Posts tagged "emacs":

21 Mar 2021

Todo items in org-roam, an update

I got an email from Mr Z with a nice modification to the code in my post on keeping todo items in org-roam.

He already had a bunch of agenda files that he wanted to keep using (I had so few of them that I'd simply converted them to roam files). Here's the solution he shared with me:

(defvar roam-extra-original-org-agenda-files nil
  "Original value of  `org-agenda-files'.")

(defun roam-extra:update-todo-files (&rest _)
  "Update the value of `org-agenda-files'."
  (unless roam-extra-original-org-agenda-files
    (setq roam-extra-original-org-agenda-files org-agenda-files))
  (setq org-agenda-files
        (append roam-extra-original-org-agenda-files
                (roam-extra:todo-files))))

It's a rather nice modification I think. Thanks to Mr Z for agreeing to let me share it here.

Tags: emacs org-mode org-roam
14 Mar 2021

Keeping todo items in org-roam

A while ago I made an attempt to improve my work habits by keeping a document with TODO items. It lasted only for a while, and I've since had the intention to make another attempt. Since then I've started using org-roam and I've managed to create a habit of writing daily journal notes using org-roam's daily-notes. A few times I've thought that it might fit me well to put TODO items in the notes, but that would mean that I'd have to somehow keep track of them. At first I manually added a tag to each journal fily containing a TODO item. That didn't work very well at all, which should have been obvious up front. Then I added the folders where I keep roam files and journals to org-agenda-files, that worked a lot better. I'd still be using that, even if I expected it to slow down considerably as the number of files grow, but then I found a post on dynamic and fast agenda with org-roam.

I adjusted it slightly to fit my own setup a bit better, i.e. I made a Spacemacs layer, roam-extra, I use the tag todo, and I use a different hook to get the tag added on opening an org-roam file.

The layer consists of a single file, layers/roam-extra/funcs.el. In it I define 4 functions (they are pretty much copies of the functions in the post linked above):

  1. roam-extra:todo-p - returns non-nil if the current current buffer contains a TODO item.
  2. roam-extra:update-todo-tag - updates the tags of the current buffer to reflect the presence of TODO items, i.e. ensure the the tag todo is present iff there's a TODO item.
  3. roam-extra:todo-files - uses the org-roam DB to return a list of all files containing the tag todo.
  4. roam-extra:update-todo-files - adjusts 'org-agenda-files to contain only the files with TODO items.

I've put the full contents of the file at the end of the post.

To ensure that the todo tag is correct in all org-mode files I've added roam-extra:update-todo-tag to hooks that are invoked on opening an org-ram file and when saving a file. (I would love to find a more specialise hook than before-save-hook, but it works for now.)

(add-hook 'org-roam-file-setup-hook #'roam-extra:update-todo-tag)
(add-hook 'before-save-hook #'roam-extra:update-todo-tag)

To ensure that the list of files with TODO items is kept up to date when I open I also wrap org-agenda in an advice so roam-extra:update-todo-files is called prior to the agenda being opened.

(advice-add 'org-agenda :before #'roam-extra:update-todo-files)

The layer, layers/roam-extra/funcs.el

(defun roam-extra:todo-p ()
  "Return non-nil if current buffer has any TODO entry.

TODO entries marked as done are ignored, meaning the this
function returns nil if current buffer contains only completed
tasks."
  (org-element-map
      (org-element-parse-buffer 'headline)
      'headline
    (lambda (h)
      (eq (org-element-property :todo-type h)
          'todo))
    nil 'first-match))

(defun roam-extra:update-todo-tag ()
  "Update TODO tag in the current buffer."
  (when (and (not (active-minibuffer-window))
             (org-roam--org-file-p buffer-file-name))
    (let* ((file (buffer-file-name (buffer-base-buffer)))
           (all-tags (org-roam--extract-tags file))
           (prop-tags (org-roam--extract-tags-prop file))
           (tags prop-tags))
      (if (roam-extra:todo-p)
          (setq tags (seq-uniq (cons "todo" tags)))
        (setq tags (remove "todo" tags)))
      (unless (equal prop-tags tags)
        (org-roam--set-global-prop
         "roam_tags"
         (combine-and-quote-strings tags))))))

