| // Licensed to the Apache Software Foundation (ASF) under one or more |
| // contributor license agreements. See the NOTICE file distributed with |
| // this work for additional information regarding copyright ownership. |
| // The ASF licenses this file to You under the Apache License, Version 2.0 |
| // (the "License"); you may not use this file except in compliance with |
| // the License. You may obtain a copy of the License at |
| // |
| // http://www.apache.org/licenses/LICENSE-2.0 |
| // |
| // Unless required by applicable law or agreed to in writing, software |
| // distributed under the License is distributed on an "AS IS" BASIS, |
| // WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied. |
| // See the License for the specific language governing permissions and |
| // limitations under the License. |
| |
| // starcgen is a tool to generate specialized type assertion shims to be |
| // used in Apache Beam Go SDK pipelines instead of the default reflection shim. |
| // This is done through static analysis of go sources for the package in question. |
| // |
| // The generated type assertion shims have much better performance than the default |
| // reflection based shims used by beam. Reflection is convenient for development, |
| // but is an unnecessary expense on pipeline performance. |
| // |
| // Using This Tool |
| // |
| // This tool is intended for use with `go generate`. The recommended convention |
| // putting the types and functions used in a separate package from pipeline construction. |
| // Then, the tool can be used as follows: |
| // |
| // //go:generate go install github.com/apache/beam/sdks/go/cmd/starcgen |
| // //go:generate starcgen --package=<mypackagename> |
| // //go:generate go fmt |
| // |
| // This will generate registrations and shim types for all types and functions |
| // in the package, in a file `<mypackagename>.shims.go`. |
| // |
| // Alternatively, it's possible to specify the specific input files and identifiers within |
| // the package for generation. |
| // |
| // //go:generate go install github.com/apache/beam/sdks/go/cmd/starcgen |
| // //go:generate starcgen --package=<mypackagename> --inputs=foo.go --identifiers=myFn,myStructFn --output=custom.shims.go |
| // //go:generate go fmt |
| // |
| package main |
| |
| import ( |
| "flag" |
| "fmt" |
| "go/ast" |
| "go/importer" |
| "go/parser" |
| "go/token" |
| "io" |
| "log" |
| "os" |
| "path/filepath" |
| "strings" |
| |
| "github.com/apache/beam/sdks/go/pkg/beam/util/starcgenx" |
| ) |
| |
| var ( |
| inputs = flag.String("inputs", "", "comma separated list of file with types for which to create shims") |
| intendedPkg = flag.String("package", "", "a filter on input go files. Required if inputs unset.") |
| output = flag.String("output", "", "output file with types to create") |
| ids = flag.String("identifiers", "", "comma separated list of package local identifiers for which to generate code") |
| debug = flag.Bool("debug", false, "print out a debugging header in the shim file to help diagnose errors") |
| ) |
| |
| // Generate takes the typechecked inputs, and generates the shim file for the relevant |
| // identifiers. |
| func Generate(w io.Writer, filename, pkg string, ids []string, fset *token.FileSet, files []*ast.File) error { |
| e := starcgenx.NewExtractor(pkg) |
| e.Ids = ids |
| e.Debug = *debug |
| |
| // Importing from source should work in most cases. |
| imp := importer.For("source", nil) |
| if err := e.FromAsts(imp, fset, files); err != nil { |
| // Always print out the debugging info to the file. |
| if _, errw := w.Write(e.Bytes()); errw != nil { |
| return fmt.Errorf("error writing debug data to file after err %v:%v", err, errw) |
| } |
| err = fmt.Errorf("error extracting from asts: %v", err) |
| e.Printf("%v", err) |
| return err |
| } |
| data := e.Generate(filename) |
| if err := write(w, []byte(license)); err != nil { |
| return err |
| } |
| return write(w, data) |
| } |
| |
| func write(w io.Writer, data []byte) error { |
| n, err := w.Write(data) |
| if err != nil && n < len(data) { |
| return fmt.Errorf("short write of data got %d, want %d", n, len(data)) |
| } |
| return err |
| } |
| |
| func usage() { |
| fmt.Fprintf(os.Stderr, "Usage: %v [options] --inputs=<comma separated of go files>\n", filepath.Base(os.Args[0])) |
| flag.PrintDefaults() |
| } |
| |
| func main() { |
| flag.Usage = usage |
| flag.Parse() |
| |
| log.SetFlags(log.Lshortfile) |
| log.SetPrefix("starcgen: ") |
| |
| dir, err := filepath.Abs(filepath.Dir(os.Args[0])) |
| if err != nil { |
| log.Fatal(err) |
| } |
| |
| var ipts []string |
| // If inputs are empty, parse all go files in the local directory. |
| if len(*inputs) == 0 { |
| if *intendedPkg == "" { |
| log.Fatal("--package flag is required to be set when --inputs unset") |
| } |
| globbed, err := filepath.Glob(filepath.Join(dir, "*.go")) |
| if err != nil { |
| log.Fatal(err) |
| } |
| ipts = globbed |
| } else { |
| ipts = strings.Split(*inputs, ",") |
| } |
| |
| // Get an output file for pre-processing if necessary. |
| if *output == "" && *intendedPkg != "" { |
| *output = *intendedPkg + ".shims.go" |
| } |
| |
| outputBase := filepath.Base(*output) |
| |
| fset := token.NewFileSet() |
| var fs []*ast.File |
| pkg := *intendedPkg |
| for _, i := range ipts { |
| // Ignore the existing shim file when re-generating. |
| if strings.HasSuffix(i, outputBase) { |
| continue |
| } |
| |
| f, err := parser.ParseFile(fset, i, nil, 0) |
| if err != nil { |
| log.Fatal(err) // parse error |
| } |
| if pkg == "" { |
| pkg = f.Name.Name |
| } else if pkg != f.Name.Name { |
| // If we've set an intended package, just filter files outside that package. |
| // eg. for pkg_tests in the same directory. |
| if *intendedPkg != "" { |
| continue |
| } |
| log.Fatalf("Input file %v has mismatched package path, got %q, want %q", i, f.Name.Name, pkg) |
| } |
| fs = append(fs, f) |
| } |
| if pkg == "" { |
| log.Fatalf("No package detected in input files: %v", inputs) |
| } |
| |
| f, err := os.OpenFile(*output, os.O_WRONLY|os.O_CREATE|os.O_TRUNC, 0644) |
| if err != nil { |
| log.Fatalf("error opening %q: %v", *output, err) |
| } |
| if err := Generate(f, *output, pkg, strings.Split(*ids, ","), fset, fs); err != nil { |
| log.Fatal(err) |
| } |
| } |
| |
| const license = `// Licensed to the Apache Software Foundation (ASF) under one or more |
| // contributor license agreements. See the NOTICE file distributed with |
| // this work for additional information regarding copyright ownership. |
| // The ASF licenses this file to You under the Apache License, Version 2.0 |
| // (the "License"); you may not use this file except in compliance with |
| // the License. You may obtain a copy of the License at |
| // |
| // http://www.apache.org/licenses/LICENSE-2.0 |
| // |
| // Unless required by applicable law or agreed to in writing, software |
| // distributed under the License is distributed on an "AS IS" BASIS, |
| // WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied. |
| // See the License for the specific language governing permissions and |
| // limitations under the License. |
| |
| ` |