Don't spuriously modify tags-table-list's global value #978
Conversation
This file contains bidirectional Unicode text that may be interpreted or compiled differently than what appears below. To review, open the file in an editor that reveals hidden Unicode characters.
Learn more about bidirectional Unicode characters
As part of haskell#592, commit 2b4e49c modified this code to alter the global value of tags-table-list as a side-effect, but this change was incorrect and causes problems elsewhere. Specifically, consider the following scenario: - User tries to jump to a definition with haskell-mode-jump-to-def-or-tag - That function falls back to haskell-mode-tag-find, which then calls haskell-mode-jump-to-tag This results in a call to haskell-process-generate-tags, which tries to run hasktags, whether or not it is installed. As a side effect, the global value of tags-table-list is set to include "/project/root/dir/TAGS", which was probably not even created properly (most people won't have hasktags installed). Then, imagine we're working in an unrelated project, and use Emacs' built-in completion-at-point functionality (or company-mode, which wraps it). Now, the tags-completion-at-point-function (enabled by default) sees and uses the modified value of tags-table-list, and errors noisily when called because that file does not exist. And even if it didn't error, the tags would not be relevant to the current project. In other words, this code either breaks or disrupts completion everywhere beyond the current haskell project. So, the correct solution here is to leave tags-table-list unchanged: users such as the author of 2b4e49c should instead use directory-local variables to set tags-table-list or tags-file-name locally to their haskell project.
gracjan
added a commit
that referenced
this pull request
Nov 2, 2015
Don't spuriously modify tags-table-list's global value
Sign up for free
to join this conversation on GitHub.
Already have an account?
Sign in to comment
Add this suggestion to a batch that can be applied as a single commit.
This suggestion is invalid because no changes were made to the code.
Suggestions cannot be applied while the pull request is closed.
Suggestions cannot be applied while viewing a subset of changes.
Only one suggestion per line can be applied in a batch.
Add this suggestion to a batch that can be applied as a single commit.
Applying suggestions on deleted lines is not supported.
You must change the existing code in this line in order to create a valid suggestion.
Outdated suggestions cannot be applied.
This suggestion has been applied or marked resolved.
Suggestions cannot be applied from pending reviews.
Suggestions cannot be applied on multi-line comments.
Suggestions cannot be applied while the pull request is queued to merge.
Suggestion cannot be applied right now. Please check back later.
As part of #592, commit 2b4e49c modified this code to alter the global
value of tags-table-list as a side-effect, but this change was incorrect
and causes problems elsewhere.
Specifically, consider the following scenario:
haskell-mode-jump-to-tag
This results in a call to haskell-process-generate-tags, which tries to
run hasktags, whether or not it is installed. As a side effect, the
global value of tags-table-list is set to include
"/project/root/dir/TAGS", which was probably not even created
properly (most people won't have hasktags installed).
Then, imagine we're working in an unrelated project, and use Emacs'
built-in completion-at-point functionality (or company-mode, which wraps
it). Now, the tags-completion-at-point-function (enabled by default)
sees and uses the modified value of tags-table-list, and errors noisily
when called because that file does not exist. And even if it didn't
error, the tags would not be relevant to the current project.
In other words, this code either breaks or disrupts completion
everywhere beyond the current haskell project.
So, the correct solution here is to leave tags-table-list unchanged:
users such as the author of 2b4e49c should instead use directory-local
variables to set tags-table-list or tags-file-name locally to their
haskell project.