As I read the code, the problem is that the wiki page content does not include the title of the page, causing it not to be indexed.

I think this can be addressed by explicitly setting the title for the search in get_stext_by_mimetype() for wiki pages. The patch below allows for that.

In my testing, this works for wiki pages and I did not see differences for checkins, docs, forums or tickets.

BTW, after initializing the title Blob like this, the many calls to add the title to pOut and calling markdown_to_html() became fairly repetitive to look at. I took it a notch further and dealt with these after handling the mimetypes. It may be too much, but I felt this better separated the code in to first handling different mimetypes for the purpose of determining the title and converting to HTML, followed by generating the resulting text in pOut.

Index: src/search.c
==================================================================
--- src/search.c
+++ src/search.c
@@ -1229,50 +1229,52 @@
 
 /*
 ** This is a helper function for search_stext().  Writing into pOut
 ** the search text obtained from pIn according to zMimetype.
 **
+** If a title is not specified in zTitle (e.g. for wiki pages that do not
+** include the title in the body), it is determined from the page content.
+**
 ** The title of the document is the first line of text.  All subsequent
 ** lines are the body.  If the document has no title, the first line
 ** is blank.
 */
 static void get_stext_by_mimetype(
   Blob *pIn,
   const char *zMimetype,
+  const char *zTitle,
   Blob *pOut
 ){
   Blob html, title;
+  Blob *pHtml = &html;
   blob_init(&html, 0, 0);
-  blob_init(&title, 0, 0);
+  if( zTitle==0 ){
+    blob_init(&title, 0, 0);
+  }else{
+    blob_init(&title, zTitle, -1);
+  }
   if( zMimetype==0 ) zMimetype = "text/plain";
   if( fossil_strcmp(zMimetype,"text/x-fossil-wiki")==0 ){
-    Blob tail;
-    blob_init(&tail, 0, 0);
-    if( wiki_find_title(pIn, &title, &tail) ){
-      blob_appendf(pOut, "%s\n", blob_str(&title));
+    if( blob_size(&title) ){
+      wiki_convert(pIn, &html, 0);
+    }else{
+      Blob tail;
+      blob_init(&tail, 0, 0);
+      wiki_find_title(pIn, &title, &tail);
       wiki_convert(&tail, &html, 0);
       blob_reset(&tail);
-    }else{
-      blob_append(pOut, "\n", 1);
-      wiki_convert(pIn, &html, 0);
     }
-    html_to_plaintext(blob_str(&html), pOut);
   }else if( fossil_strcmp(zMimetype,"text/x-markdown")==0 ){
-    markdown_to_html(pIn, &title, &html);
-    if( blob_size(&title) ){
-      blob_appendf(pOut, "%s\n", blob_str(&title));
-    }else{
-      blob_append(pOut, "\n", 1);
-    }
-    html_to_plaintext(blob_str(&html), pOut);
+    markdown_to_html(pIn, blob_size(&title) ? NULL : &title, &html);
   }else if( fossil_strcmp(zMimetype,"text/html")==0 ){
-    if( doc_is_embedded_html(pIn, &title) ){
-      blob_appendf(pOut, "%s\n", blob_str(&title));
-    }
-    html_to_plaintext(blob_str(pIn), pOut);
+    if( blob_size(&title)==0 ) doc_is_embedded_html(pIn, &title);
+    pHtml = pIn;
+  }
+  blob_appendf(pOut, "%s\n", blob_str(&title));
+  if( blob_size(pHtml) ){
+    html_to_plaintext(blob_str(pHtml), pOut);
   }else{
-    blob_append(pOut, "\n", 1);
     blob_append(pOut, blob_buffer(pIn), blob_size(pIn));
   }
   blob_reset(&html);
   blob_reset(&title);
 }
@@ -1305,11 +1307,11 @@
       blob_appendf(pAccum, "%s: %s |\n", zColName, db_column_text(pQuery,i));
     }else{
       Blob txt;
       blob_init(&txt, db_column_text(pQuery,i), -1);
       blob_appendf(pAccum, "%s: ", zColName);
-      get_stext_by_mimetype(&txt, zMime, pAccum);
+      get_stext_by_mimetype(&txt, zMime, NULL, pAccum);
       blob_append(pAccum, " |", 2);
       blob_reset(&txt);
     }
   }
 }
@@ -1344,11 +1346,11 @@
   switch( cType ){
     case 'd': {   /* Documents */
       Blob doc;
       content_get(rid, &doc);
       blob_to_utf8_no_bom(&doc, 0);
-      get_stext_by_mimetype(&doc, mimetype_from_name(zName), pOut);
+      get_stext_by_mimetype(&doc, mimetype_from_name(zName), NULL, pOut);
       blob_reset(&doc);
       break;
     }
     case 'f':     /* Forum messages */
     case 'e':     /* Tech Notes */
@@ -1366,11 +1368,11 @@
         blob_appendf(&wiki, "From %s:\n\n%s", pWiki->zUser, pWiki->zWiki);
       }else{
         blob_init(&wiki, pWiki->zWiki, -1);
       }
       get_stext_by_mimetype(&wiki, wiki_filter_mimetypes(pWiki->zMimetype),
-                            pOut);
+                            cType=='w' ? pWiki->zWikiTitle : NULL, pOut);
       blob_reset(&wiki);
       manifest_destroy(pWiki);
       break;
     }
     case 'c': {   /* Check-in Comments */
@@ -1396,11 +1398,11 @@
           db_column_blob(&q, 0, pOut);
         }else{
           Blob x;
           blob_init(&x,0,0);
           db_column_blob(&q, 0, &x);
-          get_stext_by_mimetype(&x, "text/x-fossil-wiki", pOut);
+          get_stext_by_mimetype(&x, "text/x-fossil-wiki", NULL, pOut);
           blob_reset(&x);
         }
       }
       db_reset(&q);
       break;
@@ -1507,11 +1509,11 @@
   Blob in, out;
   db_find_and_open_repository(0,0);
   if( g.argc!=4 ) usage("FILENAME MIMETYPE");
   blob_read_from_file(&in, g.argv[2], ExtFILE);
   blob_init(&out, 0, 0);
-  get_stext_by_mimetype(&in, g.argv[3], &out);
+  get_stext_by_mimetype(&in, g.argv[3], NULL, &out);
   fossil_print("%s\n",blob_str(&out));
   blob_reset(&in);
   blob_reset(&out);
 }