terraform/lang/funcs/filesystem.go

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package funcs
import (
"encoding/base64"
"fmt"
"io/ioutil"
"os"
"path/filepath"
"unicode/utf8"
homedir "github.com/mitchellh/go-homedir"
"github.com/zclconf/go-cty/cty"
"github.com/zclconf/go-cty/cty/function"
)
// MakeFileFunc constructs a function that takes a file path and returns the
// contents of that file, either directly as a string (where valid UTF-8 is
// required) or as a string containing base64 bytes.
func MakeFileFunc(baseDir string, encBase64 bool) function.Function {
return function.New(&function.Spec{
Params: []function.Parameter{
{
Name: "path",
Type: cty.String,
},
},
Type: function.StaticReturnType(cty.String),
Impl: func(args []cty.Value, retType cty.Type) (cty.Value, error) {
path := args[0].AsString()
path, err := homedir.Expand(path)
if err != nil {
return cty.UnknownVal(cty.String), fmt.Errorf("failed to expand ~: %s", err)
}
if !filepath.IsAbs(path) {
path = filepath.Join(baseDir, path)
}
// Ensure that the path is canonical for the host OS
path = filepath.Clean(path)
src, err := ioutil.ReadFile(path)
if err != nil {
// ReadFile does not return Terraform-user-friendly error
// messages, so we'll provide our own.
if os.IsNotExist(err) {
return cty.UnknownVal(cty.String), fmt.Errorf("no file exists at %s", path)
}
return cty.UnknownVal(cty.String), fmt.Errorf("failed to read %s", path)
}
switch {
case encBase64:
enc := base64.StdEncoding.EncodeToString(src)
return cty.StringVal(enc), nil
default:
if !utf8.Valid(src) {
return cty.UnknownVal(cty.String), fmt.Errorf("contents of %s are not valid UTF-8; to read arbitrary bytes, use the filebase64 function instead", path)
}
return cty.StringVal(string(src)), nil
}
},
})
}
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// MakeFileExistsFunc constructs a function that takes a path
// and determines whether a file exists at that path
func MakeFileExistsFunc(baseDir string) function.Function {
return function.New(&function.Spec{
Params: []function.Parameter{
{
Name: "path",
Type: cty.String,
},
},
Type: function.StaticReturnType(cty.Bool),
Impl: func(args []cty.Value, retType cty.Type) (cty.Value, error) {
path := args[0].AsString()
path, err := homedir.Expand(path)
if err != nil {
return cty.UnknownVal(cty.Bool), fmt.Errorf("failed to expand ~: %s", err)
}
if !filepath.IsAbs(path) {
path = filepath.Join(baseDir, path)
}
// Ensure that the path is canonical for the host OS
path = filepath.Clean(path)
fi, err := os.Stat(path)
if err != nil {
if os.IsNotExist(err) {
return cty.False, nil
}
return cty.UnknownVal(cty.Bool), fmt.Errorf("failed to stat %s", path)
}
if fi.Mode().IsRegular() {
return cty.True, nil
}
return cty.False, fmt.Errorf("%s is not a regular file, but %q",
path, fi.Mode().String())
},
})
}
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// BasenameFunc constructs a function that takes a string containing a filesystem path
// and removes all except the last portion from it.
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var BasenameFunc = function.New(&function.Spec{
Params: []function.Parameter{
{
Name: "path",
Type: cty.String,
},
},
Type: function.StaticReturnType(cty.String),
Impl: func(args []cty.Value, retType cty.Type) (cty.Value, error) {
return cty.StringVal(filepath.Base(args[0].AsString())), nil
},
})
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// DirnameFunc constructs a function that takes a string containing a filesystem path
// and removes the last portion from it.
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var DirnameFunc = function.New(&function.Spec{
Params: []function.Parameter{
{
Name: "path",
Type: cty.String,
},
},
Type: function.StaticReturnType(cty.String),
Impl: func(args []cty.Value, retType cty.Type) (cty.Value, error) {
return cty.StringVal(filepath.Dir(args[0].AsString())), nil
},
})
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// PathExpandFunc constructs a function that expands a leading ~ character to the current user's home directory.
var PathExpandFunc = function.New(&function.Spec{
Params: []function.Parameter{
{
Name: "path",
Type: cty.String,
},
},
Type: function.StaticReturnType(cty.String),
Impl: func(args []cty.Value, retType cty.Type) (cty.Value, error) {
homePath, err := homedir.Expand(args[0].AsString())
return cty.StringVal(homePath), err
},
})
// File reads the contents of the file at the given path.
//
// The file must contain valid UTF-8 bytes, or this function will return an error.
//
// The underlying function implementation works relative to a particular base
// directory, so this wrapper takes a base directory string and uses it to
// construct the underlying function before calling it.
func File(baseDir string, path cty.Value) (cty.Value, error) {
fn := MakeFileFunc(baseDir, false)
return fn.Call([]cty.Value{path})
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}
// FileExists determines whether a file exists at the given path.
//
// The underlying function implementation works relative to a particular base
// directory, so this wrapper takes a base directory string and uses it to
// construct the underlying function before calling it.
func FileExists(baseDir string, path cty.Value) (cty.Value, error) {
fn := MakeFileExistsFunc(baseDir)
return fn.Call([]cty.Value{path})
}
// FileBase64 reads the contents of the file at the given path.
//
// The bytes from the file are encoded as base64 before returning.
//
// The underlying function implementation works relative to a particular base
// directory, so this wrapper takes a base directory string and uses it to
// construct the underlying function before calling it.
func FileBase64(baseDir string, path cty.Value) (cty.Value, error) {
fn := MakeFileFunc(baseDir, true)
return fn.Call([]cty.Value{path})
}
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// Basename takes a string containing a filesystem path and removes all except the last portion from it.
//
// The underlying function implementation works only with the path string and does not access the filesystem itself.
// It is therefore unable to take into account filesystem features such as symlinks.
//
// If the path is empty then the result is ".", representing the current working directory.
func Basename(path cty.Value) (cty.Value, error) {
return BasenameFunc.Call([]cty.Value{path})
}
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// Dirname takes a string containing a filesystem path and removes the last portion from it.
//
// The underlying function implementation works only with the path string and does not access the filesystem itself.
// It is therefore unable to take into account filesystem features such as symlinks.
//
// If the path is empty then the result is ".", representing the current working directory.
func Dirname(path cty.Value) (cty.Value, error) {
return DirnameFunc.Call([]cty.Value{path})
}
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// Pathexpand takes a string that might begin with a `~` segment, and if so it replaces that segment with
// the current user's home directory path.
//
// The underlying function implementation works only with the path string and does not access the filesystem itself.
// It is therefore unable to take into account filesystem features such as symlinks.
//
// If the leading segment in the path is not `~` then the given path is returned unmodified.
func Pathexpand(path cty.Value) (cty.Value, error) {
return PathExpandFunc.Call([]cty.Value{path})
}