autoload: resolving the solution file based on a function

autoload/OmniSharp.vim

@@ -108,12 +108,16 @@ function! OmniSharp#FindSolutionOrDir(...) abort
   let interactive = a:0 ? a:1 : 1
   let bufnr = a:0 > 1 ? a:2 : bufnr('%')
   if empty(getbufvar(bufnr, 'OmniSharp_buf_server'))
-    try
-      let sln = s:FindSolution(interactive, bufnr)
-      call setbufvar(bufnr, 'OmniSharp_buf_server', sln)
-    catch
-      return ''
-    endtry
+    if exists('g:OmniSharp_find_solution')
+      let sln = call(g:OmniSharp_find_solution, [bufnr])
+    else
+      try
+        let sln = s:FindSolution(interactive, bufnr)
+      catch
+        return ''
+      endtry
+    endif
+    call setbufvar(bufnr, 'OmniSharp_buf_server', sln)
   endif
   return getbufvar(bufnr, 'OmniSharp_buf_server')
 endfunction

doc/omnisharp-vim.txt

@@ -190,6 +190,22 @@ Default: {} >
     \ 'C:\path\to\other\project': 2004,
     \}
 <
+                                                      *g:OmniSharp_find_solution*
+Function used to resolve the solution file anytime it needs to be resolved
+based on the currently opened file.
+
+This can be used in various ways, but one particular use case might be when
+you need Omnisharp to stick to a given solution file that would contain all
+the projects that you need to work with even though you navigate to
+subprojects where other solution files could be found there. In that case, one
+could pass a value along the following lines: >
+    let g:OmniSharp_find_solution = {bufnr -> "/path/to/main_project.sln"}
+<
+
+This is a lambda expression that always evaluates to the string
+`/the/path/to/my/main_project.sln`. One could imagine more complexed cases.
+It's up to the user to use this as he sees fit.
+
 -------------------------------------------------------------------------------
 3.2 DIAGNOSTICS                                    *omnisharp-diagnostic-options*