Decode native diff paths without revalidation

docs/roadmap/audit/catalog.md

@@ -1,6 +1,6 @@
 # Consolidated audit catalog
 
-Status: **4 distinct open findings: 4 P3**, consolidated from 30
+Status: **3 distinct open findings: 3 P3**, consolidated from 30
 numbered entries in seven audit documents. Reviewed audit state:
 `db732e3a1de55c844f77870e1c6db683c2685d5d`.
 
@@ -507,6 +507,9 @@ construction becomes linear.
 
 ## F23 — P3: Concise diff rendering validates already-valid native paths
 
+**Complete.** The private decoder accepts ConfigKit's native path and performs
+single-pass token decoding. Focused diff, token and snapshot tests pass.
+
 ckconfig's private pointer decoder validates arbitrary strings even though its
 sole production caller supplies the canonical string of an immutable ConfigKit
 `Path`. Tests sustain malformed-input branches that this boundary cannot reach.

docs/roadmap/implementation.md

@@ -1,6 +1,6 @@
 # Audit remediation implementation plan
 
-Status: in progress; Stages 1–20 complete.
+Status: in progress; Stages 1–21 complete.
 
 Baseline: `d492c7747175c01a53261206c2b4356e53453621`. Before this sprint,
 intervening changes recorded decisions and retired the completed older
@@ -662,6 +662,11 @@ record these outcomes separately.
 
 ## Stage 21 — Decode native diff paths without revalidation
 
+**Complete.** Concise diff adaptation decodes tokens from native ConfigKit paths
+without revalidating arbitrary strings. Focused diff, pointer and snapshot tests
+pass offline in the aligned Go 1.27.0 workspace with `-mod=readonly`, including
+root, empty, Unicode and escaped keys.
+
 Findings: F23. Source: ckconfig `diff_report.go` and diff report tests.
 
 1. Change the private token helper to accept configkit.Path. Split its canonical

integrations/ckconfig/diff_report.go

@@ -8,39 +8,17 @@ import (
 	configkit "go.maximumdirect.net/configkit"
 )
 
-func decodeJSONPointer(pointer string) ([]string, error) {
+func decodeJSONPointer(path configkit.Path) []string {
+	pointer := path.String()
 	if pointer == "" {
-		return nil, nil
+		return nil
 	}
-	if pointer[0] != '/' {
-		return nil, fmt.Errorf("decode JSON pointer %q: path must start with /", pointer)
-	}
-
 	parts := strings.Split(pointer[1:], "/")
+	decoder := strings.NewReplacer("~1", "/", "~0", "~")
 	for index, part := range parts {
-		var decoded strings.Builder
-		decoded.Grow(len(part))
-		for offset := 0; offset < len(part); offset++ {
-			if part[offset] != '~' {
-				decoded.WriteByte(part[offset])
-				continue
-			}
-			if offset+1 >= len(part) {
-				return nil, fmt.Errorf("decode JSON pointer %q: incomplete escape in token %d", pointer, index)
-			}
-			offset++
-			switch part[offset] {
-			case '0':
-				decoded.WriteByte('~')
-			case '1':
-				decoded.WriteByte('/')
-			default:
-				return nil, fmt.Errorf("decode JSON pointer %q: invalid escape in token %d", pointer, index)
-			}
-		}
-		parts[index] = decoded.String()
+		parts[index] = decoder.Replace(part)
 	}
-	return parts, nil
+	return parts
 }
 
 func placeReportValue(root any, path []string, value any) (any, error) {
@@ -135,10 +113,7 @@ func renderDiffReport(differences []configkit.Difference) (any, error) {
 		if !difference.Right.Present {
 			continue
 		}
-		tokens, err := decodeJSONPointer(path)
-		if err != nil {
-			return nil, fmt.Errorf("difference at %q: %w", path, err)
-		}
+		tokens := decodeJSONPointer(difference.Path)
 		value, err := commandkit.DecodeYAMLReport(strings.NewReader(difference.Right.YAML))
 		if err != nil {
 			return nil, fmt.Errorf("difference at %q: %w", path, err)

integrations/ckconfig/diff_report_test.go

@@ -3,6 +3,8 @@ package ckconfig
 import (
 	"reflect"
 	"testing"
+
+	configkit "go.maximumdirect.net/configkit"
 )
 
 func TestDecodeJSONPointerPreservesSemanticTokens(t *testing.T) {
@@ -16,21 +18,18 @@ func TestDecodeJSONPointerPreservesSemanticTokens(t *testing.T) {
 		{pointer: "/0/../a.b/50%", want: []string{"0", "..", "a.b", "50%"}},
 		{pointer: "/a~1b/c~0d", want: []string{"a/b", "c~d"}},
 		{pointer: "/~01", want: []string{"~1"}},
+		{pointer: "/café", want: []string{"café"}},
 	}
 	for _, test := range tests {
-		got, err := decodeJSONPointer(test.pointer)
+		path, err := configkit.ParsePath(test.pointer)
 		if err != nil {
-			t.Fatalf("decode %q: %v", test.pointer, err)
+			t.Fatal(err)
 		}
+		got := decodeJSONPointer(path)
 		if !reflect.DeepEqual(got, test.want) {
 			t.Errorf("decode %q = %#v, want %#v", test.pointer, got, test.want)
 		}
 	}
-	for _, pointer := range []string{"missing-leading-slash", "/bad~", "/bad~2escape"} {
-		if _, err := decodeJSONPointer(pointer); err == nil {
-			t.Errorf("decode %q unexpectedly succeeded", pointer)
-		}
-	}
 }
 
 func TestPlaceReportValue(t *testing.T) {