{"record":{"id":"4613b5a5388fe080","repo":"apache/beam","slug":"error-extracting-from-asts-v","errorCode":null,"errorMessage":"error extracting from asts: %v","messagePattern":"error extracting from asts: (.+?)","errorType":"exception","errorClass":null,"httpStatus":null,"severity":"error","filePath":"sdks/go/cmd/starcgen/starcgen.go","lineNumber":83,"sourceCode":"\tids         = flag.String(\"identifiers\", \"\", \"comma separated list of package local identifiers for which to generate code\")\n\tdebug       = flag.Bool(\"debug\", false, \"print out a debugging header in the shim file to help diagnose errors\")\n)\n\n// Generate takes the typechecked inputs, and generates the shim file for the relevant\n// identifiers.\nfunc Generate(w io.Writer, filename, pkg string, ids []string, fset *token.FileSet, files []*ast.File) error {\n\te := starcgenx.NewExtractor(pkg)\n\te.Ids = ids\n\te.Debug = *debug\n\n\t// Importing from source should work in most cases.\n\timp := importer.For(\"source\", nil)\n\tif err := e.FromAsts(imp, fset, files); err != nil {\n\t\t// Always print out the debugging info to the file.\n\t\tif _, errw := w.Write(e.Bytes()); errw != nil {\n\t\t\treturn fmt.Errorf(\"error writing debug data to file after err %v:%v\", err, errw)\n\t\t}\n\t\terr = fmt.Errorf(\"error extracting from asts: %v\", err)\n\t\te.Printf(\"%v\", err)\n\t\treturn err\n\t}\n\tdata := e.Generate(filename)\n\tif err := write(w, []byte(license)); err != nil {\n\t\treturn err\n\t}\n\treturn write(w, data)\n}\n\nfunc write(w io.Writer, data []byte) error {\n\tn, err := w.Write(data)\n\tif err != nil && n < len(data) {\n\t\treturn fmt.Errorf(\"short write of data got %d, want %d\", n, len(data))\n\t}\n\treturn err\n}\n","sourceCodeStart":65,"sourceCodeEnd":101,"githubUrl":"https://github.com/apache/beam/blob/12126d8942aaf848030c478b4c6a28c6af861c66/sdks/go/cmd/starcgen/starcgen.go#L65-L101","documentation":"starcgen.Generate wraps any error returned by e.FromAsts (the extraction step that converts parsed Go ASTs into the generator's intermediate representation) as 'error extracting from asts: %v'. starcgen generates Beam schema encoders/decoders from Go source files, and this error means the source could not be analyzed for type information.","triggerScenarios":"Running starcgen with --inputs pointing at Go files that fail type-checking: undefined types/packages, import errors, syntax-adjacent issues, or types outside the 'source' importer's reach.","commonSituations":"Generating from files that don't compile (missing dependencies in the module), referencing external packages not resolvable by importer.For(\"source\"), or running starcgen on files with generics/types unsupported by the extractor.","solutions":["Read the wrapped cause: fix the underlying compile/type error in the input Go files first.","Run `go build ./...` on the package being generated to confirm it compiles standalone.","Ensure all imported packages are present in the module (go mod tidy).","Check the debug output file written by Generate for the exact failing type/AST node.","If a specific type construct is unsupported, simplify it or upgrade the Beam SDK."],"exampleFix":"// before (input references undefined type)\ntype Row struct { X UnknownType }\n// after\ntype Row struct { X string } // ensure the referenced package is imported and exists","handlingStrategy":"validation","validationCode":"if err := exec.Command(\"go\", \"build\", \"./...\").Run(); err != nil { return fmt.Errorf(\"package must compile before starcgen: %w\", err) }","typeGuard":null,"tryCatchPattern":"err := gen.Generate(w, ...)\nif err != nil && strings.Contains(err.Error(), \"error extracting from asts\") {\n\tlog.Fatalf(\"fix source type errors: %v\", err)\n}","preventionTips":["Run `go build ./...` (or `go vet`) on input packages before generation.","Run `go mod tidy` so all imported packages resolve.","Keep generated-source inputs simple; avoid constructs unsupported by the extractor."],"tags":["go","code-generation","ast","type-checking"],"backgroundTag":"schema-validation-failed","analyzedSha":"12126d8942aaf848030c478b4c6a28c6af861c66","analyzedAt":"2026-09-13T01:50:10.254Z","contentChangedAt":"2026-09-13T01:50:10.254Z","schemaVersion":2},"datasetVersion":"2026-09-20T03:17:13.778Z"}