(defun roam-extra:todo-files ()
  "Return a list of note files containing todo tag."
  (seq-map
   #'car
   (org-roam-db-query
    [:select file
             :from tags
             :where (like tags (quote "%\"todo\"%"))])))

(defun roam-extra:update-todo-files (&rest _)
  "Update the value of `org-agenda-files'."
  (setq org-agenda-files (roam-extra:todo-files)))
Tags: emacs org-mode org-roam spacemacs
05 Mar 2021

Flycheck and HLS

I've been using LSP for most programming languages for a while now. HLS is really very good now, but I've found that it doesn't warn on quite all things I'd like it to so I find myself having to swap between the 'lsp and 'haskell-ghc checkers. However, since flycheck supports chaining checkers I thought there must be a way to have both checkers active at the same time.

The naive approach didn't work due to load order of things in Spacemacs so I had to experiment a bit to find something that works.

The first issue was to make sure that HLS is available at all. I use shell.nix together with direnv extensively and I had noticed that lsp-mode tried to load HLS before direnv had put it in the $PATH. I think the 'lsp-beforeinitialize-hook is the hook to use for this:

(add-hook 'lsp-before-initialize-hook #'direnv-update-environment))

I made a several attempt to chain the checkers but kept on getting errors due to the 'lsp checker not being defined yet. Another problem I ran into was that the checkers were chained too late, resulting in having to manually run flycheck-buffer on the first file I opened. (Deferred loading is a brilliant thing, but make some things really difficult to debug.) After quite a bit of experimenting and reading the description of various hooks I did find something that works:

(with-eval-after-load 'lsp-mode
  (defun magthe:lsp-next-checker ()
    (flycheck-add-next-checker 'lsp '(warning . haskell-ghc)))
  (add-hook 'lsp-lsp-haskell-after-open-hook
            #'magthe:lsp-next-checker))

Of course I have no idea if this is the easiest or most elegant solution but it does work for my testcases:

  1. Open a file in a project, SPC p l - choose project - choose a Haskell file.
  2. Open a project, SPC p l followed by C-d, and then open a Haskell file.

Suggestions for improvements are more than welcome, of course.

Tags: emacs haskell flycheck
22 Jun 2020

Better Nix setup for Spacemacs

In an earlier post I documented my setup for getting Spacemacs/Emacs to work with Nix. I've since found a much more elegant solution based on

No more Emacs packages for Nix and no need to defining functions that wrap executables in an invocation of nix-shell.

There's a nice bonus too, with this setup I don't need to run nix-shell, which always drops me at a bash prompt, instead I get a working setup in my shell of choice.

Setting up direnv

The steps for setting up direnv depends a bit on your setup, but luckily I found the official instructions for installing direnv to be very clear and easy to follow. There's not much I can add to that.

Setting up Spacemacs

Since emacs-direnv isn't included by default in Spacemacs I needed to do a bit of setup. I opted to create a layer for it, rather than just drop it in the list dotspacemacs-additional-packages. Yes, a little more complicated, but not difficult and I nurture an intention of submitting the layer for inclusion in Spacemacs itself at some point. I'll see where that goes.

For now, I put the following in the file ~/.emacs.d/private/layers/direnv/packages.el:

(defconst direnv-packages
      '(direnv))

(defun direnv/init-direnv ()
  (use-package direnv
    :init
    (direnv-mode)))

Setting up the project folders

In each project folder I then add the file .envrc containing a single line:

use_nix

Then I either run direnv allow from the command line, or run the function direnv-allow after opening the folder in Emacs.

Using it

It's as simple as moving into the folder in a shell – all required envvars are set up on entry and unset on exit.

In Emacs it's just as simple, just open a file in a project and the envvars are set. When switching to a buffer outside the project the envvars are unset.

There is only one little caveat, nix-build doesn't work inside a Nix shell. I found out that running

IN_NIX_SHELL= nix-build

does work though.

Tags: emacs nix spacemacs
07 Dec 2019

Nix setup for Spacemacs

Edit 2020-06-22: I've since found a better setup for this.

