From d135aa8dca374856ebea4f096dba35b23cefe76b Mon Sep 17 00:00:00 2001
From: Josh Goldberg <me@joshuakgoldberg.com>
Date: Sun, 26 Apr 2020 17:45:27 -0400
Subject: [PATCH] Added basic @typescript-eslint/triple-slash-reference merger

---
 src/rules/mergers.ts                          |  2 ++
 .../tests/triple-slash-reference.test.ts      | 27 +++++++++++++++++++
 src/rules/mergers/triple-slash-reference.ts   |  5 ++++
 3 files changed, 34 insertions(+)
 create mode 100644 src/rules/mergers/tests/triple-slash-reference.test.ts
 create mode 100644 src/rules/mergers/triple-slash-reference.ts

diff --git a/src/rules/mergers.ts b/src/rules/mergers.ts
index a1bd04620..a08bfed5c 100644
--- a/src/rules/mergers.ts
+++ b/src/rules/mergers.ts
@@ -5,6 +5,7 @@ import { mergeNoCaller } from "./mergers/no-caller";
 import { mergeNoEval } from "./mergers/no-eval";
 import { mergeNoMemberDelimiterStyle } from "./mergers/member-delimiter-style";
 import { mergeNoUnnecessaryTypeAssertion } from "./mergers/no-unnecessary-type-assertion";
+import { mergeTripleSlashReference } from "./mergers/triple-slash-reference";
 
 export const mergers = new Map([
     ["@typescript-eslint/ban-types", mergeBanTypes],
@@ -12,6 +13,7 @@ export const mergers = new Map([
     ["@typescript-eslint/indent", mergeIndent],
     ["@typescript-eslint/member-delimiter-style", mergeNoMemberDelimiterStyle],
     ["@typescript-eslint/no-unnecessary-type-assertion", mergeNoUnnecessaryTypeAssertion],
+    ["@typescript-eslint/triple-slash-reference", mergeTripleSlashReference],
     ["no-caller", mergeNoCaller],
     ["no-eval", mergeNoEval],
 ]);
diff --git a/src/rules/mergers/tests/triple-slash-reference.test.ts b/src/rules/mergers/tests/triple-slash-reference.test.ts
new file mode 100644
index 000000000..07a58a354
--- /dev/null
+++ b/src/rules/mergers/tests/triple-slash-reference.test.ts
@@ -0,0 +1,27 @@
+import { mergeTripleSlashReference } from "../triple-slash-reference";
+
+const option = {
+    path: "always",
+    types: "prefer-import",
+    lib: "always",
+};
+
+describe(mergeTripleSlashReference, () => {
+    test("neither options existing", () => {
+        const result = mergeTripleSlashReference(undefined, undefined);
+
+        expect(result).toEqual([]);
+    });
+
+    test("only existing options", () => {
+        const result = mergeTripleSlashReference([option], undefined);
+
+        expect(result).toEqual([option]);
+    });
+
+    test("only new options", () => {
+        const result = mergeTripleSlashReference(undefined, [option]);
+
+        expect(result).toEqual([option]);
+    });
+});
diff --git a/src/rules/mergers/triple-slash-reference.ts b/src/rules/mergers/triple-slash-reference.ts
new file mode 100644
index 000000000..d89202e19
--- /dev/null
+++ b/src/rules/mergers/triple-slash-reference.ts
@@ -0,0 +1,5 @@
+import { RuleMerger } from "../merger";
+
+export const mergeTripleSlashReference: RuleMerger = (existingOptions, newOptions) => {
+    return [existingOptions?.[0] ?? newOptions?.[0]].filter(Boolean);
+};