create lang/format package

Create a single place to generate some common formats, mostly the format
of a cty.Path. These were used in the tfdiags package, but need to be
split out to prevent import cycles if we want to use them in any core
package.

internal/lang/format/format.go

@@ -0,0 +1,68 @@
+// Copyright (c) HashiCorp, Inc.
+// SPDX-License-Identifier: BUSL-1.1
+
+package format
+
+import (
+	"fmt"
+	"strconv"
+	"strings"
+
+	"github.com/zclconf/go-cty/cty"
+)
+
+// CtyPath is a helper function to produce a user-friendly string
+// representation of a cty.Path. The result uses a syntax similar to the
+// HCL expression language in the hope of it being familiar to users.
+func CtyPath(path cty.Path) string {
+	var buf strings.Builder
+	for _, step := range path {
+		switch ts := step.(type) {
+		case cty.GetAttrStep:
+			fmt.Fprintf(&buf, ".%s", ts.Name)
+		case cty.IndexStep:
+			buf.WriteByte('[')
+			key := ts.Key
+			keyTy := key.Type()
+			switch {
+			case key.IsNull():
+				buf.WriteString("null")
+			case !key.IsKnown():
+				buf.WriteString("(not yet known)")
+			case keyTy == cty.Number:
+				bf := key.AsBigFloat()
+				buf.WriteString(bf.Text('g', -1))
+			case keyTy == cty.String:
+				buf.WriteString(strconv.Quote(key.AsString()))
+			default:
+				buf.WriteString("...")
+			}
+			buf.WriteByte(']')
+		}
+	}
+	return buf.String()
+}
+
+// ErrorDiag is a helper function to produce a user-friendly string
+// representation of certain special error types that we might want to
+// include in diagnostic messages.
+func ErrorDiag(err error) string {
+	perr, ok := err.(cty.PathError)
+	if !ok || len(perr.Path) == 0 {
+		return err.Error()
+	}
+
+	return fmt.Sprintf("%s: %s", CtyPath(perr.Path), perr.Error())
+}
+
+// ErrorDiagPrefixed is like Error except that it presents any path
+// information after the given prefix string, which is assumed to contain
+// an HCL syntax representation of the value that errors are relative to.
+func ErrorDiagPrefixed(err error, prefix string) string {
+	perr, ok := err.(cty.PathError)
+	if !ok || len(perr.Path) == 0 {
+		return fmt.Sprintf("%s: %s", prefix, err.Error())
+	}
+
+	return fmt.Sprintf("%s%s: %s", prefix, CtyPath(perr.Path), perr.Error())
+}

internal/tfdiags/config_traversals.go

@@ -4,68 +4,23 @@
 package tfdiags
 
 import (
-	"fmt"
-	"strconv"
-	"strings"
-
-	"github.com/zclconf/go-cty/cty"
+	"github.com/hashicorp/terraform/internal/lang/format"
 )
 
+// These functions have been moved to the format package to allow for imports
+// which would otherwise cause cycles.
+
 // FormatCtyPath is a helper function to produce a user-friendly string
 // representation of a cty.Path. The result uses a syntax similar to the
 // HCL expression language in the hope of it being familiar to users.
-func FormatCtyPath(path cty.Path) string {
-	var buf strings.Builder
-	for _, step := range path {
-		switch ts := step.(type) {
-		case cty.GetAttrStep:
-			fmt.Fprintf(&buf, ".%s", ts.Name)
-		case cty.IndexStep:
-			buf.WriteByte('[')
-			key := ts.Key
-			keyTy := key.Type()
-			switch {
-			case key.IsNull():
-				buf.WriteString("null")
-			case !key.IsKnown():
-				buf.WriteString("(not yet known)")
-			case keyTy == cty.Number:
-				bf := key.AsBigFloat()
-				buf.WriteString(bf.Text('g', -1))
-			case keyTy == cty.String:
-				buf.WriteString(strconv.Quote(key.AsString()))
-			default:
-				buf.WriteString("...")
-			}
-			buf.WriteByte(']')
-		}
-	}
-	return buf.String()
-}
+var FormatCtyPath = format.CtyPath
 
 // FormatError is a helper function to produce a user-friendly string
 // representation of certain special error types that we might want to
 // include in diagnostic messages.
-//
-// This currently has special behavior only for cty.PathError, where a
-// non-empty path is rendered in a HCL-like syntax as context.
-func FormatError(err error) string {
-	perr, ok := err.(cty.PathError)
-	if !ok || len(perr.Path) == 0 {
-		return err.Error()
-	}
-
-	return fmt.Sprintf("%s: %s", FormatCtyPath(perr.Path), perr.Error())
-}
+var FormatError = format.ErrorDiag
 
 // FormatErrorPrefixed is like FormatError except that it presents any path
 // information after the given prefix string, which is assumed to contain
 // an HCL syntax representation of the value that errors are relative to.
-func FormatErrorPrefixed(err error, prefix string) string {
-	perr, ok := err.(cty.PathError)
-	if !ok || len(perr.Path) == 0 {
-		return fmt.Sprintf("%s: %s", prefix, err.Error())
-	}
-
-	return fmt.Sprintf("%s%s: %s", prefix, FormatCtyPath(perr.Path), perr.Error())
-}
+var FormatErrorPrefixed = format.ErrorDiagPrefixed