Fix #170: support .svelte and other code files with unrecognized MIME types

src/app/services/file-download-service.ts

@@ -108,7 +108,48 @@ const APPLICATION_TEXT_MIME_TYPES = new Set([
   "application/sql",
 ]);
 
-export function isTextMimeType(mimeType: string | undefined): boolean {
+const TEXT_FILE_EXTENSIONS = new Set([
+  "svelte",
+  "vue",
+  "ts",
+  "tsx",
+  "jsx",
+  "mjs",
+  "cjs",
+  "go",
+  "rs",
+  "rb",
+  "py",
+  "java",
+  "c",
+  "cpp",
+  "h",
+  "hpp",
+  "cs",
+  "swift",
+  "kt",
+  "kts",
+  "sh",
+  "bash",
+  "yaml",
+  "yml",
+  "toml",
+  "ini",
+  "cfg",
+  "md",
+  "mdx",
+  "css",
+  "scss",
+  "less",
+  "html",
+  "htm",
+  "graphql",
+  "gql",
+  "proto",
+  "gradle",
+]);
+
+export function isTextMimeType(mimeType: string | undefined, filename?: string): boolean {
   if (!mimeType) {
     return false;
   }
@@ -117,5 +158,16 @@ export function isTextMimeType(mimeType: string | undefined): boolean {
     return true;
   }
 
-  return APPLICATION_TEXT_MIME_TYPES.has(mimeType);
+  if (APPLICATION_TEXT_MIME_TYPES.has(mimeType)) {
+    return true;
+  }
+
+  if (filename) {
+    const ext = filename.split(".").pop()?.toLowerCase();
+    if (ext && TEXT_FILE_EXTENSIONS.has(ext)) {
+      return true;
+    }
+  }
+
+  return false;
 }

src/bot/handlers/document-handler.ts

@@ -50,7 +50,7 @@ export async function handleDocumentMessage(
   const filename = doc.file_name || "document";
 
   try {
-    if (isTextMimeType(mimeType)) {
+    if (isTextMimeType(mimeType, filename)) {
       if (!isFileSizeAllowed(doc.file_size, config.files.maxFileSizeKb)) {
         logger.warn(
           `[Document] Text file too large: ${filename} (${doc.file_size} bytes > ${config.files.maxFileSizeKb}KB)`,

src/bot/handlers/media-group-handler.ts

@@ -254,7 +254,7 @@ export class MediaGroupAttachmentHandler {
       const mimeType = document.mime_type || "";
       const filename = document.file_name || "document";
 
-      if (isTextMimeType(mimeType)) {
+      if (isTextMimeType(mimeType, filename)) {
         if (!isFileSizeAllowed(document.file_size, config.files.maxFileSizeKb)) {
           return { reason: "text_file_too_large" };
         }

tests/app/services/file-download-service.test.ts

@@ -114,6 +114,36 @@ describe("app/services/file-download-service", () => {
     it("returns false for empty string", () => {
       expect(isTextMimeType("")).toBe(false);
     });
+
+    it("returns true for unknown MIME with known code file extension", () => {
+      expect(isTextMimeType("application/octet-stream", "component.svelte")).toBe(true);
+      expect(isTextMimeType("application/octet-stream", "App.vue")).toBe(true);
+      expect(isTextMimeType("application/octet-stream", "main.tsx")).toBe(true);
+      expect(isTextMimeType("application/octet-stream", "server.go")).toBe(true);
+      expect(isTextMimeType("application/octet-stream", "script.py")).toBe(true);
+    });
+
+    it("returns false for unknown MIME with unknown extension", () => {
+      expect(isTextMimeType("application/octet-stream", "file.xyz")).toBe(false);
+      expect(isTextMimeType("application/octet-stream", "archive.7z")).toBe(false);
+    });
+
+    it("returns false for unknown MIME without filename", () => {
+      expect(isTextMimeType("application/octet-stream")).toBe(false);
+    });
+
+    it("returns false for undefined MIME even with known extension", () => {
+      expect(isTextMimeType(undefined, "file.svelte")).toBe(false);
+    });
+
+    it("handles files with multiple dots correctly", () => {
+      expect(isTextMimeType("application/octet-stream", "Component.test.svelte")).toBe(true);
+      expect(isTextMimeType("application/octet-stream", "some.file.with.dots.py")).toBe(true);
+    });
+
+    it("handles files with no extension", () => {
+      expect(isTextMimeType("application/octet-stream", "Dockerfile")).toBe(false);
+    });
   });
 });