Fix using concat() on single Doc (#9994)

Co-authored-by: Sosuke Suzuki <aosukeke@gmail.com>

scripts/tools/eslint-plugin-prettier-internal-rules/index.js

@@ -7,6 +7,7 @@ module.exports = {
     "jsx-identifier-case": require("./jsx-identifier-case"),
     "no-doc-builder-concat": require("./no-doc-builder-concat"),
     "no-node-comments": require("./no-node-comments"),
+    "no-single-doc-concat": require("./no-single-doc-concat"),
     "prefer-fast-path-each": require("./prefer-fast-path-each"),
     "prefer-is-non-empty-array": require("./prefer-is-non-empty-array"),
     "require-json-extensions": require("./require-json-extensions"),

scripts/tools/eslint-plugin-prettier-internal-rules/no-single-doc-concat.js

@@ -0,0 +1,44 @@
+"use strict";
+
+// TODO: Remove this rule when deprecated `concat` is not using in codebase, #9993.
+
+const selector = [
+  "CallExpression",
+  '[callee.type="Identifier"]',
+  '[callee.name="concat"]',
+  "[arguments.length=1]",
+  '[arguments.0.type="ArrayExpression"]',
+  "[arguments.0.elements.length=1]",
+].join("");
+
+const messageId = "no-single-doc-concat";
+
+module.exports = {
+  meta: {
+    type: "suggestion",
+    docs: {
+      url:
+        "https://github.com/prettier/prettier/blob/master/scripts/eslint-plugin-prettier-internal-rules/no-single-doc-concat.js",
+    },
+    messages: {
+      [messageId]: "Do not use `concat()` to concat single `Doc`.",
+    },
+    fixable: "code",
+  },
+  create(context) {
+    const sourceCode = context.getSourceCode();
+    return {
+      [selector](node) {
+        context.report({
+          node,
+          messageId,
+          fix: (fixer) =>
+            fixer.replaceText(
+              node,
+              sourceCode.getText(node.arguments[0].elements[0])
+            ),
+        });
+      },
+    };
+  },
+};

scripts/tools/eslint-plugin-prettier-internal-rules/test.js

@@ -144,6 +144,17 @@ test("no-node-comments", {
   ],
 });
 
+test("no-single-doc-concat", {
+  valid: [],
+  invalid: [
+    {
+      code: 'concat([path.call(print, "params")])',
+      output: 'path.call(print, "params")',
+      errors: 1,
+    },
+  ],
+});
+
 test("prefer-fast-path-each", {
   valid: ["const foo = path.map()"],
   invalid: [