declare subclasses for TemplateError and TransformError, migrate …

…all implementations to new classes

src/environment.ts

@@ -1,7 +1,8 @@
 import tokenize, { Token } from "./tokenizer.ts";
 
 import type { Loader } from "./loader.ts";
-import { TransformError, transformTemplateCode } from "./transformer.ts";
+import { transformTemplateCode } from "./transformer.ts";
+import { TemplateError, TransformError } from "./errors.ts";
 
 export interface TemplateResult {
   content: string;
@@ -138,19 +139,20 @@ export class Environment {
     if (autoDataVarname) {
       try {
         code = transformTemplateCode(code, dataVarname);
-      } catch (error) {
-        if (error instanceof TransformError) {
-          throw this.createError(path, source, error.pos, error);
+      } catch (cause) {
+        if (cause instanceof TransformError) {
+          throw new TemplateError(path, source, cause.position, cause);
         }
 
-        throw error;
+        throw new Error(`Unknown error while transforming ${path}`, { cause });
       }
     }
 
     const constructor = new Function(
       "__file",
       "__env",
       "__defaults",
+      "__err",
       `return${sync ? "" : " async"} function (${dataVarname}) {
         let __pos = 0;
         try {
@@ -160,13 +162,13 @@ export class Environment {
           return __exports;
         } catch (cause) {
           const template = __env.cache.get(__file);
-          throw __env.createError(__file, template?.source || "", __pos, cause);
+          throw new __err(__file, template?.source, __pos, cause);
         }
       }
       `,
     );
 
-    const template: Template = constructor(path, this, defaults);
+    const template: Template = constructor(path, this, defaults, TemplateError);
     template.file = path;
     template.code = code;
     template.source = source;
@@ -179,7 +181,7 @@ export class Environment {
     const { position, error } = result;
 
     if (error) {
-      throw this.createError(path, source, position, error);
+      throw new TemplateError(path, source, position, error);
     }
 
     for (const tokenPreprocessor of this.tokenPreprocessors) {
@@ -310,22 +312,6 @@ export class Environment {
 
     return output;
   }
-
-  createError(
-    path: string = "unknown",
-    source: string = "<empty file>",
-    position: number = 0,
-    cause: Error,
-  ): Error {
-    const [line, column, code] = errorLine(source, position);
-
-    return new Error(
-      `Error in the template ${path}:${line}:${column}\n\n${code.trim()}\n\n${
-        cause.message.replaceAll(/^/gm, "> ")
-      }\n`,
-      { cause },
-    );
-  }
 }
 
 function isGlobal(name: string) {
@@ -341,33 +327,6 @@ function isGlobal(name: string) {
   }
 }
 
-/** Returns the number and code of the errored line */
-export function errorLine(
-  source: string,
-  pos: number,
-): [number, number, string] {
-  let line = 1;
-  let column = 1;
-
-  for (let index = 0; index < pos; index++) {
-    if (
-      source[index] === "\n" ||
-      (source[index] === "\r" && source[index + 1] === "\n")
-    ) {
-      line++;
-      column = 1;
-
-      if (source[index] === "\r") {
-        index++;
-      }
-    } else {
-      column++;
-    }
-  }
-
-  return [line, column, source.split("\n")[line - 1]];
-}
-
 function checkAsync(fn: () => unknown): boolean {
   return fn.constructor?.name === "AsyncFunction";
 }

src/errors.ts

@@ -0,0 +1,66 @@
+class VentoError extends Error {
+  constructor(
+    message?: string,
+    public override cause?: Error,
+  ) {
+    super(message);
+    Error?.captureStackTrace(this, this.constructor);
+    this.name = this.constructor.name;
+  }
+}
+
+export class TemplateError extends VentoError {
+  constructor(
+    public path: string = "<unknown>",
+    public source: string = "<empty file>",
+    public position: number = 0,
+    cause?: Error,
+  ) {
+    const { line, column, code } = errorLine(source, position);
+    super(
+      `Error in template ${path}:${line}:${column}\n\n${code.trim()}\n\n`,
+      cause,
+    );
+
+    if (cause) {
+      this.message += `(via ${cause.name})\n`;
+    }
+  }
+}
+
+export class TransformError extends VentoError {
+  constructor(
+    message: string,
+    public position: number = 0,
+    cause?: Error,
+  ) {
+    super(message, cause);
+  }
+}
+
+/** Returns the number and code of the errored line */
+export function errorLine(
+  source: string,
+  position: number,
+): { line: number; column: number; code: string } {
+  let line = 1;
+  let column = 1;
+
+  for (let index = 0; index < position; index++) {
+    if (
+      source[index] === "\n" ||
+      (source[index] === "\r" && source[index + 1] === "\n")
+    ) {
+      line++;
+      column = 1;
+
+      if (source[index] === "\r") {
+        index++;
+      }
+    } else {
+      column++;
+    }
+  }
+
+  return { line, column, code: source.split("\n")[line - 1] };
+}

src/transformer.ts

@@ -1,6 +1,7 @@
 import { astring, ESTree, meriyah, walker } from "../deps.ts";
+import { TransformError } from "./errors.ts";
 
-// Declare types
+// Declare meriyah's ParseError since it isn't exported
 interface ParseError extends Error {
   start: number;
   end: number;
@@ -9,19 +10,6 @@ interface ParseError extends Error {
   description: string;
 }
 
-interface TransformErrorOptions extends ErrorOptions {
-  pos?: number;
-}
-
-export class TransformError extends Error {
-  pos?: number;
-  constructor(message: string, options?: TransformErrorOptions) {
-    super(message);
-    this.name = "TransformError";
-    this.pos = options?.pos;
-  }
-}
-
 // List of identifiers that are in globalThis
 // but should be accessed as templateState.identifier
 const INCLUDE_GLOBAL = [
@@ -149,18 +137,19 @@ export function transformTemplateCode(
 
     // Use information from `meriyah` to annotate the part of
     // the compiled template function that triggered the ParseError
-    const annotation = code.split("\n")[loc.start.line - 1] + "\n" +
-      " ".repeat(loc.start.column) + "\x1b[31m^\x1b[0m";
+    const annotation = `\u001B[2m${loc.start.line}\u001B[0m ` +
+      code.split("\n")[loc.start.line - 1] +
+      `\n${" ".repeat(loc.start.column)}\u001B[31m^\u001B[39m`;
 
     // Grab the last instance of Vento's `__pos` variable before the
-    // error was thrown. Pass this back to Vento's createError to
+    // error was thrown. Pass this back to Vento to
     // tie this error with problmatic template code
     const matches = [...code.slice(0, start).matchAll(/__pos = (\d+);/g)];
-    const pos = Number(matches.at(-1)?.[1]);
+    const position = Number(matches.at(-1)?.[1]);
 
     throw new TransformError(
-      `[meriyah] ${message}\nthrown while parsing compiled template function:\n\n${annotation}`,
-      { pos },
+      `[meriyah] ${message} while parsing compiled template function:\n\n${annotation}`,
+      position,
     );
   }