From 8f797e637c6c79a126993d22a07a652d7a89f432 Mon Sep 17 00:00:00 2001
From: Noel Forte <noel@forte.is>
Date: Sat, 23 Nov 2024 17:26:25 -0500
Subject: [PATCH 01/13] declare correct type for `ESTree` nodes

---
 src/transformer.ts | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/src/transformer.ts b/src/transformer.ts
index 551e1ec..d855e9f 100644
--- a/src/transformer.ts
+++ b/src/transformer.ts
@@ -166,7 +166,7 @@ export function transformTemplateCode(
   }
 
   walker.walk(parsed, {
-    enter(node) {
+    enter(node: ESTree.Node) {
       switch (node.type) {
         // Track variable declarations
         case "VariableDeclaration":

From 300918fba118824f49dfbe30e63070260eaf17f8 Mon Sep 17 00:00:00 2001
From: Noel Forte <noel@forte.is>
Date: Sat, 23 Nov 2024 17:51:12 -0500
Subject: [PATCH 02/13] temporary patch: dnt throws error for
 `jsr:@std/path@1.0.8`, reverting to `deno.land` URL instead

---
 deps.ts | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/deps.ts b/deps.ts
index 5b86a25..8120f72 100644
--- a/deps.ts
+++ b/deps.ts
@@ -1,4 +1,4 @@
-export * as path from "jsr:@std/path@1.0.8";
+export * as path from "https://deno.land/std@0.224.0/path/mod.ts";
 export * as html from "jsr:@std/html@1.0.3";
 
 export * as astring from "jsr:@davidbonnet/astring@1.8.6";

From 167fd66dd458c567e730d3a426f662119cd93adf Mon Sep 17 00:00:00 2001
From: Noel Forte <noel@forte.is>
Date: Sat, 23 Nov 2024 21:54:41 -0500
Subject: [PATCH 03/13] move `ParseError` to transformer.ts

---
 src/environment.ts |  8 ++------
 src/transformer.ts | 10 ++++++++++
 2 files changed, 12 insertions(+), 6 deletions(-)

diff --git a/src/environment.ts b/src/environment.ts
index bfa4c72..cb49ad8 100644
--- a/src/environment.ts
+++ b/src/environment.ts
@@ -1,7 +1,7 @@
 import tokenize, { Token } from "./tokenizer.ts";
 
 import type { Loader } from "./loader.ts";
-import { transformTemplateCode } from "./transformer.ts";
+import { transformTemplateCode, type ParseError} from "./transformer.ts";
 
 export interface TemplateResult {
   content: string;
@@ -387,8 +387,4 @@ function checkAsync(fn: () => unknown): boolean {
   return fn.constructor?.name === "AsyncFunction";
 }
 
-interface ParseError extends Error {
-  start: number;
-  end: number;
-  range: [number, number];
-}
+
diff --git a/src/transformer.ts b/src/transformer.ts
index d855e9f..a1bd365 100644
--- a/src/transformer.ts
+++ b/src/transformer.ts
@@ -1,5 +1,15 @@
 import { astring, ESTree, meriyah, walker } from "../deps.ts";
 
+// Declare types
+export interface ParseError extends Error {
+  start: number;
+  end: number;
+  range: [number, number];
+  loc: Record<'start' | 'end', Record<'line' | 'column', number>>;
+  description: string;
+  annotation?: string;
+}
+
 // List of identifiers that are in globalThis
 // but should be accessed as templateState.identifier
 const INCLUDE_GLOBAL = [

From 55c1c47f54b340508ffa813e0eafd0b39ba65a9f Mon Sep 17 00:00:00 2001
From: Noel Forte <noel@forte.is>
Date: Sat, 23 Nov 2024 21:56:20 -0500
Subject: [PATCH 04/13] refactor parse error handling: include substring of
 code that failed parsing

---
 src/environment.ts | 12 +++++++++---
 src/transformer.ts | 20 +++++++++++++++++++-
 2 files changed, 28 insertions(+), 4 deletions(-)

diff --git a/src/environment.ts b/src/environment.ts
index cb49ad8..f3c6bc8 100644
--- a/src/environment.ts
+++ b/src/environment.ts
@@ -139,8 +139,9 @@ export class Environment {
       try {
         code = transformTemplateCode(code, dataVarname);
       } catch (error) {
-        const end = (error as ParseError).start;
-        const lastPos = code.slice(0, end).lastIndexOf("__pos = ");
+        let { start: errorStart, message, annotation } = error as ParseError;
+        
+        const lastPos = code.slice(0, errorStart).lastIndexOf("__pos = ");
         const lastPosEnd = code.slice(lastPos).indexOf(";");
 
