From 33d050f361286fde5f1d74551c22829c7e6a349a Mon Sep 17 00:00:00 2001
From: Marcelo Boveto Shima <marceloshima@gmail.com>
Date: Sat, 20 Feb 2021 10:26:12 -0300
Subject: [PATCH] Implement getFeatures for singleton support.

---
 lib/index.js | 34 ++++++++++++++++++++++++++++++++++
 test/base.js | 17 +++++++++++++++++
 2 files changed, 51 insertions(+)

diff --git a/lib/index.js b/lib/index.js
index 1ee1df6b..c866ede4 100644
--- a/lib/index.js
+++ b/lib/index.js
@@ -111,6 +111,9 @@ class Generator extends Base {
    * @param {string[]} args           - Provide arguments at initialization
    * @param {Object} options          - Provide options at initialization
    * @param {Priority[]} [options.customPriorities] - Custom priorities
+   * @param {boolean|string} [options.unique] - Generates a uniqueBy id for the environment
+   *                                    Accepts 'namespace' or 'true' for one instance by namespace
+                                        Accepts 'argument' for one instance by namespace and 1 argument
    *
    * @property {Object}   env         - the current Environment being run
    * @property {String}   resolved    - the path to the current generator
@@ -266,6 +269,37 @@ class Generator extends Base {
     }
   }
 
+  /**
+   * Specifications for Environment features.
+   *
+   * @return {Object}
+   */
+  getFeatures() {
+    if (this.options.unique) {
+      const {namespace} = this.options;
+      let uniqueBy;
+      if (this.options.unique === true || this.options.unique === 'namespace') {
+        uniqueBy = namespace;
+      } else if (
+        this.options.unique === 'argument' &&
+        this._args.length === 1
+      ) {
+        const namespaceId = this.env
+          .requireNamespace(namespace)
+          .with({instanceId: this._args[0]});
+        uniqueBy = namespaceId.id;
+      } else {
+        throw new Error(
+          `Error generating a uniqueBy value. Uniqueness ${this.options.unique} is not supported`
+        );
+      }
+
+      return {uniqueBy};
+    }
+
+    return {};
+  }
+
   /**
    * Register priorities for this generator
    *
diff --git a/test/base.js b/test/base.js
index 83dd6ebf..8272b81f 100644
--- a/test/base.js
+++ b/test/base.js
@@ -1784,4 +1784,21 @@ describe('Base', () => {
       });
     });
   });
+
+  describe.only('#getFeatures', () => {
+    it('should return namespace as uniqueBy when unique is true', function () {
+      const gen = new Base([], {unique: true, namespace: 'foo', env: this.env});
+      assert.equal(gen.getFeatures().uniqueBy, 'foo');
+    });
+
+    it("should return namespace as uniqueBy when unique is 'namespace'", function () {
+      const gen = new Base([], {unique: 'namespace', namespace: 'foo', env: this.env});
+      assert.equal(gen.getFeatures().uniqueBy, 'foo');
+    });
+
+    it("should return namespace with first argument as uniqueBy when unique is 'namespace'", function () {
+      const gen = new Base(['bar'], {unique: 'argument', namespace: 'foo', env: this.env});
+      assert.equal(gen.getFeatures().uniqueBy, 'foo#bar');
+    });
+  });
 });