test: don't try to read the journal

hledger/Hledger/Cli/Commands.hs

@@ -230,8 +230,12 @@ testmode = (defCommandMode ["test"]) {
  }
 
 -- | Run some or all hledger-lib and hledger unit tests, and exit with success or failure.
+--
+-- Unlike other hledger commands, this one does not operate on the user's Journal.
+-- For ease of implementation the Journal parameter remains in the type signature, 
+-- but it will not be valid and should not be used.
 testcmd :: CliOpts -> Journal -> IO ()
-testcmd opts _ = do
+testcmd opts _donotuse = do
   let ts = 
         (if tree_ $ reportopts_ opts then matchedTestsTree else matchedTestsFlat) 
           opts tests_Hledger_Cli_Commands

hledger/Hledger/Cli/Main.hs

@@ -169,14 +169,17 @@ main = do
       | isBadCommand             = badCommandError
 
       -- builtin commands
-      | Just (cmdmode, cmdaction) <- findCommand cmd = do 
-        if cmd=="add" -- add command does extra work before reading journal
-        then (do
-          journalFilePathFromOpts opts >>= (ensureJournalFileExists . head) 
-          withJournalDo opts cmdaction)
-          `orShowHelp` cmdmode
-        else
-          withJournalDo opts cmdaction `orShowHelp` cmdmode
+      | Just (cmdmode, cmdaction) <- findCommand cmd =
+        (case cmd of
+          "test" -> -- should not read the journal
+            cmdaction opts (error "journal-less command tried to use the journal")
+          "add" ->  -- should create the journal if missing
+            (ensureJournalFileExists =<< (head <$> journalFilePathFromOpts opts)) >>
+            withJournalDo opts cmdaction
+          _ ->      -- all other commands: read the journal or fail if missing
+            withJournalDo opts cmdaction
+        )
+        `orShowHelp` cmdmode
 
       -- addon commands
       | isExternalCommand = do