feat: catch preprocess errors (#16105)

* feat: catch preprocess error for clearer message

* Update lib/linter/linter.js

Co-authored-by: Milos Djermanovic <milos.djermanovic@gmail.com>

* refactor: code reviews

Co-authored-by: Milos Djermanovic <milos.djermanovic@gmail.com>

Author: JounQin

lib/linter/linter.js

@@ -1510,7 +1510,31 @@ class Linter {
             options.filterCodeBlock ||
             (blockFilename => blockFilename.endsWith(".js"));
         const originalExtname = path.extname(filename);
-        const messageLists = preprocess(text, filenameToExpose).map((block, i) => {
+
+        let blocks;
+
+        try {
+            blocks = preprocess(text, filenameToExpose);
+        } catch (ex) {
+
+            // If the message includes a leading line number, strip it:
+            const message = `Preprocessing error: ${ex.message.replace(/^line \d+:/iu, "").trim()}`;
+
+            debug("%s\n%s", message, ex.stack);
+
+            return [
+                {
+                    ruleId: null,
+                    fatal: true,
+                    severity: 2,
+                    message,
+                    line: ex.lineNumber,
+                    column: ex.column
+                }
+            ];
+        }
+
+        const messageLists = blocks.map((block, i) => {
             debug("A code block was found: %o", block.filename || "(unnamed)");
 
             // Keep the legacy behavior.
@@ -1788,13 +1812,36 @@ class Linter {
         const physicalFilename = options.physicalFilename || filenameToExpose;
         const text = ensureText(textOrSourceCode);
         const preprocess = options.preprocess || (rawText => [rawText]);
-
         const postprocess = options.postprocess || (messagesList => messagesList.flat());
         const filterCodeBlock =
             options.filterCodeBlock ||
             (blockFilename => blockFilename.endsWith(".js"));
         const originalExtname = path.extname(filename);
-        const messageLists = preprocess(text, filenameToExpose).map((block, i) => {
+
+        let blocks;
+
+        try {
+            blocks = preprocess(text, filenameToExpose);
+        } catch (ex) {
+
+            // If the message includes a leading line number, strip it:
+            const message = `Preprocessing error: ${ex.message.replace(/^line \d+:/iu, "").trim()}`;
+
+            debug("%s\n%s", message, ex.stack);
+
+            return [
+                {
+                    ruleId: null,
+                    fatal: true,
+                    severity: 2,
+                    message,
+                    line: ex.lineNumber,
+                    column: ex.column
+                }
+            ];
+        }
+
+        const messageLists = blocks.map((block, i) => {
             debug("A code block was found: %o", block.filename || "(unnamed)");
 
             // Keep the legacy behavior.

tests/lib/linter/linter.js

@@ -6660,6 +6660,31 @@ var a = "test2";
                 assert.strictEqual(preprocess.calledOnce, true);
                 assert.deepStrictEqual(preprocess.args[0], [code, filename]);
             });
+
+            it("should catch preprocess error.", () => {
+                const code = "foo";
+                const preprocess = sinon.spy(() => {
+                    throw Object.assign(new SyntaxError("Invalid syntax"), {
+                        lineNumber: 1,
+                        column: 1
+                    });
+                });
+
+                const messages = linter.verify(code, {}, { filename, preprocess });
+
+                assert.strictEqual(preprocess.calledOnce, true);
+                assert.deepStrictEqual(preprocess.args[0], [code, filename]);
+                assert.deepStrictEqual(messages, [
+                    {
+                        ruleId: null,
+                        fatal: true,
+                        severity: 2,
+                        message: "Preprocessing error: Invalid syntax",
+                        line: 1,
+                        column: 1
+                    }
+                ]);
+            });
         });
 
         describe("postprocessors", () => {
@@ -15158,6 +15183,37 @@ var a = "test2";
                 assert.strictEqual(preprocess.calledOnce, true);
                 assert.deepStrictEqual(preprocess.args[0], [code, filename]);
             });
+
+            it("should catch preprocess error.", () => {
+                const code = "foo";
+                const preprocess = sinon.spy(() => {
+                    throw Object.assign(new SyntaxError("Invalid syntax"), {
+                        lineNumber: 1,
+                        column: 1
+                    });
+                });
+
+                const configs = createFlatConfigArray([
+                    extraConfig
+                ]);
+
+                configs.normalizeSync();
+
+                const messages = linter.verify(code, configs, { filename, preprocess });
+
+                assert.strictEqual(preprocess.calledOnce, true);
+                assert.deepStrictEqual(preprocess.args[0], [code, filename]);
+                assert.deepStrictEqual(messages, [
+                    {
+                        ruleId: null,
+                        fatal: true,
+                        severity: 2,
+                        message: "Preprocessing error: Invalid syntax",
+                        line: 1,
+                        column: 1
+                    }
+                ]);
+            });
         });
 
         describe("postprocessors", () => {