Improve error rendering, add support for subErrors

package.json

@@ -27,7 +27,9 @@
     "create-error": "^0.3.1",
     "default-value": "^1.0.0",
     "flatten": "^1.0.3",
-    "is-arguments": "^1.0.4"
+    "indent-string": "^4.0.0",
+    "is-arguments": "^1.0.4",
+    "supports-color": "^7.1.0"
   },
   "devDependencies": {
     "@joepie91/eslint-config": "^1.1.0",

src/aggregrate-errors.js

@@ -1,5 +1,7 @@
 "use strict";
 
+const indentString = require("indent-string");
+const supportsColor = require("supports-color");
 const matchVirtualProperty = require("@validatem/match-virtual-property");
 
 const AggregrateValidationError = require("./aggregrate-validation-error");
@@ -7,38 +9,69 @@ const AggregrateValidationError = require("./aggregrate-validation-error");
 // TODO: Omit the "At (root)" for path-less errors, to avoid confusion when singular values are being compared?
 // TODO: Move out the path generating logic into a separate module, to better support custom error formatting code
 
-module.exports = function aggregrateAndThrowErrors(errors) {
-	let rephrasedErrors = errors.map((error) => {
-		let stringifiedPathSegments = error.path.map((segment) => {
+function joinPathSegments(segments) {
+	return (segments.length > 0)
+		? segments.join(" -> ")
+		: "(root)";
+}
+
+// NOTE: We do some manual ANSI escape code stuff here for now, because using `chalk` would significantly inflate the bundle size of the core.
+// TODO: Find a better solution for this.
+let openHighlight, openDim, closeColor;
+
+if (supportsColor.stderr) {
+	openHighlight = `\u001b[36m`; // cyan
+	openDim = `\u001b[90m`; // gray
+	closeColor = `\u001b[39m`;
+} else {
+	openHighlight = "";
+	openDim = "";
+	closeColor = "";
+}
+
+function renderErrorList(errors, basePath = []) {
+	let rephrasedErrors = errors.map((error, i) => {
+		let pathSegments = error.path.map((segment) => {
 			if (segment == null) {
 				throw new Error(`Unexpected empty path segment encountered; this is a bug, please report it!`);
-			} else if (typeof segment === "string") {
-				return segment;
-			} else if (typeof segment === "number") {
-				return String(segment);
+			} else if (typeof segment === "string" || typeof segment === "number") {
+				return openHighlight + String(segment) + closeColor;
 			} else if (matchVirtualProperty(segment)) {
-				return `(${segment.name})`;
+				return openDim + `(${segment.name})` + closeColor;
 			} else {
 				throw new Error(`Unexpected path segment encountered: ${segment}; this is a bug, please report it!`);
 			}
-		});
+		});		
 
-		/* TODO: Make immutable */
-		let path = (stringifiedPathSegments.length > 0)
-			? stringifiedPathSegments.join(" -> ")
-			: "(root)";
+		let lineCharacter = (i < errors.length - 1)
+			? "├─"
+			: "└─";
 
-		error.message = `At ${path}: ${error.message}`;
-		return error;
+		let mainLine = (basePath.length > 0)
+			// ? `... -> ${joinPathSegments(pathSegments)}: ${error.message}`
+			? `    ${lineCharacter} ${joinPathSegments(pathSegments)}: ${error.message}`
+			: ` - At ${joinPathSegments(pathSegments)}: ${error.message}`;
+
+		if (error.subErrors != null && error.subErrors.length > 0) {
+			let renderedSubErrors = renderErrorList(error.subErrors, error.path);
+
+			return mainLine + "\n" + indentString(renderedSubErrors, 2);
+		} else {
+			return mainLine;
+		}
 	});
 
-	let detailLines = rephrasedErrors.map((error) => {
-		return ` - ${error.message}`;
+	return rephrasedErrors.map((error) => {
+		return `${error}`;
 	}).join("\n");
+}
+
+module.exports = function aggregrateAndThrowErrors(errors) {
+	let detailLines = renderErrorList(errors);
 
 	if (errors.length > 0) {
 		return new AggregrateValidationError(`One or more validation errors occurred:\n${detailLines}`, {
-			errors: rephrasedErrors
+			errors: errors
 		});
 	}
 };

yarn.lock

@@ -697,6 +697,11 @@ imurmurhash@^0.1.4:
   resolved "https://registry.yarnpkg.com/imurmurhash/-/imurmurhash-0.1.4.tgz#9218b9b2b928a238b13dc4fb6b6d576f231453ea"
   integrity sha1-khi5srkoojixPcT7a21XbyMUU+o=
 
+indent-string@^4.0.0:
+  version "4.0.0"
+  resolved "https://registry.yarnpkg.com/indent-string/-/indent-string-4.0.0.tgz#624f8f4497d619b2d9768531d58f4122854d7251"
+  integrity sha512-EdDDZu4A2OyIK7Lr/2zG+w5jmbuk1DVBnEwREQvBzspBJkCEbRa8GxU1lghYcaGJCnRWibjDXlq779X1/y5xwg==
+
 inflight@^1.0.4:
   version "1.0.6"
   resolved "https://registry.yarnpkg.com/inflight/-/inflight-1.0.6.tgz#49bd6331d7d02d0c09bc910a1075ba8165b56df9"