{"record":{"id":"3f388927c0ceb5e5","repo":"getzola/zola","slug":"could-not-build-error-response","errorCode":null,"errorMessage":"Could not build error response","messagePattern":"Could not build error response","errorType":"panic","errorClass":null,"httpStatus":null,"severity":"info","filePath":"src/cmd/serve.rs","lineNumber":340,"sourceCode":" r#\"
Zola Build Error:
{error_str}
\"#\n );\n\n if is_html {\n // Inject error dialog into existing HTML response\n let mut new_bytes = bytes;\n new_bytes.extend(html_error.as_bytes());\n return Response::from_parts(parts, Body::from(new_bytes));\n } else if is_not_found {\n // Return a full HTML page with the error dialog for 404s\n // Include livereload.js so the page can receive reload messages when the error is fixed\n let html_page = format!(\n r#\"Zola Build Error{html_error}\"#\n );\n return Response::builder()\n .header(header::CONTENT_TYPE, \"text/html\")\n .status(StatusCode::OK)\n .body(Body::from(html_page))\n .expect(\"Could not build error response\");\n }\n }\n\n Response::from_parts(parts, Body::from(bytes))\n}\n\nfn in_memory_content(path: &RelativePathBuf, content: &str) -> Response {\n let content_type = match path.extension() {\n Some(ext) => match ext {\n \"xml\" => \"text/xml\",\n \"json\" => \"application/json\",\n \"txt\" => \"text/plain\",\n _ => \"text/html\",\n },\n None => \"text/html\",\n };\n Response::builder()\n .header(header::CONTENT_TYPE, content_type)","sourceCodeStart":322,"sourceCodeEnd":358,"githubUrl":"https://github.com/getzola/zola/blob/61d30828217957120309db657950224edf9707e2/src/cmd/serve.rs#L322-L358","documentation":"error_injection_middleware constructs an HTML error page response for build errors with Response::builder().body(...).expect(\"Could not build error response\"). The builder only fails if a header value or body conversion is invalid; with the current static headers this is an invariant panic path in the dev server.","triggerScenarios":"`zola serve` with a build error whose injected html_error content causes the response builder to fail — e.g. after modifying the code to add invalid header values; otherwise unreachable with static headers.","commonSituations":"Customizing the middleware (e.g. adding a content-security-policy header built from dynamic strings) and hitting a hyper HeaderValue parse failure while a rebuild error page is shown.","solutions":["Use HeaderValue::from_static/from_bytes-checked values for any custom header","Construct the response with Response::new and headers_mut() to avoid the fallible builder","Sanitize/validate dynamic header content before injecting it"],"exampleFix":"// before\nreturn Response::builder()\n .header(header::CONTENT_TYPE, \"text/html\")\n .status(StatusCode::OK)\n .body(Body::from(html_page))\n .expect(\"Could not build error response\");\n// after\nlet mut response = Response::new(Body::from(html_page));\n*response.status_mut() = StatusCode::OK;\nresponse.headers_mut().insert(header::CONTENT_TYPE, HeaderValue::from_static(\"text/html\"));\nreturn response;","handlingStrategy":"fallback","validationCode":"let html_header = http::HeaderValue::from_str(\"text/html\")\n .expect(\"static header must be valid\");","typeGuard":null,"tryCatchPattern":"match Response::builder()\n .header(header::CONTENT_TYPE, \"text/html\")\n .status(StatusCode::OK)\n .body(Body::from(html_page))\n{\n Ok(resp) => resp,\n Err(e) => {\n eprintln!(\"error page build failed: {}\", e);\n StatusCode::INTERNAL_SERVER_ERROR.into_response()\n }\n}","preventionTips":["Build error pages with infallible Response::new + headers_mut()","Validate any dynamic header (e.g. CSP) with HeaderValue::from_str before use","Unit-test error_injection_middleware with a build-error response"],"tags":["rust","axum","http","panic","middleware"],"backgroundTag":"http-response-build-failure","analyzedSha":"61d30828217957120309db657950224edf9707e2","analyzedAt":"2026-09-03T14:39:09.727Z","contentChangedAt":"2026-09-03T14:39:09.727Z","schemaVersion":2},"datasetVersion":"2026-09-10T17:17:09.494Z"}