When using ghcide and LSP, as I wrote about in my post on Haskell, ghcide, and Spacemacs, I found myself ending up recompiling a little too often. This pushed me to finally start looking at Nix. After a bit of a fight I managed to get ghcide from Nix, which brought me the issue of setting up Spacemacs. Inspired by a gist from Samuel Evans-Powell and a guide to setting up an environment for Reflex by Thales Macedo Garitezi I ended up with the following setup:

(defun dotspacemacs/layers ()
  (setq-default
   ...
   dotspacemacs-additional-packages
   '(
     nix-sandbox
     nix-haskell-mode
     ...
     )
   ...
   ))
(defun dotspacemacs/user-config ()
  ...
  (add-hook 'haskell-mode-hook #'lsp)
  (add-hook 'haskell-mode-hook 'nix-haskell-mode)
  (add-hook 'haskell-mode-hook
            (lambda ()
              (setq-local flycheck-executable-find
                          (lambda (cmd)
                            (nix-executable-find (nix-current-sandbox) cmd)))
              (setq-local flycheck-command-wrapper-function
                          (lambda (argv)
                            (apply 'nix-shell-command (nix-current-sandbox) argv)))
              (setq-local haskell-process-wrapper-function
                          (lambda (argv)
                            (apply 'nix-shell-command (nix-current-sandbox) argv)))
              (setq-local lsp-haskell-process-wrapper-function
                          (lambda (argv)
                            `("nix-shell" "-I" "." "--command" "ghcide --lsp" ,(nix-current-sandbox))))))
  (add-hook 'haskell-mode-hook
            (lambda ()
              (flycheck-add-next-checker 'lsp-ui '(warning . haskell-stack-ghc))))
  ...
  )

It seems to work, but please let me know if you have suggestions for improvements.

Tags: emacs nix spacemacs
05 Nov 2019

Populating Projectile's cache

As I track the develop branch of Spacemacs I occasionally clean out my cache of projects known to Projectile. Every time it takes a while before I'm back at a stage where I very rarely have to visit something that isn't already in the cache.

However, today I found the function projectile-add-known-project, which prompted me to write the following function that'll help me quickly re-building the cache the next time I need to reset Spacemacs to a known state again.

(defun projectile-extra-add-projects-in-subfolders (projects-root)
  (interactive (list (read-directory-name "Add to known projects: ")))
  (message "Searching for projects in %s..." projects-root)
  (let ((dirs (seq-map 'file-name-directory (directory-files-recursively projects-root "^.git$" t))))
    (seq-do 'projectile-add-known-project dirs)
    (message "Added %d projects" (length dirs))))
Tags: emacs elisp
20 Oct 2019

Ditaa in Org mode

Just found out that Emacs ships with Babel support for ditaa (yes, I'm late to the party).

Sweet! That is yet another argument for converting all our README.md into README.org at work.

giphy.gif\

The changes I made to my Spacemacs config are

(defun dotspacemacs/user-config ()
  ...
  (with-eval-after-load 'org
    ...
    (add-to-list 'org-babel-load-languages '(ditaa . t))
    (setq org-ditaa-jar-path "/usr/share/java/ditaa/ditaa-0.11.jar"))
  ...)
Tags: emacs org-mode
19 Sep 2019

Haskell, ghcide, and Spacemacs

The other day I read Chris Penner's post on Haskell IDE Support and thought I'd make an attempt to use it with Spacemacs.

After running stack build hie-bios ghcide haskell-lsp --copy-compiler-tool I had a look at the instructions on using haskell-ide-engine with Spacemacs. After a bit of trial and error I came up with these changes to my ~/.spacemacs:

(defun dotspacemacs/layers ()
  (setq-default
   dotspacemacs-configuration-layers
   '(
    ...
    lsp
    (haskell :variables
             haskell-completion-backend 'lsp
             )
    ...)
  )
)
(defun dotspacemacs/user-config ()
  (setq lsp-haskell-process-args-hie '("exec" "ghcide" "--" "--lsp")
        lsp-haskell-process-path-hie "stack"
        lsp-haskell-process-wrapper-function (lambda (argv) (cons (car argv) (cddr argv)))
        )
  (add-hook 'haskell-mode-hook
            #'lsp))

The slightly weird looking lsp-haskell-process-wrapper-function is removing the pesky --lsp inserted by this line.

