wdcli: Update handling of templates
This commit updates the handling of expanding of templates. This is to prepare embeding templates directly as opposed to embedding a single resource directory.
This commit is contained in:
Tom Wiesing
parent
2881a5f65c
commit
e75dc29de1
6 changed files with 234 additions and 111 deletions
1
embed/paths.go
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1
embed/paths.go
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@ -0,0 +1 @@
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package embed
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@ -1,110 +0,0 @@
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package embed
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import (
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"io"
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"io/fs"
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"os"
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"regexp"
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"strings"
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"github.com/pkg/errors"
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"golang.org/x/exp/maps"
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"golang.org/x/exp/slices"
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)
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var templateRegexp = regexp.MustCompile(`\${[^}]+}`)
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// InstallTemplates open the resource src, and installs it into dst.
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// the template resource must fit into memory.
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//
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// For each variable ${THING} inside dest, a key 'THING' must exist in context.
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// Extra or missing template keys are an error.
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func InstallTemplate(dst, src string, context map[string]string) error {
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bytes, srcMode, err := doTemplate(src, context)
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if err != nil {
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return err
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}
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// determine if we need to create the destination file, or if it already exists
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dstStat, dstErr := os.Stat(dst)
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switch {
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case os.IsNotExist(dstErr):
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case dstErr != nil:
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return errors.Wrapf(dstErr, "Error calling stat on destination %s", dst)
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case dstStat.IsDir():
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return errors.Wrapf(errExpectedFileButGotDirectory, "Error processing destination %s", dst)
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}
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// open and write the destination file
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dstFile, err := os.OpenFile(dst, os.O_WRONLY|os.O_CREATE|os.O_TRUNC, srcMode)
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if err != nil {
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return errors.Wrapf(err, "Unable to open file %s", dst)
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}
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_, err = dstFile.Write(bytes)
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return errors.Wrapf(err, "Unable to write destination %s", dst)
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}
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// ReadTemplate is like InstallTemplate, except that it writes template into a byte slice and returns it.
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func ReadTemplate(src string, context map[string]string) ([]byte, error) {
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bytes, _, err := doTemplate(src, context)
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return bytes, err
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}
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func doTemplate(src string, context map[string]string) (bytes []byte, mode fs.FileMode, err error) {
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// open the source file!
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srcFile, err := resourceEmbed.Open(src)
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if err != nil {
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return nil, mode, errors.Wrapf(err, "Error opening source file %s", src)
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}
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defer srcFile.Close()
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// stat the source file to install
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srcStat, srcErr := srcFile.Stat()
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if srcErr != nil {
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return nil, mode, errors.Wrapf(srcErr, "Error calling stat on source %s", src)
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}
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// should not be a directory
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if srcStat.IsDir() {
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return nil, mode, errors.Wrapf(errExpectedFileButGotDirectory, "Error calling stat on source %s", src)
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}
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// read the template and replace
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templates, err := io.ReadAll(srcFile)
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if err != nil {
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return nil, mode, errors.Wrapf(err, "Unable to read src file %s", src)
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}
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// keep track of context keys that have not been used
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unuusedContext := make(map[string]struct{}, len(context))
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for key := range context {
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unuusedContext[key] = struct{}{}
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}
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// replace the template regexp
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// keeping track of unuused errors
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var hadError error
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templates = templateRegexp.ReplaceAllFunc(templates, func(b []byte) []byte {
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name := string(b[2 : len(b)-1]) // remove the leading ${ and trailing }
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delete(unuusedContext, name) // mark the key as having been read
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value, ok := context[name]
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if hadError != nil && !ok {
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hadError = errors.Errorf("key %s missing in context", name)
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}
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return []byte(value)
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})
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if hadError != nil {
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return nil, mode, hadError
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}
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if len(unuusedContext) != 0 {
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keys := maps.Keys(unuusedContext)
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slices.Sort(keys)
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return nil, mode, errors.Errorf("additional keys %s in context", strings.Join(keys, ","))
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}
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// return the data and the mode!
