X.P: Don't read/write to history file if size is 0

This contains a breaking change for readHistory, writeHistory,
historyCompletion, and historyCompletionP to take an XPConfig, so they
are aware of this choice. While the latter two are exported, it seems
unlikely to affect many users.

CHANGES.md

@@ -13,6 +13,13 @@
        order to lift any existing `IO StatusBarConfig` values into
        `X StatusBarConfig` values.
 
+  * `XMonad.Prompt`
+
+    - Added an additional `XPConfig` argument to `historyCompletion` and
+      `historyCompletionP`. Calls along the lines of `historyCompletionP
+      myFunc` should be changed to `historyCompletionP myConf myFunc`.
+      If not `myConf` is lying around, `def` can be used instead.
+
 ### New Modules
 
   * `XMonad.Actions.Profiles`.
@@ -37,6 +44,11 @@
 
     - Added `HH:MM-HH:MM` and `HH:MM+HH` syntax to specify time spans.
 
+  * `XMonad.Prompt`
+
+    - The history file is not extraneously read and written anymore if
+      the `historySize` is set to 0.
+
 ### Other changes
 
 ## 0.18.0 (February 3, 2024)

XMonad/Actions/Search.hs

@@ -437,14 +437,14 @@ namedEngine name (SearchEngine _ site) = searchEngineF name site
    browser. -}
 promptSearchBrowser :: XPConfig -> Browser -> SearchEngine -> X ()
 promptSearchBrowser config browser (SearchEngine name site) = do
-    hc <- historyCompletionP ("Search [" `isPrefixOf`)
+    hc <- historyCompletionP config ("Search [" `isPrefixOf`)
     mkXPrompt (Search name) config hc $ search browser site
 
 {- | Like 'promptSearchBrowser', but only suggest previous searches for the
    given 'SearchEngine' in the prompt. -}
 promptSearchBrowser' :: XPConfig -> Browser -> SearchEngine -> X ()
 promptSearchBrowser' config browser (SearchEngine name site) = do
-    hc <- historyCompletionP (searchName `isPrefixOf`)
+    hc <- historyCompletionP config (searchName `isPrefixOf`)
     mkXPrompt (Search name) config hc $ search browser site
   where
     searchName = showXPrompt (Search name)

XMonad/Actions/WorkspaceNames.hs

@@ -138,7 +138,7 @@ setCurrentWorkspaceName name = do
 -- | Prompt for a new name for the current workspace and set it.
 renameWorkspace :: XPConfig -> X ()
 renameWorkspace conf = do
-    completion <- historyCompletionP (prompt ==)
+    completion <- historyCompletionP conf (prompt ==)
     mkXPrompt (Wor prompt) conf completion setCurrentWorkspaceName
   where
     prompt = "Workspace name: "

XMonad/Prompt.hs

@@ -562,7 +562,7 @@ mkXPromptImplementation historyKey conf om = do
   s <- gets $ screenRect . W.screenDetail . W.current . windowset
   cleanMask <- cleanKeyMask
   cachedir <- asks (cacheDir . directories)
-  hist <- io $ readHistory cachedir
+  hist <- io $ readHistory conf cachedir
   fs <- initXMF (font conf)
   let width = getWinWidth s (position conf)
   st' <- io $
@@ -582,7 +582,7 @@ mkXPromptImplementation historyKey conf om = do
   releaseXMF fs
   when (successful st') $ do
     let prune = take (historySize conf)
-    io $ writeHistory cachedir $
+    io $ writeHistory conf cachedir $
       M.insertWith
       (\xs ys -> prune . historyFilter conf $ xs ++ ys)
       historyKey
@@ -1690,16 +1690,18 @@ emptyHistory = M.empty
 getHistoryFile :: FilePath -> FilePath
 getHistoryFile cachedir = cachedir ++ "/prompt-history"
 
-readHistory :: FilePath -> IO History
+readHistory :: XPConfig -> FilePath -> IO History
-readHistory cachedir = readHist `E.catch` \(SomeException _) -> return emptyHistory
+readHistory (XPC { historySize = 0 }) _ = return emptyHistory
+readHistory _ cachedir = readHist `E.catch` \(SomeException _) -> return emptyHistory
  where
     readHist = do
         let path = getHistoryFile cachedir
         xs <- withFile path ReadMode hGetLine
         readIO xs
 
-writeHistory :: FilePath -> History -> IO ()
+writeHistory :: XPConfig -> FilePath -> History -> IO ()
-writeHistory cachedir hist = do
+writeHistory (XPC { historySize = 0 }) _ _ = return ()
+writeHistory _ cachedir hist = do
   let path = getHistoryFile cachedir
       filtered = M.filter (not . null) hist
   writeFile path (show filtered) `E.catch` \(SomeException e) ->
@@ -1793,17 +1795,17 @@ breakAtSpace s
 -- | 'historyCompletion' provides a canned completion function much like
 --   'getShellCompl'; you pass it to mkXPrompt, and it will make completions work
 --   from the query history stored in the XMonad cache directory.
-historyCompletion :: X ComplFunction
+historyCompletion :: XPConfig -> X ComplFunction
-historyCompletion = historyCompletionP (const True)
+historyCompletion conf = historyCompletionP conf (const True)
 
 -- | Like 'historyCompletion' but only uses history data from Prompts whose
 -- name satisfies the given predicate.
-historyCompletionP :: (String -> Bool) -> X ComplFunction
+historyCompletionP :: XPConfig -> (String -> Bool) -> X ComplFunction
-historyCompletionP p = do
+historyCompletionP conf p = do
     cd <- asks (cacheDir . directories)
     pure $ \x ->
         let toComplList = deleteConsecutive . filter (isInfixOf x) . M.foldr (++) []
-         in toComplList . M.filterWithKey (const . p) <$> readHistory cd
+         in toComplList . M.filterWithKey (const . p) <$> readHistory conf cd
 
 -- | Sort a list and remove duplicates. Like 'deleteAllDuplicates', but trades off
 --   laziness and stability for efficiency.