fix(weidu-d): keep formatter idempotent when a ~string~ abuts a keyword

A transition trigger written with no space before THEN (~..NOTVALID)~THEN,
valid WeiDU) formatted to ~..~THEN on the first pass but ~..~ THEN once the
broken line was reparsed, so the formatter was not idempotent and the
external format sweep failed on BG1NPC's x#faint.d.

normalizeTransitionText now inserts a separating space at a ~/"-delimited
string <-> word-character boundary (either direction), so the trigger and the
following keyword are always spaced. %-delimited strings are deliberately
excluded: %var%-interpolated names (%tutu_var%KELDDA, TAZOK%eet_var%) abut
literal text on purpose and must not be split.

Unparks x#faint.d (previously excluded for this bug). Full IE format sweep is
green with it back in; added a CLI idempotence regression test.

Author: burner1024

external/infinity-engine-exclude.txt

@@ -210,6 +210,3 @@ BG1NPC/bg1npc/phase2/tpa/bg1npc_xzarqst.tpa
 # BG1NPC malformed D file (weidu rejects it; unresolvable %macro% used as standalone CHAIN content)
 BG1NPC/bg1npc/phase2/dlg/x#kivantazok_ee.d
 
-# BG1NPC valid dialog parked for a pre-existing formatter idempotency bug (not malformed):
-# ~string~ abutting THEN with no source space normalizes inconsistently. Tracked separately; unpark after fixing normalizeTransitionText.
-BG1NPC/bg1npc/phase2/dlg/x#faint.d

format/src/weidu-d/core.ts

@@ -87,22 +87,31 @@ function isNextFeature(node: SyntaxNode): boolean {
     );
 }
 
-// Normalize transition text: collapse whitespace in code, preserve strings and block comments exactly
+// True when a `~`/`"` string delimiter directly abuts a word character (in either order). That is the
+// spot that renders as `~trigger~THEN` from a no-space source and reformats to `~trigger~ THEN`,
+// breaking idempotency. `%` is deliberately excluded: %var%-interpolated names (%tutu_var%KELDDA,
+// TAZOK%eet_var%) abut literal text on purpose and must never be split by a space.
+function needsBoundarySpace(prev: string, next: string): boolean {
+    const isTildeOrQuote = (c: string): boolean => c === "~" || c === '"';
+    const isWord = (c: string): boolean => /\w/.test(c);
+    return (isTildeOrQuote(prev) && isWord(next)) || (isWord(prev) && isTildeOrQuote(next));
+}
+
+// Normalize transition text: collapse whitespace in code, preserve strings and block comments exactly,
+// and insert a separating space where a ~/"-string abuts a word with none (so `~..~THEN` is stable).
 function normalizeTransitionText(text: string): string {
     const tokens = tokenizeWeidu(text);
-    const parts: string[] = [];
+    let result = "";
 
     for (const token of tokens) {
-        if (token.type === WeiduTokenType.Code) {
-            // Collapse whitespace in code parts
-            parts.push(token.text.replaceAll(/\s+/g, " "));
-        } else {
-            // Preserve strings and comments exactly as-is
-            parts.push(token.text);
+        const part = token.type === WeiduTokenType.Code ? token.text.replaceAll(/\s+/g, " ") : token.text;
+        if (part.length > 0 && result.length > 0 && needsBoundarySpace(result[result.length - 1]!, part[0]!)) {
+            result += " ";
         }
+        result += part;
     }
 
-    return parts.join("").trim();
+    return result.trim();
 }
 
 // Get line length excluding comment

format/test/format-cli.test.ts

@@ -353,4 +353,22 @@ describe("format CLI integration", () => {
             expect(code).toBe(0);
         });
     });
+
+    describe("weidu-d transition idempotence", () => {
+        // Regression: a ~trigger~ string abutting THEN with no source space (valid WeiDU) rendered as
+        // ~..~THEN on the first pass but ~..~ THEN once the broken transition line was reparsed, so the
+        // formatter was not idempotent. A separating space is now inserted at a ~/"-string<->word
+        // boundary (never a %var% one, so interpolated names stay abutted).
+        it("adds a stable space between a ~trigger~ and an abutting THEN across a line break", () => {
+            const input =
+                "EXTEND_BOTTOM ~%tutu_var%CORSON~ 6\n" +
+                'IF ~InParty("faldorn") InMyArea("faldorn") !StateCheck("faldorn",CD_STATE_NOTVALID)~THEN EXTERN ~%FALDORN_JOINED%~ FaldornCorsone\n' +
+                "END\n";
+            const file = path.join(tmpDir, "trans.d");
+            fs.writeFileSync(file, input);
+            const { code, stderr } = run(file, "--save-and-check");
+            expect(stderr).not.toContain("Formatter not idempotent");
+            expect(code).toBe(0);
+        });
+    });
 });