# LWC1709

Represents a syntax error when parsing a file.

Severity: Fatal

# Message

Syntax error encountered while parsing file {0}. Cause: {1}

The error message includes two placeholders:

{0} is the file path
{1} contains the specific parser error details

Example diagnostic messages:

LWC1709: Syntax error encountered while parsing file c/myComponent/myComponent.js. Cause: Unterminated string constant. (5:12)
LWC1709: Syntax error encountered while parsing file c/myComponent/myComponent.css. Cause: Unclosed block
LWC1709: Syntax error encountered while parsing file c/myComponent/myComponent.html. Cause: Parser internal error

# Problem

LWC1709 occurs when the parser encounters invalid syntax while parsing JavaScript/Typescript, CSS, or HTML template files. This error wraps parsing failures from Babel (for JavaScript/TypeScript), the template compiler (for HTML), or the CSS parser, with the specific error details provided in the message.

# Examples

LWC1709 is a wrapper error that occurs when parsers (Babel for JavaScript/TypeScript, CSS parser for stylesheets, template parser for HTML) encounter syntax that prevents successful parsing. The specific parsing error details are provided in the "Cause" portion of the error message. This error indicates fundamental syntax issues that prevent the compiler from building an Abstract Syntax Tree (AST) or parsing the file structure.

Note

For Javascript and Typescript files, LWC1709 typically only occurs when setting config bundletype to internal, which skips the linting step. It can also occur when you use @lwc/metadata's collectBundleMetadata() function directly, which bypasses linting.

# 1. JavaScript/TypeScript Parser Errors (Babel)

Babel's parse() function encounters syntax that prevents building an AST.

1.1. Literal Errors

Unterminated string literals (missing quotes)
Unterminated template literals (missing backticks)
Invalid escape sequences in strings
Malformed unicode escape sequences
Unterminated regular expressions
Invalid regular expression patterns

1.2. Import/Export Errors

Missing closing braces in import statements
Malformed import/export syntax
Invalid module specifiers

1.3. Structural Errors

Missing or mismatched brackets []
Missing or mismatched braces {}
Missing or mismatched parentheses ()
Incomplete class declarations
Missing class body

1.4. Decorator Errors

Invalid decorator syntax (numbers, special chars)
Decorators in invalid positions
Malformed decorator expressions

1.5. Expression Errors

Incomplete object literals
Invalid property syntax
Malformed expressions
Unexpected tokens

# Examples with Errors

Here's an example that returns error code LWC1709.

Unclosed string literal (missing closing quote):

import { LightningElement } from 'lwc';

export default class MyComponent extends LightningElement {
    message = "Hello World;
}

Error Message: LWC1709: Syntax error encountered while parsing file. Cause: Unterminated string constant.

Unclosed template literal:

import { LightningElement } from 'lwc';

export default class MyComponent extends LightningElement {
    message = `Hello ${this.name};
}

Error Message: LWC1709: Syntax error encountered while parsing file. Cause: Unterminated template.

Unclosed character class in regex:

import { LightningElement } from 'lwc';

export default class MyComponent extends LightningElement {
    pattern = /[abc/;
}

Error Message: LWC1709: Syntax error encountered while parsing file. Cause: Unterminated regular expression.

Missing closing brace in import:

import { LightningElement from 'lwc';

export default class MyComponent extends LightningElement {
    value = 'test';
}

Error Message: LWC1709: Syntax error encountered while parsing file. Cause: Unexpected token, expected ",".

Missing closing brace in object literal:

import { LightningElement } from 'lwc';

export default class MyComponent extends LightningElement {
    config = { key: 'value';
}

Error Message: LWC1709: Syntax error encountered while parsing file. Cause: Unexpected token, expected ",".

Missing closing brace in class:

import { LightningElement } from 'lwc';

export default class MyComponent extends LightningElement {
    handleClick() {
        console.log('clicked');

Error Message: LWC1709: Syntax error encountered while parsing file. Cause: Unexpected token, expected "}".

Incomplete class extends clause:

import { LightningElement } from 'lwc';

export default class MyComponent extends {
    value = 'test';
}

Error Message: LWC1709: Syntax error encountered while parsing file. Cause: Unexpected token, expected "{".

Invalid decorator syntax:

import { LightningElement } from 'lwc';

export default class MyComponent extends LightningElement {
    @123
    myProperty;
}

Error Message: LWC1709: Syntax error encountered while parsing file. Cause: Unexpected token.

# Error Resolution Examples

Here are several ways to fix error code LWC1709.

