Add config validation for empty network url

Author: kshyun28

packages/hardhat-core/src/internal/core/config/config-validation.ts

@@ -58,6 +58,12 @@ function getMessage(e: ValidationError): string {
       );
 }
 
+function getEmptyErrorMessage(path: string, value: any, expectedType: string) {
+  return `Empty value ${stringify(
+    value
+  )} for ${path} - Expected a non-empty value of type ${expectedType}.`;
+}
+
 function getErrorMessage(path: string, value: any, expectedType: string) {
   return `Invalid value ${stringify(
     value
@@ -148,6 +154,14 @@ function isDecimalString(v: unknown): v is string {
   return v.match(DEC_STRING_REGEX) !== null;
 }
 
+function isEmptyString(v: unknown): v is string {
+  if (typeof v !== "string") {
+    return false;
+  }
+
+  return v.trim().length === 0;
+}
+
 export const hexString = new t.Type<string>(
   "hex string",
   isHexString,
@@ -535,6 +549,14 @@ export function getValidationErrors(config: any): string[] {
               "string"
             )
           );
+        } else if (isEmptyString(netConfig.url)) {
+          errors.push(
+            getEmptyErrorMessage(
+              `HardhatConfig.networks.${networkName}.url`,
+              netConfig.url,
+              "string"
+            )
+          );
         }
       }
 

packages/hardhat-core/test/internal/core/config/config-validation.ts

@@ -1171,6 +1171,20 @@ describe("Config validation", function () {
             );
           });
 
+          it("Should fail if an empty url is set for custom networks", function () {
+            // Empty string
+            expectHardhatError(
+              () => validateConfig({ networks: { custom: { url: "" } } }),
+              ERRORS.GENERAL.INVALID_CONFIG
+            );
+
+            // Empty string with at least 1 whitespace
+            expectHardhatError(
+              () => validateConfig({ networks: { custom: { url: " " } } }),
+              ERRORS.GENERAL.INVALID_CONFIG
+            );
+          });
+
           it("Shouldn't fail if no url is set for localhost network", function () {
             const errors = getValidationErrors({ networks: { localhost: {} } });
             assert.isEmpty(errors);