That seems to work. Though I have to say I'm not ready to switch from intero just yet. Two things in particular didn't work with =ghcide=/LSP:

  1. Switching from one the Main.hs in one executable to the Main.hs of another executable in the same project didn't work as expected – I had hints and types in the first, but nothing in the second.
  2. Jump to the definition of a function defined in the package didn't work – I'm not willing to use GNU GLOBAL or some other source tagging system.
Tags: emacs haskell lsp spacemacs
07 May 2019

Some OrgMode stuff

The last few days I've watched Rainer K├Ânig's OrgMode videos. It's resulted in a few new settings that makes Org a little more useful.

Variable Value Description
calendar-week-start-day 1 Weeks start on Monday!
org-modules (list) org-habit Support for tracking habits
org-modules (list) org-id Improved support for ID property
org-agenda-start-on-weekday 1 Weeks start on Monday, again!
org-log-into-drawer t Put notes (logs) into a drawer
org-enforce-todo-checkbox-dependencies t Checkboxes must be checked before a TODO can become DONE
org-id-link-to-org-use-id t Prefer use of ID property for links
Tags: emacs org-mode
16 Mar 2019

TIL: prompt matters to org-mode

A workmate just embellished some shell code blocks I'd put in a shared org-mode file with :session s. When I tried to run the blocks with sessions my emacs just froze up though. I found a post on the emacs StackExchange that offered a possible cause for it: the prompt.

I'm using bash-it so my prompt is rather far from the default.

After inspecting the session buffer simply added the following to my ~/.bashrc

if [[ ${TERM} == "dumb" ]]; then
    export BASH_IT_THEME='standard'
else
    export BASH_IT_THEME='simple'
fi

and now I can finally run shell code blocks in sessions.

Tags: emacs org-mode
28 Jan 2019

A missing piece in my Emacs/Spacemacs setup for Haskell development

With the help of a work mate I've finally found this gem that's been missing from my Spacemacs setup

(with-eval-after-load 'intero
  (flycheck-add-next-checker 'intero '(warning . haskell-hlint))
  (flycheck-add-next-checker 'intero '(warning . haskell-stack-ghc)))
Tags: haskell emacs spacemacs
14 Jul 2018

QuickCheck on a REST API

Since I'm working with web stuff nowadays I thought I'd play a little with translating my old post on using QuickCheck to test C APIs to the web.

The goal and how to reach it

I want to use QuickCheck to test a REST API, just like in the case of the C API the idea is to

  1. generate a sequence of API calls (a program), then
  2. run the sequence against a model, as well as
  3. run the sequence against the web service, and finally
  4. compare the resulting model against reality.

The REST API

I'll use a small web service I'm working on, and then concentrate on only a small part of the API to begin with.

The parts of the API I'll use for the programs at this stage are

Method Route Example in Example out
POST /users {"userId": 0, "userName": "Yogi Berra"} {"userId": 42, "userName": "Yogi Berra"}
DELETE /users/:id    

The following API calls will also be used, but not in the programs

Method Route Example in Example out
GET /users   [0,3,7]
GET /users/:id   {"userId": 42, "userName": "Yogi Berra"}
POST /reset    

Representing API calls

Given the information about the API above it seems the following is enough to represent the two calls of interest together with a constructor representing the end of a program

data ApiCall = AddUser Text
             | DeleteUser Int
             | EndProgram
             deriving (Show)

and a program is just a sequence of calls, so list of ApiCall will do. However, since I want to generate sequences of calls, i.e. implement Arbitrary, I'll wrap it in a newtype

newtype Program = Prog [ApiCall]

Running against a model (simulation)

First of all I need to decide what model to use. Based on the part of the API I'm using I'll use an ordinary dictionary of Int and Text

type Model = M.Map Int Text

Simulating execution of a program is simulating each call against a model that's updated with each step. I expect the final model to correspond to the state of the real service after the program is run for real. The simulation begins with an empty dictionary.

simulateProgram :: Program -> Model
simulateProgram (Prog cs) = foldl simulateCall M.empty cs

The simulation of the API calls must then be a function taking a model and a call, returning an updated model

simulateCall :: Model -> ApiCall -> Model
simulateCall m (AddUser t) = M.insert k t m
  where
    k = succ $ foldl max 0 (M.keys m)
simulateCall m (DeleteUser k) = M.delete k m
simulateCall m EndProgram = m

Here I have to make a few assumptions. First, I assume the indeces for the users start on 1. Second, that the next index used always is the successor of highest currently used index. We'll see how well this holds up to reality later on.

