unclecode/crawl4ai · error · ValueError

C4A Script compilation error (script {i+1}): Line {error.l

Error message

C4A Script compilation error (script {i+1}):
  Line {error.line}, Column {error.column}: {error.message}
  Code: {error.source_line}
  Suggestion: {error.suggestions[0].message}

What it means

Raised when a js_source entry written in C4A script syntax (crawl4ai's JS DSL) fails to compile. The message includes script index, error line/column, the offending source line, and the first compiler suggestion. This happens during CrawlerRunConfig construction, before any browser launches.

Source

Thrown at crawl4ai/async_configs.py:1981

            # Compile each script
            compiled_js = []
            for i, script in enumerate(scripts):
                result = compile(script)
                
                if result.success:
                    compiled_js.extend(result.js_code)
                else:
                    # Format error message following existing patterns
                    error = result.first_error
                    error_msg = (
                        f"C4A Script compilation error (script {i+1}):\n"
                        f"  Line {error.line}, Column {error.column}: {error.message}\n"
                        f"  Code: {error.source_line}"
                    )
                    if error.suggestions:
                        error_msg += f"\n  Suggestion: {error.suggestions[0].message}"
                        
                    raise ValueError(error_msg)
                    
            self.js_code = compiled_js
            
        except ImportError:
            raise ValueError(
                "C4A script compiler not available. "
                "Please ensure crawl4ai.script module is properly installed."
            )
        except Exception as e:
            # Re-raise with context
            if "compilation error" not in str(e).lower():
                raise ValueError(f"Failed to compile C4A script: {str(e)}")
            raise
    
    def is_match(self, url: str) -> bool:
        """Check if this config matches the given URL.
        
        Args:

View on GitHub (pinned to 7e80152142)

Solutions

1. Read the reported Line/Column and Code — they pinpoint the exact offending token in your js_source entry
2. Apply the included Suggestion from the compiler
3. Verify you are using valid C4A syntax; if you meant plain JavaScript, ensure the string is not being routed through the C4A compiler (check js_source vs js_code usage)
4. Reproduce in isolation: compile just that script with crawl4ai.script's compiler to iterate faster

Example fix

// before
js_source='''wait for "#result" then click it twice and extract title'''
// after  (fix per reported line/column + suggestion)
js_source='''wait for selector "#result"
click "#result" twice'''
// then extract via extraction_strategy

from crawl4ai.script import compile_c4a_script  # name per your version

for i, src in enumerate(js_source_list or []):
    result = compile_c4a_script(src)  # dry-run before building the config
    if not result.success:
        raise SystemExit(f"script {i}: {result.first_error.message}")

try:
    cfg = CrawlerRunConfig(js_source=scripts)
except ValueError as e:
    if "compilation error" in str(e).lower():
        log_script_error(e); exit(2)   # authoring bug: fix the script
    raise

When it happens

Trigger: Including a js_source string with C4A DSL syntax that has a syntax error — wrong keyword, unbalanced brace, invalid selector expression; multiple scripts report their 1-based index.

Common situations: Hand-writing C4A scripts for the first time; editing a working script and introducing a typo; mixing plain JavaScript and C4A DSL syntax in one string.

Related errors

• Failed to compile C4A script: {str(e)}
• Circular include {p}
• Unknown procedure {c.args[0]!r}
• Container not found: ${config.container_selector}
• Timeout after {timeout}ms waiting for selector '{wait_for}'

AI-assisted analysis of unclecode/crawl4ai@7e80152142 (2026-08-14). Data as JSON: /api/errors/9a9bba625d06ed32. Report an issue: GitHub.