From 9f6584c955c03bea431dbeb2378417434ca7b29c Mon Sep 17 00:00:00 2001
From: Teddy Katz <teddy.katz@gmail.com>
Date: Sun, 4 Mar 2018 18:31:01 -0500
Subject: [PATCH] Breaking: require rules to provide report messages (fixes
 #10011)

This updates ESLint core to throw an error when a rule reports a problem without providing a report message. It is unlikely that many users were relying on the previous behavior, because a reported problem without a message would crash several formatters, including the default formatter. However, it is possible that someone was relying on this with the `json` formatter.
---
 lib/report-translator.js       | 19 ++++++++-----------
 tests/lib/linter.js            | 14 ++++++++++++++
 tests/lib/report-translator.js |  9 +++++++++
 3 files changed, 31 insertions(+), 11 deletions(-)

diff --git a/lib/report-translator.js b/lib/report-translator.js
index 7893a1f7ad2..703060e74ac 100644
--- a/lib/report-translator.js
+++ b/lib/report-translator.js
@@ -113,15 +113,6 @@ function normalizeReportLoc(descriptor) {
     return descriptor.node.loc;
 }
 
-/**
- * Interpolates data placeholders in report messages
- * @param {MessageDescriptor} descriptor The report message descriptor.
- * @returns {string} The interpolated message for the descriptor
- */
-function normalizeMessagePlaceholders(descriptor) {
-    return interpolate(descriptor.message, descriptor.data);
-}
-
 /**
  * Compares items in a fixes array by range.
  * @param {Fix} a The first message.
@@ -255,6 +246,8 @@ module.exports = function createReportTranslator(metadata) {
 
         assertValidNodeInfo(descriptor);
 
+        let computedMessage;
+
         if (descriptor.messageId) {
             if (!metadata.messageIds) {
                 throw new TypeError("context.report() called with a messageId, but no messages were present in the rule metadata.");
@@ -268,7 +261,11 @@ module.exports = function createReportTranslator(metadata) {
             if (!messages || !Object.prototype.hasOwnProperty.call(messages, id)) {
                 throw new TypeError(`context.report() called with a messageId of '${id}' which is not present in the 'messages' config: ${JSON.stringify(messages, null, 2)}`);
             }
-            descriptor.message = messages[id];
+            computedMessage = messages[id];
+        } else if (descriptor.message) {
+            computedMessage = descriptor.message;
+        } else {
+            throw new TypeError("Missing `message` property in report() call; add a message that describes the linting problem.");
         }
 
 
@@ -276,7 +273,7 @@ module.exports = function createReportTranslator(metadata) {
             ruleId: metadata.ruleId,
             severity: metadata.severity,
             node: descriptor.node,
-            message: normalizeMessagePlaceholders(descriptor),
+            message: interpolate(computedMessage, descriptor.data),
             messageId: descriptor.messageId,
             loc: normalizeReportLoc(descriptor),
             fix: normalizeFixes(descriptor, metadata.sourceCode),
diff --git a/tests/lib/linter.js b/tests/lib/linter.js
index 7c3ac678afb..2244ade3573 100644
--- a/tests/lib/linter.js
+++ b/tests/lib/linter.js
@@ -870,6 +870,20 @@ describe("Linter", () => {
             sinon.assert.calledTwice(spyLiteral);
             sinon.assert.calledOnce(spyBinaryExpression);
         });
+
+        it("should throw an error if a rule reports a problem without a message", () => {
+            linter.defineRule("invalid-report", context => ({
+                Program(node) {
+                    context.report({ node });
+                }
+            }));
+
+            assert.throws(
+                () => linter.verify("foo", { rules: { "invalid-report": "error" } }),
+                TypeError,
+                "Missing `message` property in report() call; add a message that describes the linting problem."
+            );
+        });
     });
 
     describe("when config has shared settings for rules", () => {
diff --git a/tests/lib/report-translator.js b/tests/lib/report-translator.js
index f1e00ed3da5..d6d83893234 100644
--- a/tests/lib/report-translator.js
+++ b/tests/lib/report-translator.js
@@ -168,6 +168,15 @@ describe("createReportTranslator", () => {
                 /^context\.report\(\) called with a messageId of '[^']+' which is not present in the 'messages' config:/
             );
         });
+        it("should throw when no message is provided", () => {
+            const reportDescriptor = { node };
+
+            assert.throws(
+                () => translateReport(reportDescriptor),
+                TypeError,
+                "Missing `message` property in report() call; add a message that describes the linting problem."
+            );
+        });
     });
     describe("combining autofixes", () => {
         it("should merge fixes to one if 'fix' function returns an array of fixes.", () => {