feat(forge): add validate option for forge ref validation on write (#138)

Problem: Typos in forge refs like `gh:user/repo#42` silently persist —
there's no feedback when a ref points to a nonexistent issue.

Solution: Add `forge.validate` config option. When enabled, `diff.apply()`
returns new/changed `ForgeRef[]` and `forge.validate_refs()` fetches
metadata for each, logging specific warnings for not-found, auth, or
CLI-missing errors.

lua/pending/config.lua

@@ -41,6 +41,7 @@
 
 ---@class pending.ForgeConfig
 ---@field close? boolean
+---@field validate? boolean
 ---@field warn_missing_cli? boolean
 ---@field [string] pending.ForgeInstanceConfig
 
@@ -155,6 +156,7 @@ local defaults = {
   sync = {},
   forge = {
     close = false,
+    validate = false,
     warn_missing_cli = true,
     github = {
       icon = '',

lua/pending/diff.lua

@@ -82,14 +82,26 @@ function M.parse_buffer(lines)
   return result
 end
 
+---@param a? pending.ForgeRef
+---@param b? pending.ForgeRef
+---@return boolean
+local function refs_equal(a, b)
+  if not a or not b then
+    return false
+  end
+  return a.forge == b.forge and a.owner == b.owner
+    and a.repo == b.repo and a.number == b.number
+end
+
 ---@param lines string[]
 ---@param s pending.Store
 ---@param hidden_ids? table<integer, true>
----@return nil
+---@return pending.ForgeRef[]
 function M.apply(lines, s, hidden_ids)
   local parsed = M.parse_buffer(lines)
   local now = timestamp()
   local data = s:data()
+  local new_refs = {} ---@type pending.ForgeRef[]
 
   local old_by_id = {}
   for _, task in ipairs(data.tasks) do
@@ -120,6 +132,9 @@ function M.apply(lines, s, hidden_ids)
           order = order_counter,
           _extra = entry.forge_ref and { _forge_ref = entry.forge_ref } or nil,
         })
+        if entry.forge_ref then
+          table.insert(new_refs, entry.forge_ref)
+        end
       else
         seen_ids[entry.id] = true
         local task = old_by_id[entry.id]
@@ -154,6 +169,10 @@ function M.apply(lines, s, hidden_ids)
           end
         end
         if entry.forge_ref ~= nil then
+          local old_ref = task._extra and task._extra._forge_ref or nil
+          if not refs_equal(old_ref, entry.forge_ref) then
+            table.insert(new_refs, entry.forge_ref)
+          end
           if not task._extra then
             task._extra = {}
           end
@@ -188,6 +207,9 @@ function M.apply(lines, s, hidden_ids)
         order = order_counter,
         _extra = entry.forge_ref and { _forge_ref = entry.forge_ref } or nil,
       })
+      if entry.forge_ref then
+        table.insert(new_refs, entry.forge_ref)
+      end
     end
 
     ::continue::
@@ -202,6 +224,7 @@ function M.apply(lines, s, hidden_ids)
   end
 
   s:save()
+  return new_refs
 end
 
 return M

lua/pending/forge.lua

@@ -243,30 +243,51 @@ function M.format_label(ref, cache)
   return text, hl
 end
 
+---@class pending.ForgeFetchError
+---@field code 'not_found'|'auth'|'cli_missing'|'network'
+---@field message string
+
 ---@param ref pending.ForgeRef
----@param callback fun(cache: pending.ForgeCache?)
+---@param callback fun(cache: pending.ForgeCache?, err: pending.ForgeFetchError?)
 function M.fetch_metadata(ref, callback)
   local args = M._api_args(ref)
+  local backend = _by_name[ref.forge]
+
+  if backend and vim.fn.executable(backend.cli) == 0 then
+    vim.schedule(function()
+      local forge_cfg = config.get().forge or {}
+      if forge_cfg.warn_missing_cli ~= false and not backend._warned then
+        backend._warned = true
+        log.warn(('%s not installed'):format(backend.cli))
+      end
+      callback(nil, { code = 'cli_missing', message = backend.cli .. ' not installed' })
+    end)
+    return
+  end
 
   vim.system(args, { text = true }, function(result)
     if result.code ~= 0 or not result.stdout or result.stdout == '' then
-      local forge_cfg = config.get().forge or {}
-      local backend = _by_name[ref.forge]
-      if backend and forge_cfg.warn_missing_cli ~= false and not backend._warned then
-        backend._warned = true
-        vim.system(backend.auth_status_args, { text = true }, function(auth_result)
-          vim.schedule(function()
-            if auth_result.code ~= 0 then
-              log.warn(('%s not authenticated — run `%s`'):format(backend.cli, backend.auth_cmd))
-            end
-            callback(nil)
-          end)
-        end)
-      else
-        vim.schedule(function()
-          callback(nil)
-        end)
+      local stderr = result.stderr or ''
+      local err_code = 'network' ---@type 'not_found'|'auth'|'network'
+      if stderr:find('404') or stderr:find('Not Found') then
+        err_code = 'not_found'
+      elseif stderr:find('401') or stderr:find('requires authentication') then
+        err_code = 'auth'
       end
+      vim.schedule(function()
+        local forge_cfg = config.get().forge or {}
+        if
+          backend
+          and forge_cfg.warn_missing_cli ~= false
+          and not backend._warned
+        then
+          backend._warned = true
+          log.warn(
+            ('%s not found or not authenticated — run `%s`'):format(backend.cli, backend.auth_cmd)
+          )
+        end
+        callback(nil, { code = err_code, message = stderr })
+      end)
       return
     end
     local ok, decoded = pcall(vim.json.decode, result.stdout)
@@ -567,4 +588,31 @@ M.register({
   end,
 })
 
+---@param refs pending.ForgeRef[]
+function M.validate_refs(refs)
+  local forge_cfg = config.get().forge or {}
+  if not forge_cfg.validate then
+    return
+  end
+  for _, ref in ipairs(refs) do
+    M.fetch_metadata(ref, function(_, err)
+      if err then
+        local label = ref.owner .. '/' .. ref.repo .. '#' .. ref.number
+        local backend = _by_name[ref.forge]
+        if err.code == 'not_found' then
+          log.warn(('%s not found — check owner, repo, and number'):format(label))
+        elseif err.code == 'auth' then
+          local cmd = backend and backend.auth_cmd or 'auth'
+          log.warn(('%s: not authenticated — run `%s`'):format(label, cmd))
+        elseif err.code == 'cli_missing' then
+          local cli = backend and backend.cli or 'cli'
+          log.warn(('%s: %s not installed'):format(label, cli))
+        else
+          log.warn(('%s: validation failed'):format(label))
+        end
+      end
+    end)
+  end
+end
+
 return M

lua/pending/init.lua

@@ -489,9 +489,13 @@ function M._on_write(bufnr)
   if #stack > UNDO_MAX then
     table.remove(stack, 1)
   end
-  diff.apply(lines, s, hidden)
+  local new_refs = diff.apply(lines, s, hidden)
   M._recompute_counts()
   buffer.render(bufnr)
+  if new_refs and #new_refs > 0 then
+    local forge = require('pending.forge')
+    forge.validate_refs(new_refs)
+  end
 end
 
 ---@return nil