The generated TypeScript parser of a key form names its own parameter and locals apart from the form's parts

A key form such as <node>.<module>.<key> made the parser declare the parameter key and the part key together (TS2300 Duplicate identifier), which the per-package unit level now surfaces. The parameter and the locals are now _key, _rest and _at<n>; a test row with such a form fails on the old output. Issue 1966.

Claude-Session: https://claude.ai/code/session_01NcbgfFSnn24M3GcqttoU7i

modules/mesh-build-go/buildstep/seatgen/states.go

@@ -232,24 +232,24 @@ func tsStates(b *bytes.Buffer, states []seatdef.State) error {
 			}
 			fmt.Fprintf(b, "/** The key of one value of the state %s under the form %s. */\nexport function %sKey(%s): string {\n  return %s;\n}\n\n",
 				s.Name, strconv.Quote(kf.Key), fn, strings.Join(args, ", "), strings.Join(expr, " + "))
-			fmt.Fprintf(b, "/** The parts of a key of the form %s, or undefined for a key of another form. */\nexport function parse%sKey(key: string): { %s } | undefined {\n  let rest = key;\n",
+			fmt.Fprintf(b, "/** The parts of a key of the form %s, or undefined for a key of another form. */\nexport function parse%sKey(_key: string): { %s } | undefined {\n  let _rest = _key;\n",
 				strconv.Quote(kf.Key), ident(fn), strings.Join(fields, "; "))
 			for i := 0; i < len(ts); {
 				t := ts[i]
 				switch {
 				case !t.part:
-					fmt.Fprintf(b, "  if (!rest.startsWith(%s)) return undefined;\n  rest = rest.slice(%d);\n", strconv.Quote(t.text), len(t.text))
+					fmt.Fprintf(b, "  if (!_rest.startsWith(%s)) return undefined;\n  _rest = _rest.slice(%d);\n", strconv.Quote(t.text), len(t.text))
 					i++
 				case i+1 < len(ts):
-					fmt.Fprintf(b, "  const at%d = rest.indexOf(%s);\n  if (at%d <= 0) return undefined;\n  const %s = rest.slice(0, at%d);\n  rest = rest.slice(at%d + %d);\n",
+					fmt.Fprintf(b, "  const _at%d = _rest.indexOf(%s);\n  if (_at%d <= 0) return undefined;\n  const %s = _rest.slice(0, _at%d);\n  _rest = _rest.slice(_at%d + %d);\n",
 						i, strconv.Quote(ts[i+1].text), i, paramName(t.text), i, i, len(ts[i+1].text))
 					i += 2
 				default:
-					fmt.Fprintf(b, "  if (rest === \"\") return undefined;\n  const %s = rest;\n  rest = \"\";\n", paramName(t.text))
+					fmt.Fprintf(b, "  if (_rest === \"\") return undefined;\n  const %s = _rest;\n  _rest = \"\";\n", paramName(t.text))
 					i++
 				}
 			}
-			fmt.Fprintf(b, "  if (rest !== \"\") return undefined;\n  return { %s };\n}\n\n", strings.Join(got, ", "))
+			fmt.Fprintf(b, "  if (_rest !== \"\") return undefined;\n  return { %s };\n}\n\n", strings.Join(got, ", "))
 		}
 	}
 	return nil

modules/mesh-build-go/buildstep/seatgen/states_test.go

@@ -43,7 +43,10 @@ func TestAStateHasItsNamesKeyFormsAndStrictValues(t *testing.T) {
 	}
 	ts := string(files["ts/seats/aregistry/src/index.ts"])
 	for _, want := range []string{"export const states = {", "export function asksByAskerIDKey(asker: string, id: string): string",
-		"export function parseAsksByAskerIDKey(key: string)", "export interface AsksByAskerIDValue"} {
+		"export function parseAsksByAskerIDKey(_key: string)", "export interface AsksByAskerIDValue",
+		// a key form with a part named key: the parser's own parameter and locals are named apart from the parts
+		"export function parseAsksByNodeModuleKeyKey(_key: string): { node: string; module: string; key: string } | undefined",
+		"const key = _rest;"} {
 		if !strings.Contains(ts, want) {
 			t.Errorf("the seat's npm package lacks %q:\n%s", want, ts)
 		}

modules/mesh-build-go/buildstep/seatgen/testdata/contracts/seats/a-registry/seat.json

@@ -6,6 +6,7 @@
    "key-forms":[
     {"key":"<asker>.<id>","value":{"type":"object","properties":{"state":{"type":"string"},"since":{"type":"integer"}},"required":["state"]}},
     {"key":"<asker>.<id>.done","value":{"type":"object","properties":{"outcome":{"type":"string"}},"required":["outcome"]}},
+    {"key":"<node>.<module>.<key>","value":{"type":"object","description":"a part named key beside the parser's own parameter"}},
     {"key":"defaults","value":{"type":"object","description":"free"}}]},
   {"name":"local-name","template":"events","max-age-days":3,
    "key-forms":[{"key":"seen.<id-of-ask>","value":{"type":"string"}}]}]}