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template.go
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template.go
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// Copyright (c) 2021 Uber Technologies, Inc.
//
// Permission is hereby granted, free of charge, to any person obtaining a copy
// of this software and associated documentation files (the "Software"), to deal
// in the Software without restriction, including without limitation the rights
// to use, copy, modify, merge, publish, distribute, sublicense, and/or sell
// copies of the Software, and to permit persons to whom the Software is
// furnished to do so, subject to the following conditions:
//
// The above copyright notice and this permission notice shall be included in
// all copies or substantial portions of the Software.
//
// THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
// IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
// FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
// AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
// LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
// OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN
// THE SOFTWARE.
package codegen
import (
"bytes"
"io"
"os"
"path/filepath"
"strings"
tmpl "text/template"
"github.com/pkg/errors"
templates "github.com/uber/zanzibar/codegen/template_bundle"
)
// AssetProvider provides access to template assets
type AssetProvider interface {
// AssetNames returns a list of named assets available
AssetNames() []string
// Asset returns the bytes for a provided asset name
Asset(string) ([]byte, error)
}
type defaultAssetCollection struct{}
func (*defaultAssetCollection) AssetNames() []string {
return templates.AssetNames()
}
func (*defaultAssetCollection) Asset(assetName string) ([]byte, error) {
return templates.Asset(assetName)
}
var defaultFuncMap = tmpl.FuncMap{
"lower": strings.ToLower,
"title": strings.Title,
"fullTypeName": fullTypeName,
"camel": CamelCase,
"split": strings.Split,
"dec": decrement,
"basePath": filepath.Base,
"pascal": PascalCase,
"isPointerType": IsPointerType,
"unref": Unref,
"lintAcronym": LintAcronym,
"args": args,
"firstIsClientOrEmpty": firstIsClientOrEmpty,
}
func fullTypeName(typeName, packageName string) string {
if typeName == "" || strings.Contains(typeName, ".") {
return typeName
}
return packageName + "." + typeName
}
// work around since text/template variables can not be overwritten until go1.11
func firstIsClientOrEmpty(list []string) string {
if len(list) > 0 && list[0] == "client" {
return "client"
}
return ""
}
func decrement(num int) int {
return num - 1
}
// IsPointerType determines if the passed in string is a string for a pointer
func IsPointerType(t string) bool {
return strings.HasPrefix(t, "*")
}
// Unref unrefs a pointer reference
func Unref(t string) string {
if strings.HasPrefix(t, "*") {
return strings.TrimLeft(t, "*")
}
return t
}
func args(v ...interface{}) []interface{} {
return v
}
// Template generates code for edge gateway clients and edgegateway endpoints.
type Template struct {
template *tmpl.Template
}
// NewDefaultTemplate creates a bundle of templates.
func NewDefaultTemplate() (*Template, error) {
return NewTemplate(
&defaultAssetCollection{},
defaultFuncMap,
)
}
// NewTemplate returns a template helper for the provided asset collection
func NewTemplate(
assetProvider AssetProvider,
functionMap tmpl.FuncMap,
) (*Template, error) {
t := tmpl.New("main").Funcs(functionMap)
for _, file := range assetProvider.AssetNames() {
fileContent, err := assetProvider.Asset(file)
if err != nil {
return nil, errors.Wrapf(
err,
"Could not read bin data for template %s",
file,
)
}
if _, err := t.New(file).Parse(string(fileContent)); err != nil {
return nil, errors.Wrapf(err, "Could not parse template %s", file)
}
}
return &Template{
template: t,
}, nil
}
// ExecTemplate executes the named templated, returning the generated bytes
func (t *Template) ExecTemplate(
tplName string,
tplData interface{},
pkgHelper *PackageHelper,
buildTags ...string,
) (ret []byte, rErr error) {
defer func() {
if r := recover(); r != nil {
rErr = errors.Errorf(
"panic when generating %s template in %s: %+v",
tplName, pkgHelper.packageRoot, r,
)
}
}()
tplBuffer := bytes.NewBuffer(nil)
if _, err := io.WriteString(tplBuffer, "// Code generated by zanzibar \n"+
"// @generated \n \n"); err != nil {
rErr = errors.Wrapf(err, "failed to write to file: %s", err)
return
}
buildTagsLine := strings.Join(buildTags, " ")
if buildTagsLine != "" {
if _, err := io.WriteString(tplBuffer, "// +build "+buildTagsLine+"\n\n"); err != nil {
rErr = errors.Wrapf(err, "failed to write to file: %s", err)
return
}
}
if _, err := io.WriteString(tplBuffer, pkgHelper.copyrightHeader); err != nil {
rErr = errors.Wrapf(err, "failed to write to file: %s", err)
return
}
if _, err := io.WriteString(tplBuffer, "\n\n"); err != nil {
rErr = errors.Wrapf(err, "failed to write to file: %s", err)
return
}
if err := t.template.ExecuteTemplate(
tplBuffer,
tplName,
tplData,
); err != nil {
rErr = errors.Wrapf(
err,
"Error generating template %s",
tplName,
)
}
ret = tplBuffer.Bytes()
return
}
func openFileOrCreate(file string) (*os.File, error) {
if _, err := os.Stat(file); os.IsNotExist(err) {
if err := os.MkdirAll(filepath.Dir(file), os.ModePerm); err != nil {
return nil, errors.Wrapf(
err, "could not make directory: %s", file,
)
}
}
return os.OpenFile(file, os.O_CREATE|os.O_TRUNC|os.O_WRONLY, 0644)
}