1 /* 2 Copyright 2020 Google LLC 3 4 Licensed under the Apache License, Version 2.0 (the "License"); 5 you may not use this file except in compliance with the License. 6 You may obtain a copy of the License at 7 8 https://www.apache.org/licenses/LICENSE-2.0 9 10 Unless required by applicable law or agreed to in writing, software 11 distributed under the License is distributed on an "AS IS" BASIS, 12 WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied. 13 See the License for the specific language governing permissions and 14 limitations under the License. 15 */ 16 17 package warn 18 19 import ( 20 "github.com/bazelbuild/buildtools/build" 21 ) 22 23 // FileReader is a class that can read an arbitrary Starlark file 24 // from the repository and cache the results. 25 type FileReader struct { 26 cache map[string]*build.File 27 readFile func(string) ([]byte, error) 28 } 29 30 // NewFileReader creates and initializes a FileReader instance with a 31 // custom readFile function that can read an arbitrary file in the 32 // repository using a path relative to the workspace root 33 // (OS-independent, with forward slashes). 34 func NewFileReader(readFile func(string) ([]byte, error)) *FileReader { 35 return &FileReader{ 36 cache: make(map[string]*build.File), 37 readFile: readFile, 38 } 39 } 40 41 // retrieveFile reads a Starlark file using only the readFile method 42 // (without using the cache). 43 func (fr *FileReader) retrieveFile(filename string) *build.File { 44 contents, err := fr.readFile(filename) 45 if err != nil { 46 return nil 47 } 48 49 file, err := build.Parse(filename, contents) 50 if err != nil { 51 return nil 52 } 53 file.Path = filename 54 55 return file 56 } 57 58 // GetFile reads a Starlark file from the repository or the cache. 59 // Returns nil if the file is not found or not valid. 60 func (fr *FileReader) GetFile(pkg, label string) *build.File { 61 filename := label 62 if pkg != "" { 63 filename = pkg + "/" + label 64 } 65 66 // Try to retrieve from the cache 67 if file, ok := fr.cache[filename]; ok { 68 return file 69 } 70 file := fr.retrieveFile(filename) 71 if file != nil { 72 file.Pkg = pkg 73 file.Label = label 74 } 75 fr.cache[filename] = file 76 return file 77 } 78