From 35ee14ab3f3d5c54f846d4a35cd2893d2cc06a6c Mon Sep 17 00:00:00 2001
From: Nitin Kumar <snitin315@gmail.com>
Date: Thu, 28 Oct 2021 17:41:03 -0700
Subject: [PATCH] fix: do not concatenate string literals

---
 lib/rules/prefer-template.js       |  6 +++---
 tests/lib/rules/prefer-template.js | 24 ++++++++++++++++++------
 2 files changed, 21 insertions(+), 9 deletions(-)

diff --git a/lib/rules/prefer-template.js b/lib/rules/prefer-template.js
index fbd9b5ca339..65826fd2bf2 100644
--- a/lib/rules/prefer-template.js
+++ b/lib/rules/prefer-template.js
@@ -202,11 +202,11 @@ module.exports = {
             }
 
             if (isConcatenation(currentNode) && !hasIdentifierReference(currentNode)) {
+                const nodeTexts = sourceCode.getText(currentNode).split("+");
 
-                // As there are no varibales used in this concatenation, we can sipmly calculate the concatenated string
-                const concatenatedText = sourceCode.getText(currentNode).split("+").map(e => e.trim().slice(1, -1)).join("");
+                nodeTexts[nodeTexts.length - 1] = ` \`${nodeTexts[nodeTexts.length - 1].trim().slice(1)}`;
 
-                return `\`${concatenatedText}\``;
+                return nodeTexts.join("+");
             }
 
             if (isConcatenation(currentNode) && hasStringLiteral(currentNode) && hasNonStringLiteral(currentNode)) {
diff --git a/tests/lib/rules/prefer-template.js b/tests/lib/rules/prefer-template.js
index ffb0cda86a9..a237183bc3d 100644
--- a/tests/lib/rules/prefer-template.js
+++ b/tests/lib/rules/prefer-template.js
@@ -227,25 +227,37 @@ ruleTester.run("prefer-template", rule, {
 
         // https://github.com/eslint/eslint/issues/15083
         {
-            code: "\"Hello \" + \"world \" + test",
-            output: "`Hello world ${  test}`",
+            code: "'a' + 'b' + foo",
+            output: "'a' + `b${  foo}`",
+            errors
+        },
+        {
+            code: "'a' + 'b' + foo + 'c' + 'd'",
+            output: "'a' + `b${  foo  }c` + `d`",
             errors
         },
         {
             code: "var foo = \"Hello \" + \"world \" + \"another \" + test",
-            output: "var foo = `Hello world another ${  test}`",
+            output: "var foo = \"Hello \" + \"world \" + `another ${  test}`",
+            errors
+        },
+        {
+            code: "'Hello ' + '\"world\" ' + test",
+            output: "'Hello ' + `\"world\" ${  test}`",
             errors
         },
         {
             code: "\"Hello \" + \"'world' \" + test",
-            output: "`Hello 'world' ${  test}`",
+            output: "\"Hello \" + `'world' ${  test}`",
             errors
         },
         {
             code: `"default-src 'self' https://*.google.com;"
             + "frame-ancestors 'none';"
-            + "report-to " + test + ";"`,
-            output: "`default-src 'self' https://*.google.com;frame-ancestors 'none';report-to ${  test  };`",
+            + "report-to " + foo + ";"`,
+            output: `"default-src 'self' https://*.google.com;"
+            + "frame-ancestors 'none';"
+            + \`report-to \${  foo  };\``,
             errors
         }
     ]