         if (lastPos > -1 && lastPosEnd > lastPos) {
@@ -148,11 +149,16 @@ export class Environment {
             code.slice(lastPos + 8, lastPos + lastPosEnd),
             10,
           );
+
+          if (annotation) {
+            message += `\n\nAttempted to parse:\n\n${annotation}`
+          }
+
           throw this.createError(
             path || "",
             source,
             pos,
-            new Error((error as ParseError).message),
+            new Error(message),
           );
         }
 
diff --git a/src/transformer.ts b/src/transformer.ts
index a1bd365..3d8ec81 100644
--- a/src/transformer.ts
+++ b/src/transformer.ts
@@ -129,7 +129,25 @@ export function transformTemplateCode(
     return code;
   }
 
-  const parsed = meriyah.parseScript(code, { module: true }) as ESTree.Program;
+  let parsed;
+  try {
+    parsed = meriyah.parseScript(code, { module: true }) as ESTree.Program;
+  } catch (error) {
+    const { loc } = error as ParseError;
+
+    const lines = code.split('\n');
+
+    lines.splice(loc.start.line, 0, `${' '.repeat(loc.start.column)}\x1b[31m^\x1b[0m`)
+      
+    const annotation = lines.slice(Math.min(0, loc.start.line - 2), Math.min(loc.end.line + 3, lines.length))
+      .join('\n');
+    
+    throw Object.assign(error as ParseError, {
+      message: 'Failed to parse template function',
+      annotation
+    })
+  }
+
   const tracker = new ScopeTracker();
 
   const exclude = [

From 78a3b371e5fef7da225cc19dbbe78de5b1deb9a4 Mon Sep 17 00:00:00 2001
From: Noel Forte <noel@forte.is>
Date: Sun, 24 Nov 2024 01:04:01 -0500
Subject: [PATCH 05/13] clean up implementation of error annotation

---
 src/environment.ts | 12 +++---------
 src/transformer.ts | 19 +++++++------------
 2 files changed, 10 insertions(+), 21 deletions(-)

diff --git a/src/environment.ts b/src/environment.ts
index f3c6bc8..2914df7 100644
--- a/src/environment.ts
+++ b/src/environment.ts
@@ -1,7 +1,7 @@
 import tokenize, { Token } from "./tokenizer.ts";
 
 import type { Loader } from "./loader.ts";
-import { transformTemplateCode, type ParseError} from "./transformer.ts";
+import { type ParseError, transformTemplateCode } from "./transformer.ts";
 
 export interface TemplateResult {
   content: string;
@@ -139,8 +139,8 @@ export class Environment {
       try {
         code = transformTemplateCode(code, dataVarname);
       } catch (error) {
-        let { start: errorStart, message, annotation } = error as ParseError;
-        
+        const { start: errorStart, message } = error as ParseError;
+
         const lastPos = code.slice(0, errorStart).lastIndexOf("__pos = ");
         const lastPosEnd = code.slice(lastPos).indexOf(";");
 
@@ -150,10 +150,6 @@ export class Environment {
             10,
           );
 
-          if (annotation) {
-            message += `\n\nAttempted to parse:\n\n${annotation}`
-          }
-
           throw this.createError(
             path || "",
             source,
@@ -392,5 +388,3 @@ export function errorLine(
 function checkAsync(fn: () => unknown): boolean {
   return fn.constructor?.name === "AsyncFunction";
 }
-
-
diff --git a/src/transformer.ts b/src/transformer.ts
index 3d8ec81..a770850 100644
--- a/src/transformer.ts
+++ b/src/transformer.ts
@@ -5,9 +5,8 @@ export interface ParseError extends Error {
   start: number;
   end: number;
   range: [number, number];
-  loc: Record<'start' | 'end', Record<'line' | 'column', number>>;
+  loc: Record<"start" | "end", Record<"line" | "column", number>>;
   description: string;
-  annotation?: string;
 }
 
 // List of identifiers that are in globalThis
@@ -133,19 +132,15 @@ export function transformTemplateCode(
   try {
     parsed = meriyah.parseScript(code, { module: true }) as ESTree.Program;
   } catch (error) {
-    const { loc } = error as ParseError;
+    const { message, loc: { start } } = error as ParseError;
 
-    const lines = code.split('\n');
+    const annotation = code.split("\n")[start.line - 1] + "\n" +
+      " ".repeat(start.column) + "\x1b[31m^\x1b[0m";
 
