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session.go
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session.go
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// Copyright (c) HashiCorp, Inc.
// SPDX-License-Identifier: MPL-2.0
package repl
import (
"fmt"
"sort"
"strings"
"github.com/zclconf/go-cty/cty"
"github.com/hashicorp/hcl/v2"
"github.com/hashicorp/hcl/v2/hclsyntax"
"github.com/hashicorp/terraform/internal/lang"
"github.com/hashicorp/terraform/internal/lang/marks"
"github.com/hashicorp/terraform/internal/lang/types"
"github.com/hashicorp/terraform/internal/tfdiags"
)
// Session represents the state for a single REPL session.
type Session struct {
// Scope is the evaluation scope where expressions will be evaluated.
Scope *lang.Scope
}
// Handle handles a single line of input from the REPL.
//
// This is a stateful operation if a command is given (such as setting
// a variable). This function should not be called in parallel.
//
// The return value is the output and the error to show.
func (s *Session) Handle(line string) (string, bool, tfdiags.Diagnostics) {
switch {
case strings.TrimSpace(line) == "":
return "", false, nil
case strings.TrimSpace(line) == "exit":
return "", true, nil
case strings.TrimSpace(line) == "help":
ret, diags := s.handleHelp()
return ret, false, diags
default:
ret, diags := s.handleEval(line)
return ret, false, diags
}
}
func (s *Session) handleEval(line string) (string, tfdiags.Diagnostics) {
var diags tfdiags.Diagnostics
// Parse the given line as an expression
expr, parseDiags := hclsyntax.ParseExpression([]byte(line), "<console-input>", hcl.Pos{Line: 1, Column: 1})
diags = diags.Append(parseDiags)
if parseDiags.HasErrors() {
return "", diags
}
val, valDiags := s.Scope.EvalExpr(expr, cty.DynamicPseudoType)
diags = diags.Append(valDiags)
if valDiags.HasErrors() {
return "", diags
}
// The TypeType mark is used only by the console-only `type` function, in
// order to smuggle the type of a given value back here. We can then
// display a representation of the type directly.
if marks.Contains(val, marks.TypeType) {
val, _ = val.UnmarkDeep()
valType := val.Type()
switch {
case valType.Equals(types.TypeType):
// An encapsulated type value, which should be displayed directly.
valType := val.EncapsulatedValue().(*cty.Type)
return typeString(*valType), diags
default:
diags = diags.Append(tfdiags.Sourceless(
tfdiags.Error,
"Invalid use of type function",
"The console-only \"type\" function cannot be used as part of an expression.",
))
return "", diags
}
}
return FormatValue(val, 0), diags
}
func (s *Session) handleHelp() (string, tfdiags.Diagnostics) {
text := `
The Terraform console allows you to experiment with Terraform interpolations.
You may access resources in the state (if you have one) just as you would
from a configuration. For example: "aws_instance.foo.id" would evaluate
to the ID of "aws_instance.foo" if it exists in your state.
Type in the interpolation to test and hit <enter> to see the result.
To exit the console, type "exit" and hit <enter>, or use Control-C or
Control-D.
`
return strings.TrimSpace(text), nil
}
// Modified copy of TypeString from go-cty:
// https://github.com/zclconf/go-cty-debug/blob/master/ctydebug/type_string.go
//
// TypeString returns a string representation of a given type that is
// reminiscent of Go syntax calling into the cty package but is mainly
// intended for easy human inspection of values in tests, debug output, etc.
//
// The resulting string will include newlines and indentation in order to
// increase the readability of complex structures. It always ends with a
// newline, so you can print this result directly to your output.
func typeString(ty cty.Type) string {
var b strings.Builder
writeType(ty, &b, 0)
return b.String()
}
func writeType(ty cty.Type, b *strings.Builder, indent int) {
switch {
case ty == cty.NilType:
b.WriteString("nil")
return
case ty.IsObjectType():
atys := ty.AttributeTypes()
if len(atys) == 0 {
b.WriteString("object({})")
return
}
attrNames := make([]string, 0, len(atys))
for name := range atys {
attrNames = append(attrNames, name)
}
sort.Strings(attrNames)
b.WriteString("object({\n")
indent++
for _, name := range attrNames {
aty := atys[name]
b.WriteString(indentSpaces(indent))
fmt.Fprintf(b, "%s: ", name)
writeType(aty, b, indent)
b.WriteString(",\n")
}
indent--
b.WriteString(indentSpaces(indent))
b.WriteString("})")
case ty.IsTupleType():
etys := ty.TupleElementTypes()
if len(etys) == 0 {
b.WriteString("tuple([])")
return
}
b.WriteString("tuple([\n")
indent++
for _, ety := range etys {
b.WriteString(indentSpaces(indent))
writeType(ety, b, indent)
b.WriteString(",\n")
}
indent--
b.WriteString(indentSpaces(indent))
b.WriteString("])")
case ty.IsCollectionType():
ety := ty.ElementType()
switch {
case ty.IsListType():
b.WriteString("list(")
case ty.IsMapType():
b.WriteString("map(")
case ty.IsSetType():
b.WriteString("set(")
default:
// At the time of writing there are no other collection types,
// but we'll be robust here and just pass through the GoString
// of anything we don't recognize.
b.WriteString(ty.FriendlyName())
return
}
// Because object and tuple types render split over multiple
// lines, a collection type container around them can end up
// being hard to see when scanning, so we'll generate some extra
// indentation to make a collection of structural type more visually
// distinct from the structural type alone.
complexElem := ety.IsObjectType() || ety.IsTupleType()
if complexElem {
indent++
b.WriteString("\n")
b.WriteString(indentSpaces(indent))
}
writeType(ty.ElementType(), b, indent)
if complexElem {
indent--
b.WriteString(",\n")
b.WriteString(indentSpaces(indent))
}
b.WriteString(")")
default:
// For any other type we'll just use its GoString and assume it'll
// follow the usual GoString conventions.
b.WriteString(ty.FriendlyName())
}
}
func indentSpaces(level int) string {
return strings.Repeat(" ", level)
}