Running against the web service

Running the program against the actual web service follows the same pattern, but here I'm dealing with the real world, so it's a little more messy, i.e. IO is involved. First the running of a single call

runCall :: Manager -> ApiCall -> IO ()
runCall mgr (AddUser t) = do
  ireq <- parseRequest "POST http://localhost:3000/users"
  let req = ireq { requestBody = RequestBodyLBS (encode $ User 0 t)}
  resp <- httpLbs req mgr
  guard (status201 == responseStatus resp)

runCall mgr (DeleteUser k) = do
  req <- parseRequest $ "DELETE http://localhost:3000/users/" ++ show k
  resp <- httpNoBody req mgr
  guard (status200 == responseStatus resp)

runCall _ EndProgram = return ()

The running of a program is slightly more involved. Of course I have to set up the Manager needed for the HTTP calls, but I also need to

  1. ensure that the web service is in a well-known state before starting, and
  2. extract the state of the web service after running the program, so I can compare it to the model
runProgram :: Program -> IO Model
runProgram (Prog cs) = do
  mgr <- newManager defaultManagerSettings
  resetReq <- parseRequest "POST http://localhost:3000/reset"
  httpNoBody resetReq mgr
  mapM_ (runCall mgr) cs
  model <- extractModel mgr
  return model

The call to POST /reset resets the web service. I would have liked to simply restart the service completely, but I failed in automating it. I think I'll have to take a closer look at the implementation of scotty to find a way.

Extracting the web service state and packaging it in a Model is a matter of calling GET /users and then repeatedly calling GET /users/:id with each id gotten from the first call

extractModel :: Manager -> IO Model
extractModel mgr = do
  req <- parseRequest "http://localhost:3000/users"
  resp <- httpLbs req mgr
  let (Just ids) = decode (responseBody resp) :: Maybe [Int]
  users <- forM ids $ \ id -> do
    req <- parseRequest $ "http://localhost:3000/users/" ++ show id
    resp <- httpLbs req mgr
    let (Just (user:_)) = decode (responseBody resp) :: Maybe [User]
    return user
  return $ foldl (\ map (User id name) -> M.insert id name map) M.empty users

Generating programs

My approach to generating a program is based on the idea that given a certain state there is only a limited number of possible calls that make sense. Given a model m it makes sense to make one of the following calls:

  • add a new user
  • delete an existing user
  • end the program

Based on this writing genProgram is rather straight forward

genProgram :: Gen Program
genProgram = Prog <$> go M.empty
  where
    possibleAddUser _ = [AddUser <$> arbitrary]
    possibleDeleteUser m = map (return . DeleteUser) (M.keys m)
    possibleEndProgram _ = [return EndProgram]

    go m = do
      let possibles = possibleDeleteUser m ++ possibleAddUser m ++ possibleEndProgram m
      s <- oneof possibles
      let m' = simulateCall m s
      case s of
        EndProgram -> return []
        _ -> (s:) <$> go m'

Armed with that the Arbitrary instance for Program can be implemented as1

instance Arbitrary Program where
  arbitrary = genProgram
  shrink p = []

The property of an API

The steps in the first section can be used as a recipe for writing the property

prop_progCorrectness :: Program -> Property
prop_progCorrectness program = monadicIO $ do
  let simulatedModel = simulateProgram program
  runModel <- run $ runProgram program
  assert $ simulatedModel == runModel

What next?

There are some improvements that I'd like to make:

  • Make the generation of Program better in the sense that the programs become longer. I think this is important as I start tackling larger APIs.
  • Write an implementation of shrink for Program. With longer programs it's of course more important to actually implement shrink.

I'd love to hear if others are using QuickCheck to test REST APIs in some way, if anyone has suggestions for improvements, and of course ideas for how to implement shrink in a nice way.

Footnotes:

1

Yes, I completely skip the issue of shrinking programs at this point. This is OK at this point though, because the generated =Programs=s do end up to be very short indeed.

Tags: emacs haskell flycheck
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