Close string literal properly:

import { LightningElement } from 'lwc';

export default class MyComponent extends LightningElement {
    message = "Hello World";
}

Close template literal properly:

import { LightningElement } from 'lwc';

export default class MyComponent extends LightningElement {
    message = `Hello ${this.name}`;
}

Close character class properly:

import { LightningElement } from 'lwc';

export default class MyComponent extends LightningElement {
    pattern = /[abc]/;
}

Close import with proper brace:

import { LightningElement } from 'lwc';

export default class MyComponent extends LightningElement {
    value = 'test';
}

Use proper object literal:

import { LightningElement } from 'lwc';

export default class MyComponent extends LightningElement {
    config = { key: 'value' };
}

Close braces properly:

import { LightningElement } from 'lwc';

export default class MyComponent extends LightningElement {
    handleClick() {
        console.log('clicked');
    }
}

Use proper class declaration:

import { LightningElement } from 'lwc';

export default class MyComponent extends LightningElement {
    value = 'test';
}

Use valid decorator syntax:

import { LightningElement, api } from 'lwc';

export default class MyComponent extends LightningElement {
    @api myProperty;
}

# 2. CSS Parser Errors

The CSS parser encounters syntax that prevents parsing stylesheets.

2.1. Unclosed Blocks

Missing closing braces in CSS rules
Unclosed blocks in nested structures

2.2. Unclosed Strings

Unterminated string literals in CSS properties

2.3. Unclosed Comments

CSS comments that are never closed (/* ... )

2.4. Invalid Property Syntax

Missing semicolons followed by invalid tokens
Malformed property declarations

2.5. Unclosed Function Parentheses

CSS functions missing closing parentheses
Incomplete function calls, such as linear-gradient( or rotate()

# Examples with Errors

Here's an example that returns error code LWC1704.

Missing closing brace in rule:

.container {
    color: red;
    background: blue;

Error Message: LWC1709: Syntax error encountered while parsing file. Cause: Unclosed block.

Unclosed string in CSS:

.title {
    content: "Hello World;
}

Error Message: LWC1709: Syntax error encountered while parsing file. Cause: Unclosed string.

Unclosed comment:

.header {
    background: blue;
    /* This comment is never closed
    
.footer {
    background: red;
}

Error Message: LWC1709: Syntax error encountered while parsing file. Cause: Unclosed comment.

Missing semicolon with invalid next token:

.box {
    width: 100px
    height: { invalid }
}

Error Message: LWC1709: Syntax error encountered while parsing file. Cause: Unexpected token.

Unclosed parenthesis in function:

.gradient {
    background: linear-gradient(to right, red, blue;
}

Error Message: LWC1709: Syntax error encountered while parsing file. Cause: Unclosed parenthesis.

# Error Resolution Examples

Here are several ways to fix error code LWC1709.

Close rule properly:

.container {
    color: red;
    background: blue;
}

Close string properly:

.title {
    content: "Hello World";
}

Close comment properly:

.header {
    background: blue;
    /* This is a proper comment */
}

.footer {
    background: red;
}

Use proper property syntax:

.box {
    width: 100px;
    height: 200px;
}

Close function properly:

.gradient {
    background: linear-gradient(to right, red, blue);
}

# 3. HTML Template Parser Errors (Rare)

Template parser errors with error code LWC1709 are very rare as the template compiler handles most invalid HTML gracefully with different error codes. It occurs only when template parser crashes unexpectedly.

3.1. Parser Crashes

Internal parser bugs
Extreme edge cases
Corrupted or malformed input causing parser failure

# LWC1709 Suggested Fix Steps

Consider these suggestions to fix LWC1709 errors.

# Step 1: Identify the File and Error Location

Read the full LWC1709 diagnostic message carefully
Identify the file path, line number, and column number
Open the file in your editor and navigate to the error location
Look at the specific "Cause" message for the exact parsing error
Try fixing the highlighted errors

# Step 2: Use Development Tools

IDE Support:

Use VS Code with the Salesforce Extension Pack
Enable syntax highlighting and error detection
Look for red squiggly underlines indicating syntax errors
Use bracket matching features (Ctrl/Cmd + Shift + \)

Linting:

Run ESLint on your JavaScript files before compilation
Use Stylelint for CSS files
Enable real-time linting in your IDE

Formatting:

Use Prettier or similar formatters to auto-fix syntax
Formatters can identify and fix bracket/brace mismatches

# Step 3: Validate Incrementally

Comment out recent changes to isolate the problematic code
Uncomment sections gradually to find the exact issue
Test compilation after each fix

Back to Error Codes and Messages

← LWC1704