-    lines.splice(loc.start.line, 0, `${' '.repeat(loc.start.column)}\x1b[31m^\x1b[0m`)
-      
-    const annotation = lines.slice(Math.min(0, loc.start.line - 2), Math.min(loc.end.line + 3, lines.length))
-      .join('\n');
-    
     throw Object.assign(error as ParseError, {
-      message: 'Failed to parse template function',
-      annotation
-    })
+      message:
+        `Failed to parse template function internally. <template>:${message}\n\n${annotation}`,
+    });
   }
 
   const tracker = new ScopeTracker();

From 5418857b01f0123951828d1486790a61c5a93bae Mon Sep 17 00:00:00 2001
From: Noel Forte <noel@forte.is>
Date: Sat, 30 Nov 2024 22:49:31 -0500
Subject: [PATCH 06/13] move transform error handling to `transformer.ts`

additionally, create an error class for transform errors that can carry `pos` back to environment.ts to pass along to `createError`.
---
 src/environment.ts | 21 +++------------------
 src/transformer.ts | 32 ++++++++++++++++++++++++++------
 2 files changed, 29 insertions(+), 24 deletions(-)

diff --git a/src/environment.ts b/src/environment.ts
index 2914df7..2b2e5e1 100644
--- a/src/environment.ts
+++ b/src/environment.ts
@@ -1,7 +1,7 @@
 import tokenize, { Token } from "./tokenizer.ts";
 
 import type { Loader } from "./loader.ts";
-import { type ParseError, transformTemplateCode } from "./transformer.ts";
+import { TransformError, transformTemplateCode } from "./transformer.ts";
 
 export interface TemplateResult {
   content: string;
@@ -139,23 +139,8 @@ export class Environment {
       try {
         code = transformTemplateCode(code, dataVarname);
       } catch (error) {
-        const { start: errorStart, message } = error as ParseError;
-
-        const lastPos = code.slice(0, errorStart).lastIndexOf("__pos = ");
-        const lastPosEnd = code.slice(lastPos).indexOf(";");
-
-        if (lastPos > -1 && lastPosEnd > lastPos) {
-          const pos = parseInt(
-            code.slice(lastPos + 8, lastPos + lastPosEnd),
-            10,
-          );
-
-          throw this.createError(
-            path || "",
-            source,
-            pos,
-            new Error(message),
-          );
+        if (error instanceof TransformError) {
+          throw this.createError(path || "", source, error.pos, error);
         }
 
         throw error;
diff --git a/src/transformer.ts b/src/transformer.ts
index a770850..4af46b0 100644
--- a/src/transformer.ts
+++ b/src/transformer.ts
@@ -1,7 +1,7 @@
 import { astring, ESTree, meriyah, walker } from "../deps.ts";
 
 // Declare types
-export interface ParseError extends Error {
+interface ParseError extends Error {
   start: number;
   end: number;
   range: [number, number];
@@ -9,6 +9,21 @@ export interface ParseError extends Error {
   description: string;
 }
 
+interface TransformErrorOptions {
+  message: string;
+  pos: number;
+  cause: Error;
+}
+
+export class TransformError extends Error {
+  pos: number;
+  constructor(options: TransformErrorOptions) {
+    super(options.message, { cause: options.cause });
+    this.name = "TransformError";
+    this.pos = options.pos;
+  }
+}
+
 // List of identifiers that are in globalThis
 // but should be accessed as templateState.identifier
 const INCLUDE_GLOBAL = [
@@ -132,14 +147,19 @@ export function transformTemplateCode(
   try {
     parsed = meriyah.parseScript(code, { module: true }) as ESTree.Program;
   } catch (error) {
-    const { message, loc: { start } } = error as ParseError;
+    const { message, start, loc } = error as ParseError;
+
+    const annotation = code.split("\n")[loc.start.line - 1] + "\n" +
+      " ".repeat(loc.start.column) + "\x1b[31m^\x1b[0m";
 
-    const annotation = code.split("\n")[start.line - 1] + "\n" +
-      " ".repeat(start.column) + "\x1b[31m^\x1b[0m";
+    const posMatches = [...code.slice(0, start).matchAll(/__pos = (\d+);/g)];
+    const pos = Number(posMatches.at(-1)?.[1]);
 
-    throw Object.assign(error as ParseError, {
+    throw new TransformError({
       message:
-        `Failed to parse template function internally. <template>:${message}\n\n${annotation}`,
+        `Failed to transform template function internally.\n${message} while transforming:\n\n${annotation}`,
+      cause: error as ParseError,
+      pos,
     });
   }
 

