diffs: share language hint validation

extensions/diffs/src/language-hints.ts

@@ -0,0 +1,39 @@
+import { resolveLanguage } from "@pierre/diffs";
+import type { SupportedLanguages } from "@pierre/diffs";
+
+const PASSTHROUGH_LANGUAGE_HINTS = new Set<SupportedLanguages>(["ansi", "text"]);
+
+export async function normalizeSupportedLanguageHint(
+  value?: string,
+): Promise<SupportedLanguages | undefined> {
+  const normalized = value?.trim();
+  if (!normalized) {
+    return undefined;
+  }
+  if (PASSTHROUGH_LANGUAGE_HINTS.has(normalized as SupportedLanguages)) {
+    return normalized as SupportedLanguages;
+  }
+  try {
+    await resolveLanguage(normalized as Exclude<SupportedLanguages, "text" | "ansi">);
+    return normalized as SupportedLanguages;
+  } catch {
+    return undefined;
+  }
+}
+
+export async function filterSupportedLanguageHints(
+  values: Iterable<string>,
+): Promise<SupportedLanguages[]> {
+  const supported = new Set<SupportedLanguages>();
+  for (const value of values) {
+    const normalized = await normalizeSupportedLanguageHint(value);
+    if (!normalized) {
+      continue;
+    }
+    supported.add(normalized);
+  }
+  if (supported.size === 0) {
+    supported.add("text");
+  }
+  return [...supported];
+}

extensions/diffs/src/render.ts

@@ -1,6 +1,7 @@
 import type { FileContents, FileDiffMetadata, SupportedLanguages } from "@pierre/diffs";
-import { parsePatchFiles, resolveLanguage } from "@pierre/diffs";
+import { parsePatchFiles } from "@pierre/diffs";
 import { preloadFileDiff, preloadMultiFileDiff } from "@pierre/diffs/ssr";
+import { normalizeSupportedLanguageHint } from "./language-hints.js";
 import { ensurePierreThemesRegistered } from "./pierre-themes.js";
 import type {
   DiffInput,
@@ -178,22 +179,6 @@ function buildRenderVariants(params: { options: DiffRenderOptions; target: DiffR
   };
 }
 
-async function normalizeSupportedLanguage(value?: string): Promise<SupportedLanguages | undefined> {
-  const normalized = value?.trim();
-  if (!normalized) {
-    return undefined;
-  }
-  if (normalized === "text" || normalized === "ansi") {
-    return normalized;
-  }
-  try {
-    await resolveLanguage(normalized as Exclude<SupportedLanguages, "text" | "ansi">);
-    return normalized as SupportedLanguages;
-  } catch {
-    return undefined;
-  }
-}
-
 function buildPayloadLanguages(payload: {
   fileDiff?: FileDiffMetadata;
   oldFile?: FileContents;
@@ -363,7 +348,7 @@ async function renderBeforeAfterDiff(
 ): Promise<{ viewerBodyHtml?: string; imageBodyHtml?: string; fileCount: number }> {
   ensurePierreThemesRegistered();
 
-  const lang = await normalizeSupportedLanguage(input.lang);
+  const lang = await normalizeSupportedLanguageHint(input.lang);
   const fileName = resolveBeforeAfterFileName({ input, lang });
   const oldFile: FileContents = {
     name: fileName,

extensions/diffs/src/viewer-client.ts

@@ -1,10 +1,11 @@
-import { FileDiff, preloadHighlighter, resolveLanguage } from "@pierre/diffs";
+import { FileDiff, preloadHighlighter } from "@pierre/diffs";
 import type {
   FileContents,
   FileDiffMetadata,
   FileDiffOptions,
   SupportedLanguages,
 } from "@pierre/diffs";
+import { filterSupportedLanguageHints } from "./language-hints.js";
 import type { DiffViewerPayload, DiffLayout, DiffTheme } from "./types.js";
 import { parseViewerPayloadJson } from "./viewer-payload.js";
 
@@ -32,23 +33,7 @@ const viewerState: ViewerState = {
 export async function filterSupportedHydrationLanguages(
   languages: Iterable<string>,
 ): Promise<SupportedLanguages[]> {
-  const supported = new Set<SupportedLanguages>();
-  for (const language of languages) {
-    if (language === "text" || language === "ansi") {
-      supported.add(language);
-      continue;
-    }
-    try {
-      await resolveLanguage(language as Exclude<SupportedLanguages, "text" | "ansi">);
-      supported.add(language);
-    } catch {
-      // Ignore invalid persisted hints and let the viewer fall back to plain text.
-    }
-  }
-  if (supported.size === 0) {
-    supported.add("text");
-  }
-  return [...supported];
+  return filterSupportedLanguageHints(languages);
 }
 
 function parsePayload(element: HTMLScriptElement): DiffViewerPayload {