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return templates, srcStat.Mode(), nil
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}
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60
embed/template.go
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60
embed/template.go
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@ -0,0 +1,60 @@
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package embed
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import (
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"os"
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"github.com/FAU-CDI/wisski-distillery/internal/unpack"
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"github.com/pkg/errors"
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)
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// InstallTemplates open the resource src, and installs it into dst.
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// the template resource must fit into memory.
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//
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// For each variable ${THING} inside dest, a key 'THING' must exist in context.
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// Extra or missing template keys are an error.
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func InstallTemplate(dst, src string, context map[string]string) error {
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// open the source file!
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srcFile, err := resourceEmbed.Open(src)
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if err != nil {
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return errors.Wrapf(err, "Error opening source file %s", src)
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}
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defer srcFile.Close()
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// write the template
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bytes, srcMode, err := unpack.UnpackTemplate(context, srcFile)
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if err != nil {
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return err
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}
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// determine if we need to create the destination file, or if it already exists
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dstStat, dstErr := os.Stat(dst)
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switch {
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case os.IsNotExist(dstErr):
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case dstErr != nil:
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return errors.Wrapf(dstErr, "Error calling stat on destination %s", dst)
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case dstStat.IsDir():
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return errors.Wrapf(errExpectedFileButGotDirectory, "Error processing destination %s", dst)
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}
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// open and write the destination file
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dstFile, err := os.OpenFile(dst, os.O_WRONLY|os.O_CREATE|os.O_TRUNC, srcMode)
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if err != nil {
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return errors.Wrapf(err, "Unable to open file %s", dst)
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}
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_, err = dstFile.Write(bytes)
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return errors.Wrapf(err, "Unable to write destination %s", dst)
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}
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// ReadTemplate is like InstallTemplate, except that it writes template into a byte slice and returns it.
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func ReadTemplate(src string, context map[string]string) ([]byte, error) {
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// open the source file!
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srcFile, err := resourceEmbed.Open(src)
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if err != nil {
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return nil, errors.Wrapf(err, "Error opening source file %s", src)
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}
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defer srcFile.Close()
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// and return it
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bytes, _, err := unpack.UnpackTemplate(context, srcFile)
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return bytes, err
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}
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2
go.mod
2
go.mod
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@ -3,6 +3,7 @@ module github.com/FAU-CDI/wisski-distillery
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go 1.18
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require (
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github.com/FAU-CDI/wdresolve v0.0.0-20220909150742-34bde844301d
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github.com/Showmax/go-fqdn v1.0.0
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github.com/alessio/shellescape v1.4.1
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github.com/feiin/sqlstring v0.3.0
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@ -14,7 +15,6 @@ require (
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)
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require (
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github.com/FAU-CDI/wdresolve v0.0.0-20220909150742-34bde844301d // indirect
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github.com/go-sql-driver/mysql v1.6.0 // indirect
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github.com/jessevdk/go-flags v1.5.0 // indirect
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github.com/jinzhu/inflection v1.0.0 // indirect
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172
internal/unpack/template.go
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172
internal/unpack/template.go
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@ -0,0 +1,172 @@
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// Package unpack unpacks files and templates to a target directory.
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package unpack
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import (
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"bufio"
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"bytes"
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"io"
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"io/fs"
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"strings"
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"github.com/pkg/errors"
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"golang.org/x/exp/maps"
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"golang.org/x/exp/slices"
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)
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var errExpectedFileButGotDirectory = errors.New("Expected a file, but got a directory")
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// UnpackTemplate unpacks the given file template and template
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func UnpackTemplate(context map[string]string, src fs.File) ([]byte, fs.FileMode, error) {
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// stat the source file to install
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srcStat, srcErr := src.Stat()
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if srcErr != nil {
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return nil, 0, errors.Wrapf(srcErr, "Error calling stat on source")
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}
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// should not be a directory
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if srcStat.IsDir() {
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return nil, 0, errors.Wrapf(errExpectedFileButGotDirectory, "Error calling stat on source %s", srcStat.Name())
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}
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// read all the bytes into a buffer
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var buffer bytes.Buffer
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WriteTemplate(&buffer, context, src)
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return buffer.Bytes(), srcStat.Mode(), nil
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}
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type templateMode int
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const (
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templateModeNormal templateMode = iota // normal mode
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templateModeDollar // saw '$'
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templateModeOpen // saw '${'
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)
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// WriteTemplate writes the template defined by src with the given context into reader.