From b92b0aea7504239604f8cc26cade0e7ef8a2335d Mon Sep 17 00:00:00 2001
From: Noel Forte <noel@forte.is>
Date: Sat, 30 Nov 2024 23:23:16 -0500
Subject: [PATCH 07/13] assign default args to `createError`

---
 src/environment.ts | 14 +++++---------
 1 file changed, 5 insertions(+), 9 deletions(-)

diff --git a/src/environment.ts b/src/environment.ts
index 2b2e5e1..606881a 100644
--- a/src/environment.ts
+++ b/src/environment.ts
@@ -140,7 +140,7 @@ export class Environment {
         code = transformTemplateCode(code, dataVarname);
       } catch (error) {
         if (error instanceof TransformError) {
-          throw this.createError(path || "", source, error.pos, error);
+          throw this.createError(path, source, error.pos, error);
         }
 
         throw error;
@@ -179,7 +179,7 @@ export class Environment {
     const { position, error } = result;
 
     if (error) {
-      throw this.createError(path || "unknown", source, position, error);
+      throw this.createError(path, source, position, error);
     }
 
     for (const tokenPreprocessor of this.tokenPreprocessors) {
@@ -312,15 +312,11 @@ export class Environment {
   }
 
   createError(
-    path: string,
-    source: string,
-    position: number,
+    path: string = "unknown",
+    source: string = "<empty file>",
+    position: number = 0,
     cause: Error,
   ): Error {
-    if (!source) {
-      return cause;
-    }
-
     const [line, column, code] = errorLine(source, position);
 
     return new Error(

From 650541e283908dd28ed2cfc44ea822571e06825f Mon Sep 17 00:00:00 2001
From: Noel Forte <noel@forte.is>
Date: Sat, 30 Nov 2024 23:27:51 -0500
Subject: [PATCH 08/13] prepend all multiline error message lines with `>`

---
 src/environment.ts | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/src/environment.ts b/src/environment.ts
index 606881a..9e44401 100644
--- a/src/environment.ts
+++ b/src/environment.ts
@@ -320,7 +320,7 @@ export class Environment {
     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}\n`,
+      `Error in the template ${path}:${line}:${column}\n\n${code.trim()}\n\n${cause.message.replaceAll(/^/gm, '> ')}\n`,
       { cause },
     );
   }

From 5f2814db72f0c111bd5aabca89f26d6352b79aaa Mon Sep 17 00:00:00 2001
From: Noel Forte <noel@forte.is>
Date: Sat, 30 Nov 2024 23:28:09 -0500
Subject: [PATCH 09/13] shorten transform error message

---
 src/transformer.ts | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/src/transformer.ts b/src/transformer.ts
index 4af46b0..ee559a1 100644
--- a/src/transformer.ts
+++ b/src/transformer.ts
@@ -157,7 +157,7 @@ export function transformTemplateCode(
 
     throw new TransformError({
       message:
-        `Failed to transform template function internally.\n${message} while transforming:\n\n${annotation}`,
+        `Error transforming template function.\n${message} while transforming:\n\n${annotation}`,
       cause: error as ParseError,
       pos,
     });

From 24ec56db5f60e2929e65a6ea8223d61832d49f6a Mon Sep 17 00:00:00 2001
From: Noel Forte <noel@forte.is>
Date: Sun, 1 Dec 2024 15:54:55 -0500
Subject: [PATCH 10/13] remove `meriyah` error stack trace from
 `TransformError` constructor and refactor options interface to extend the
 default ErrorOptions

---
 src/environment.ts |  4 +++-
 src/transformer.ts | 24 ++++++++++--------------
 2 files changed, 13 insertions(+), 15 deletions(-)

diff --git a/src/environment.ts b/src/environment.ts
index 9e44401..cd5040f 100644
--- a/src/environment.ts
+++ b/src/environment.ts
@@ -320,7 +320,9 @@ export class Environment {
     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`,
+      `Error in the template ${path}:${line}:${column}\n\n${code.trim()}\n\n${
+        cause.message.replaceAll(/^/gm, "> ")
+      }\n`,
       { cause },
     );
   }
diff --git a/src/transformer.ts b/src/transformer.ts
index ee559a1..3dde0aa 100644
--- a/src/transformer.ts
+++ b/src/transformer.ts
@@ -9,18 +9,16 @@ interface ParseError extends Error {
   description: string;
 }
 
-interface TransformErrorOptions {
-  message: string;
-  pos: number;
-  cause: Error;
+interface TransformErrorOptions extends ErrorOptions {
+  pos?: number;
 }
 
 export class TransformError extends Error {
-  pos: number;
-  constructor(options: TransformErrorOptions) {
-    super(options.message, { cause: options.cause });
+  pos?: number;
+  constructor(message: string, options?: TransformErrorOptions) {
+    super(message);
     this.name = "TransformError";
-    this.pos = options.pos;
+    this.pos = options?.pos;
   }
 }
 
