package funcs
import (
"encoding/base64"
"fmt"
"io/ioutil"
"os"
"path/filepath"
"unicode/utf8"
"github.com/hashicorp/hcl2/hcl"
"github.com/hashicorp/hcl2/hcl/hclsyntax"
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()
src, err := readFileBytes(baseDir, path)
if err != nil {
return cty.UnknownVal(cty.String), err
}
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; use the filebase64 function to obtain the Base64 encoded contents or the other file functions (e.g. filemd5, filesha256) to obtain file hashing results instead", path)
}
return cty.StringVal(string(src)), nil
}
},
})
}
// MakeTemplateFileFunc constructs a function that takes a file path and
// an arbitrary object of named values and attempts to render the referenced
// file as a template using HCL template syntax.
//
// The template itself may recursively call other functions so a callback
// must be provided to get access to those functions. The template cannot,
// however, access any variables defined in the scope: it is restricted only to
// those variables provided in the second function argument, to ensure that all
// dependencies on other graph nodes can be seen before executing this function.
//
// As a special exception, a referenced template file may not recursively call
// the templatefile function, since that would risk the same file being
// included into itself indefinitely.
func MakeTemplateFileFunc(baseDir string, funcsCb func() map[string]function.Function) function.Function {
params := []function.Parameter{
{
Name: "path",
Type: cty.String,
},
{
Name: "vars",
Type: cty.DynamicPseudoType,
},
}
loadTmpl := func(fn string) (hcl.Expression, error) {
// We re-use File here to ensure the same filename interpretation
// as it does, along with its other safety checks.
tmplVal, err := File(baseDir, cty.StringVal(fn))
if err != nil {
return nil, err
}
expr, diags := hclsyntax.ParseTemplate([]byte(tmplVal.AsString()), fn, hcl.Pos{Line: 1, Column: 1})
if diags.HasErrors() {
return nil, diags
}
return expr, nil
}
renderTmpl := func(expr hcl.Expression, varsVal cty.Value) (cty.Value, error) {
if varsTy := varsVal.Type(); !(varsTy.IsMapType() || varsTy.IsObjectType()) {
return cty.DynamicVal, function.NewArgErrorf(1, "invalid vars value: must be a map") // or an object, but we don't strongly distinguish these most of the time
}
ctx := &hcl.EvalContext{
Variables: varsVal.AsValueMap(),
}
// We'll pre-check references in the template here so we can give a
// more specialized error message than HCL would by default, so it's
// clearer that this problem is coming from a templatefile call.
for _, traversal := range expr.Variables() {
root := traversal.RootName()
if _, ok := ctx.Variables[root]; !ok {
return cty.DynamicVal, function.NewArgErrorf(1, "vars map does not contain key %q, referenced at %s", root, traversal[0].SourceRange())
}
}
givenFuncs := funcsCb() // this callback indirection is to avoid chicken/egg problems
funcs := make(map[string]function.Function, len(givenFuncs))
for name, fn := range givenFuncs {
if name == "templatefile" {
// We stub this one out to prevent recursive calls.
funcs[name] = function.New(&function.Spec{
Params: params,
Type: func(args []cty.Value) (cty.Type, error) {
return cty.NilType, fmt.Errorf("cannot recursively call templatefile from inside templatefile call")
},
})
continue
}
funcs[name] = fn
}
ctx.Functions = funcs
val, diags := expr.Value(ctx)
if diags.HasErrors() {
return cty.DynamicVal, diags
}
return val, nil
}
return function.New(&function.Spec{
Params: params,
Type: func(args []cty.Value) (cty.Type, error) {
if !(args[0].IsKnown() && args[1].IsKnown()) {
return cty.DynamicPseudoType, nil
}
// We'll render our template now to see what result type it produces.
// A template consisting only of a single interpolation an potentially
// return any type.
expr, err := loadTmpl(args[0].AsString())
if err != nil {
return cty.DynamicPseudoType, err
}
// This is safe even if args[1] contains unknowns because the HCL
// template renderer itself knows how to short-circuit those.
val, err := renderTmpl(expr, args[1])
return val.Type(), err
},
Impl: func(args []cty.Value, retType cty.Type) (cty.Value, error) {
expr, err := loadTmpl(args[0].AsString())
if err != nil {
return cty.DynamicVal, err
}
return renderTmpl(expr, args[1])
},
})
}
// 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())
},
})
}
// BasenameFunc constructs a function that takes a string containing a filesystem path
// and removes all except the last portion from it.
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
},
})
// DirnameFunc constructs a function that takes a string containing a filesystem path
// and removes the last portion from it.
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
},
})
// AbsPathFunc constructs a function that converts a filesystem path to an absolute path
var AbsPathFunc = 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) {
absPath, err := filepath.Abs(args[0].AsString())
return cty.StringVal(filepath.ToSlash(absPath)), err
},
})
// 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
},
})
func readFileBytes(baseDir, path string) ([]byte, error) {
path, err := homedir.Expand(path)
if err != nil {
return nil, 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 nil, fmt.Errorf("no file exists at %s", path)
}
return nil, fmt.Errorf("failed to read %s", path)
}
return src, nil
}
// 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})
}
// 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})
}
// 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})
}
// 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})
}
// 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})
}
