseModel {
   /**
@@ -36,10 +36,10 @@ class LegacyBaseModel extends BaseModel {
    *
    * See `schema()` for further details.
    *
-   * @returns {Object} a custom Objection `QueryBuilder`
+   * @returns {module:LegacyQueryBuilder} a custom Objection `QueryBuilder`
    */
   static get QueryBuilder () {
-    return SchemaQueryBuilder
+    return LegacyQueryBuilder
   }
 
   /**
@@ -223,11 +223,4 @@ class LegacyBaseModel extends BaseModel {
   }
 }
 
-class SchemaQueryBuilder extends QueryBuilder {
-  constructor (modelClass) {
-    super(modelClass)
-    this.withSchema(modelClass.schema)
-  }
-}
-
 module.exports = LegacyBaseModel

app/models/legacy.query-builder.js

@@ -0,0 +1,31 @@
+'use strict'
+
+/**
+ * Wrapper around Objection.js QueryBuilder to add schema and alias support to Legacy Models
+ * @module LegacyBaseModel
+ */
+
+const { QueryBuilder } = require('objection')
+
+class LegacyQueryBuilder extends QueryBuilder {
+  /**
+   * Wrapper around Objection.js QueryBuilder to add schema and alias support to Legacy Models
+   *
+   * @param {Object} modelClass The Objection legacy model to which this QueryBuilder will be applied
+   */
+  constructor (modelClass) {
+    super(modelClass)
+
+    // ALL legacy models must implement a `schema` property. So, we always call this
+    this.withSchema(modelClass.schema)
+
+    // Only alias those that need to alias the table name to avoid errors, for example, needing to alias
+    // `charge_elements` as 'charge_references' so we can link them to `charge_purposes` but call purposes
+    // `ChargeElements`.
+    if (modelClass.alias) {
+      this.alias(modelClass.alias)
+    }
+  }
+}
+
+module.exports = LegacyQueryBuilder

test/models/legacy.query-builder.test.js

@@ -0,0 +1,66 @@
+'use strict'
+
+'use strict'
+
+// Test framework dependencies
+const Lab = require('@hapi/lab')
+const Code = require('@hapi/code')
+
+const { describe, it } = exports.lab = Lab.script()
+const { expect } = Code
+
+// Test helpers
+const LegacyBaseModel = require('../../app/models/legacy-base.model.js')
+
+// Thing under test
+const LegacyQueryBuilder = require('../../app/models/legacy.query-builder.js')
+
+describe('Legacy Base model', () => {
+  describe('when given a model class with only a schema', () => {
+    class SchemaLegacyModel extends LegacyBaseModel {
+      static get tableName () {
+        return 'schemaTable'
+      }
+
+      static get schema () {
+        return 'water'
+      }
+
+      static get QueryBuilder () {
+        return LegacyQueryBuilder
+      }
+    }
+
+    it('adds the schema name to the table in the queries it generates', () => {
+      const result = SchemaLegacyModel.query().toKnexQuery().toQuery()
+
+      expect(result).to.endWith('from "water"."schema_table"')
+    })
+  })
+
+  describe('when given a model class with an alias', () => {
+    class AliasLegacyModel extends LegacyBaseModel {
+      static get tableName () {
+        return 'aliasTable'
+      }
+
+      static get schema () {
+        return 'water'
+      }
+
+      static get alias () {
+        return 'chargeReferences'
+      }
+
+      static get QueryBuilder () {
+        return LegacyQueryBuilder
+      }
+    }
+
+    it('aliases the table in the queries it generates', () => {
+      const result = AliasLegacyModel.query().toKnexQuery().toQuery()
+
+      expect(result).to.endWith('from "water"."alias_table" as "charge_references"')
+    })
+  })
+})