@@ -155,12 +153,10 @@ export function transformTemplateCode(
     const posMatches = [...code.slice(0, start).matchAll(/__pos = (\d+);/g)];
     const pos = Number(posMatches.at(-1)?.[1]);
 
-    throw new TransformError({
-      message:
-        `Error transforming template function.\n${message} while transforming:\n\n${annotation}`,
-      cause: error as ParseError,
-      pos,
-    });
+    throw new TransformError(
+      `Error transforming template function.\n${message} while transforming:\n\n${annotation}`,
+      { cause: error as ParseError, pos },
+    );
   }
 
   const tracker = new ScopeTracker();

From a9ed438e8e8e3e4bc32cf645752e5dad1665aa26 Mon Sep 17 00:00:00 2001
From: Noel Forte <noel@forte.is>
Date: Sun, 1 Dec 2024 15:58:01 -0500
Subject: [PATCH 11/13] rename variable `posMatches` to `matches` to follow
 naming convention in other areas of module

---
 src/transformer.ts | 4 ++--
 1 file changed, 2 insertions(+), 2 deletions(-)

diff --git a/src/transformer.ts b/src/transformer.ts
index 3dde0aa..d254f7a 100644
--- a/src/transformer.ts
+++ b/src/transformer.ts
@@ -150,8 +150,8 @@ export function transformTemplateCode(
     const annotation = code.split("\n")[loc.start.line - 1] + "\n" +
       " ".repeat(loc.start.column) + "\x1b[31m^\x1b[0m";
 
-    const posMatches = [...code.slice(0, start).matchAll(/__pos = (\d+);/g)];
-    const pos = Number(posMatches.at(-1)?.[1]);
+    const matches = [...code.slice(0, start).matchAll(/__pos = (\d+);/g)];
+    const pos = Number(matches.at(-1)?.[1]);
 
     throw new TransformError(
       `Error transforming template function.\n${message} while transforming:\n\n${annotation}`,

From ca834ee60ffb196ae0a08709ae9002d40e1e0c5b Mon Sep 17 00:00:00 2001
From: Noel Forte <noel@forte.is>
Date: Sun, 1 Dec 2024 16:01:00 -0500
Subject: [PATCH 12/13] convert all thrown errors in `transformer.ts` to
 `TransformError` instances prefixed with `[meriyah]` to indicate source of
 error

---
 src/transformer.ts | 8 ++++----
 1 file changed, 4 insertions(+), 4 deletions(-)

diff --git a/src/transformer.ts b/src/transformer.ts
index d254f7a..31974c5 100644
--- a/src/transformer.ts
+++ b/src/transformer.ts
@@ -154,8 +154,8 @@ export function transformTemplateCode(
     const pos = Number(matches.at(-1)?.[1]);
 
     throw new TransformError(
-      `Error transforming template function.\n${message} while transforming:\n\n${annotation}`,
-      { cause: error as ParseError, pos },
+      `[meriyah] ${message}\nthrown while parsing compiled template function:\n\n${annotation}`,
+      { pos },
     );
   }
 
@@ -167,11 +167,11 @@ export function transformTemplateCode(
   ];
 
   if (parsed.type !== "Program") {
-    throw new Error("Expected a program");
+    throw new TransformError("[meriyah] Expected a program");
   }
 
   if (parsed.body.length === 0) {
-    throw new Error("Empty program");
+    throw new TransformError("[meriyah] Empty program");
   }
 
   // Transforms an identifier to a MemberExpression

From 0fe3383b96c7cacef802f8f368d53a83cb132294 Mon Sep 17 00:00:00 2001
From: Noel Forte <noel@forte.is>
Date: Sun, 1 Dec 2024 16:20:48 -0500
Subject: [PATCH 13/13] add comments to `TransformError`-generating code

---
 src/transformer.ts | 5 +++++
 1 file changed, 5 insertions(+)

diff --git a/src/transformer.ts b/src/transformer.ts
index 31974c5..73355f6 100644
--- a/src/transformer.ts
+++ b/src/transformer.ts
@@ -147,9 +147,14 @@ export function transformTemplateCode(
   } catch (error) {
     const { message, start, loc } = error as ParseError;
 
+    // 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";
 
+    // Grab the last instance of Vento's `__pos` variable before the
+    // error was thrown. Pass this back to Vento's createError 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]);