chore: improved the config syntax error message

Author: galargh

.changeset/sour-crews-tan.md

@@ -0,0 +1,6 @@
+---
+"@nomicfoundation/hardhat-errors": patch
+"hardhat": patch
+---
+
+Improved the error message for syntax errors found in the config file (https://github.com/NomicFoundation/hardhat/issues/7056)

v-next/hardhat-errors/src/descriptors.ts

@@ -456,6 +456,13 @@ Please add the property "type" with the value "module" in your package.json to e
 
 A fully qualified name should look like file.sol:Contract`,
       },
+      INVALID_CONFIG_FILE: {
+        number: 21,
+        messageTemplate: `Invalid config file at {configPath}:
+{errors}`,
+        websiteTitle: "Invalid config file",
+        websiteDescription: "The config file is invalid.",
+      },
     },
     INTERNAL: {
       ASSERTION_ERROR: {
@@ -2448,7 +2455,7 @@ Possible causes:
 Specify the exact contract using the \`--contract\` flag.`,
         websiteTitle: "Multiple contract matches",
         websiteDescription: `The deployed bytecode matches multiple compiled contracts. Specify the exact contract using the \`--contract\` flag. For example:
-        
+
 \`\`\`sh
 npx hardhat verify --contract contracts/Example.sol:ExampleContract <other args>
 \`\`\`

v-next/hardhat/src/internal/config-loading.ts

@@ -1,5 +1,6 @@
 import type { HardhatUserConfig } from "../types/config.js";
 
+import path from "node:path";
 import { fileURLToPath, pathToFileURL } from "node:url";
 
 import { HardhatError } from "@nomicfoundation/hardhat-errors";
@@ -140,29 +141,56 @@ async function normalizeConfigPath(configPath: string): Promise<string> {
  */
 async function importConfigFileWithTsxFallback(configPath: string) {
   try {
-    return await import(configPath);
-  } catch (error) {
-    ensureError(error);
+    try {
+      return await import(configPath);
+    } catch (error) {
+      ensureError(error);
 
-    if (
-      "code" in error &&
-      error.code === "ERR_UNKNOWN_FILE_EXTENSION" &&
-      configPath.endsWith(".ts")
-    ) {
-      const realPath = await getRealPath(fileURLToPath(configPath));
+      if (
+        "code" in error &&
+        error.code === "ERR_UNKNOWN_FILE_EXTENSION" &&
+        configPath.endsWith(".ts")
+      ) {
+        const realPath = await getRealPath(fileURLToPath(configPath));
 
-      if (compiledConfigFile.has(realPath)) {
-        return compiledConfigFile.get(realPath);
-      }
+        if (compiledConfigFile.has(realPath)) {
+          return compiledConfigFile.get(realPath);
+        }
+
+        const { tsImport } = await import("tsx/esm/api");
+        const config = await tsImport(configPath, import.meta.url);
 
-      const { tsImport } = await import("tsx/esm/api");
-      const config = tsImport(configPath, import.meta.url);
+        compiledConfigFile.set(realPath, config);
 
-      compiledConfigFile.set(realPath, config);
+        return config;
+      }
 
-      return config;
+      throw error;
     }
+  } catch (error) {
+    ensureError(error);
 
-    throw error;
+    switch (error.name) {
+      case "TransformError":
+        const errors = error.message
+          .split("\n")
+          .filter((line) => line.includes(path.basename(configPath)))
+          // For example: /.../hardhat.config.ts:86:5: ERROR: Expected "}" but found "\"community-plugin\""
+          .map((line) => line.split(":"))
+          .map(
+            ([_path, line, _char, _code, ...message]) =>
+              `* Syntax error in line ${line}: ${message.join(":").trim()}`,
+          );
+
+        throw new HardhatError(
+          HardhatError.ERRORS.CORE.GENERAL.INVALID_CONFIG_FILE,
+          {
+            configPath,
+            errors: `\t${errors.join("\n\t")}`,
+          },
+        );
+      default:
+        throw error;
+    }
   }
 }