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//
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// To run the template, variables of the form ${NAME} are replaced with their corresponding value from the context.
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//
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// Extra or missing variables from the context are an error.
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func WriteTemplate(dst io.Writer, context map[string]string, src io.Reader) error {
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// keep track of context keys that have not been used
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unuusedContext := make(map[string]struct{}, len(context))
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for key := range context {
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unuusedContext[key] = struct{}{}
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}
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reader := bufio.NewReader(src) // a new reader
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var missingKeyErr error // error for missing keys
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var builder strings.Builder // holding variable names
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mode := templateModeNormal // the current mode of the reader
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parseloop:
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for {
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r, _, err := reader.ReadRune()
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switch {
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case err == io.EOF:
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/* finished the source, see below */
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break parseloop
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case err != nil:
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/* something went wrong */
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return err
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case mode == templateModeNormal && r == '$':
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// saw a '$' in normal mode
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// => switch to the dollar mode
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mode = templateModeDollar
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case mode == templateModeNormal:
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// saw anything else
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// => just pass it through
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if _, err := dst.Write([]byte{byte(r)}); err != nil {
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return err
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}
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case mode == templateModeDollar && r == '{':
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// saw '{', following the '$'
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// => read everything else into the buffer
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mode = templateModeOpen
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case mode == templateModeDollar && r == '$':
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// saw a '$' following the '$'
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// => write the first '$', and handle the case $${stuff}
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if _, err := dst.Write([]byte("$")); err != nil {
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return err
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}
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case mode == templateModeDollar:
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// saw anything else following the '$'
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// => write both back and switch back to normal mode
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if _, err := dst.Write([]byte{byte('$'), byte(r)}); err != nil {
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return err
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}
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mode = templateModeNormal
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case mode == templateModeOpen && r != '}':
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// saw anything except for closing bracket
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// => keep it in the buffer
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if _, err := builder.WriteRune(r); err != nil {
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return err
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}
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case mode == templateModeOpen:
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// saw a closing '}' inside the open mode
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// => use the variable
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name := builder.String()
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delete(unuusedContext, name) // mark the variable as used
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// get the variable from the context
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value, ok := context[name]
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if missingKeyErr != nil && !ok {
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missingKeyErr = errors.Errorf("key %s missing in context", name)
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}
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// write the replacement into the string
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if _, err := io.WriteString(dst, value); err != nil {
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return err
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}
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// reset the builder and go back into normal mode
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builder.Reset()
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mode = templateModeNormal
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default:
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panic("never reached")
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}
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}
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// cleanup at end of input
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switch mode {
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case templateModeNormal:
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// => everything is fine
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case templateModeDollar:
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// we had a '$', but no '{'
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// => write the trailing '$' into dest
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if _, err := dst.Write([]byte("$")); err != nil {
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return err
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}
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case templateModeOpen:
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// we had a "${", followed by somthing unclosed
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// => write everything back into the dst
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if _, err := dst.Write([]byte("${")); err != nil {
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return err
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}
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if _, err := io.WriteString(dst, builder.String()); err != nil {
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return err
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}
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default:
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panic("never reached")
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}
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// check if there was a missing key!
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if missingKeyErr != nil {
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return missingKeyErr
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}
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// check if there was an unused key!
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if len(unuusedContext) != 0 {
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keys := maps.Keys(unuusedContext)
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slices.Sort(keys)
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return errors.Errorf("additional keys %s in context", strings.Join(keys, ","))
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}
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return nil
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}
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