Add error message for diff viewer (#2255)

changelog.d/20250301_045106_github-actions[bot]_add-error-message-diff-viewer.rst

@@ -0,0 +1,7 @@
+.. _#2255:  https://github.com/fox0430/moe/pull/2255
+
+Added
+.....
+
+- `#2255`_ Add error message for diff viewer
+

src/moepkg/diffviewerutils.nim

@@ -1,6 +1,6 @@
 #[###################### GNU General Public License 3.0 ######################]#
 #                                                                              #
-#  Copyright (C) 2017─2023 Shuhei Nogawa                                       #
+#  Copyright (C) 2017─2025 Shuhei Nogawa                                       #
 #                                                                              #
 #  This program is free software: you can redistribute it and/or modify        #
 #  it under the terms of the GNU General Public License as published by        #
@@ -18,18 +18,24 @@
 #[############################################################################]#
 
 import std/[strformat, osproc, strutils]
+
+import pkg/results
+
 import unicodeext, highlight, color
 
-proc initDiffViewerBuffer*(sourceFilePath, backupFilePath: string): seq[Runes] =
+proc initDiffViewerBuffer*(
+    sourceFilePath, backupFilePath: string
+): Result[seq[Runes], string] =
   let cmdResult = execCmdEx(fmt"diff -u {sourceFilePath} {backupFilePath}")
-  # The diff command return 2 on failure.
   if cmdResult.exitCode == 2:
-    # TODO: Write the error message to the command window.
-    return @[ru""]
+    # The diff command return 2 on failure.
+    return Result[seq[Runes], string].err "diff command failed"
 
-  result = @[ru""]
+  var r = @[ru""]
   for line in cmdResult.output.splitLines:
-    result.add line.toRunes
+    r.add line.toRunes
+
+  return Result[seq[Runes], string].ok r
 
 proc initDiffViewerHighlight*(buffer: seq[Runes]): Highlight =
   for i, line in buffer:

src/moepkg/editorstatus.nim

@@ -405,9 +405,13 @@ proc addNewBuffer*(
       backupDir = backupDir(baseBackupDir, sourceFilePath)
       backupFilePath = backupDir / $currentLineBuffer
     status.bufStatus.add initBufferStatus(mode).get
-    status.bufStatus[^1].buffer =
-      initDiffViewerBuffer(sourceFilePath, backupFilePath).toGapBuffer
-    status.bufStatus[^1].path = backupFilePath.toRunes
+
+    let diffResult = initDiffViewerBuffer(sourceFilePath, backupFilePath)
+    if diffResult.isOk:
+      status.bufStatus[^1].buffer = diffResult.get.toGapBuffer
+      status.bufStatus[^1].path = backupFilePath.toRunes
+    else:
+      status.commandLine.writeDiffViewerError(diffResult.error)
   else:
     let b = initBufferStatus(path, mode)
     if b.isOk:

src/moepkg/messages.nim

@@ -336,6 +336,10 @@ proc writeBufferChangedWarn*(commandLine: var CommandLine, filename: Runes) =
   let mess = fmt"File {filename} has changed and the buffer was changed in Moe as well."
   commandLine.writeWarn(mess)
 
+proc writeDiffViewerError*(commandLine: var CommandLine, message: string) =
+  let mess = fmt"Error: diff: ${message}"
+  commandLine.writeError(mess)
+
 proc writeLspError*(commandLine: var CommandLine, message: string) =
   let mess = fmt"lsp: {message}"
   commandLine.writeError(mess)