From 9cc7c6b46af23c5219bc67a92b4dc8877ce84c4b Mon Sep 17 00:00:00 2001
From: Alec Aivazis <alec@aivazis.com>
Date: Fri, 25 Jun 2021 19:42:48 -0700
Subject: [PATCH] add line number to parser errors

---
 packages/houdini-common/src/parse.test.ts | 28 +++++++++++++-----
 packages/houdini-common/src/parse.ts      | 35 +++++++++++++++++++----
 2 files changed, 50 insertions(+), 13 deletions(-)

diff --git a/packages/houdini-common/src/parse.test.ts b/packages/houdini-common/src/parse.test.ts
index 009431c15d..90fdbd48a2 100644
--- a/packages/houdini-common/src/parse.test.ts
+++ b/packages/houdini-common/src/parse.test.ts
@@ -341,8 +341,8 @@ describe('parser tests', () => {
 					hello
 				</div>
 			{:else if foo < 4}
-				<!-- 
-					the crazy <div is to trick the parser into thinking there's 
+				<!--
+					the crazy <div is to trick the parser into thinking there's
 					a new tag inside of an expression
 				-->
 				<div attribute={foo > && <div 2} foo>
@@ -364,8 +364,8 @@ describe('parser tests', () => {
 		expect(result.instance?.end).toMatchInlineSnapshot(`undefined`)
 
 		expect(result.module?.content).toMatchInlineSnapshot(`console.log("hello");`)
-		expect(result.module?.start).toMatchInlineSnapshot(`306`)
-		expect(result.module?.end).toMatchInlineSnapshot(`368`)
+		expect(result.module?.start).toMatchInlineSnapshot(`304`)
+		expect(result.module?.end).toMatchInlineSnapshot(`366`)
 
 		checkScriptBounds(doc, result)
 	})
@@ -374,11 +374,11 @@ describe('parser tests', () => {
 		const doc = `<script lang="ts">
 			console.log('hello')
 		</script>
-		
+
 		<header
 			class="sticky flex items-center justify-between h-16 top-0 inset-x-0 max-w-7xl px-2 xl:px-0 mx-auto"
 		>
-			
+
 			<svg
 			class="w-6 h-6"
 			fill="none"
@@ -410,7 +410,7 @@ describe('parser tests', () => {
 		const doc = `<script lang="ts">
 		const example = object({});
 	</script>
-	 
+
 	<div>hello</div>
 	`
 
@@ -446,6 +446,20 @@ describe('parser tests', () => {
 
 		checkScriptBounds(doc, result)
 	})
+
+	test('error messages include line number', () => {
+		try {
+			// parse the string
+			parseFile(`
+				<div`)
+
+			fail('no error thrown')
+		} catch (e) {
+			const message = (e as Error).message
+
+			expect(message).toContain('line 2')
+		}
+	})
 })
 
 function checkScriptBounds(doc: string, result?: ParsedSvelteFile | null | undefined) {
diff --git a/packages/houdini-common/src/parse.ts b/packages/houdini-common/src/parse.ts
index 77bce02223..470a856bcb 100644
--- a/packages/houdini-common/src/parse.ts
+++ b/packages/houdini-common/src/parse.ts
@@ -11,6 +11,8 @@ export type ParserOpts = {
 	filename?: string
 }
 
+type ParserError = { message: string; lineNumber: number }
+
 export function parseFile(str: string, opts?: ParserOpts): ParsedSvelteFile {
 	// look for the instance and module scripts
 	let instance: StackElement | null
@@ -20,13 +22,18 @@ export function parseFile(str: string, opts?: ParserOpts): ParsedSvelteFile {
 		instance = result.instance
 		module = result.module
 	} catch (e) {
+		// pull the message and line number out of the erro
+		const { message, lineNumber } = e as ParserError
+
 		// do we have a filename
 		const filename = opts?.filename || 'testFile'
-		// get the error message
-		const message = (e as Error).message || e
 
 		// bubble the error up
-		throw new Error(`Encountered error while parsing ${filename}: ${message}`)
+		throw new Error(
+			`Encountered error${
+				lineNumber ? ` on line ${lineNumber}` : ''
+			} while parsing ${filename}: ${message}`
+		)
 	}
 
 	// build up the result
@@ -78,10 +85,26 @@ function parse(str: string): { instance: StackElement | null; module: StackEleme
 	let module: StackElement | null = null
 	let instance: StackElement | null = null
 
+	// count the number of lines
+	let lineNumber = 1
+
+	const ErrorWithLineNumber = (message: string) => {
+		return {
+			message,
+			lineNumber,
+		}
+	}
+
 	const pop = () => {
 		const head = content.slice(0, 1)
 		content = content.slice(1, content.length)
 		index++
+
+		// if we found a newline, increment the line count
+		if (head === '\n') {
+			lineNumber++
+		}
+
 		return head
 	}
 
@@ -105,7 +128,7 @@ function parse(str: string): { instance: StackElement | null; module: StackEleme
 
 		// if the last character is not what we were looking for
 		if (tail !== char) {
-			throw new Error('could not find ' + char)
+			throw ErrorWithLineNumber('could not find ' + char)
 		}
 
 		return acc
@@ -131,7 +154,7 @@ function parse(str: string): { instance: StackElement | null; module: StackEleme
 
 		// if the last character we saw was not the finishing character, there was a problem
 		if (head !== finish) {
-			throw new Error(`did not encounter matching ${finish}.`)
+			throw ErrorWithLineNumber(`did not encounter matching ${finish}.`)
 		}
 	}
 
@@ -166,7 +189,7 @@ function parse(str: string): { instance: StackElement | null; module: StackEleme
 				const innerElement = stack.pop()
 				const tagName = tag.substr(1)
 				if (!innerElement || innerElement.tag !== parseTag(tagName).tag) {
-					throw new Error(
+					throw ErrorWithLineNumber(
 						`unexpected closing tag ${parseTag(tagName).tag}, expected ${
 							innerElement?.tag
 						}.`