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ob-elixir/tasks/02-basic-execution.md

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# Task 02: Basic Code Execution
**Phase**: 1 - Core (MVP)
**Priority**: Critical
**Estimated Time**: 1-2 hours
**Dependencies**: Task 01 (Project Setup)
## Objective
Implement the core `org-babel-execute:elixir` function that can execute Elixir code blocks using external process (one-shot execution).
## Prerequisites
- Task 01 completed
- Elixir installed and accessible via `elixir` command
## Steps
### Step 1: Add customization group and variables
Add to `ob-elixir.el`:
```elisp
;;; Customization
(defgroup ob-elixir nil
"Org Babel support for Elixir."
:group 'org-babel
:prefix "ob-elixir-")
(defcustom ob-elixir-command "elixir"
"Command to execute Elixir code.
Can be a full path or command name if in PATH."
:type 'string
:group 'ob-elixir
:safe #'stringp)
```
### Step 2: Add default header arguments
```elisp
;;; Header Arguments
(defvar org-babel-default-header-args:elixir
'((:results . "value")
(:session . "none"))
"Default header arguments for Elixir code blocks.")
```
### Step 3: Register the language
```elisp
;;; Language Registration
;; File extension for tangling
(add-to-list 'org-babel-tangle-lang-exts '("elixir" . "ex"))
;; Associate with elixir-mode for syntax highlighting (if available)
(with-eval-after-load 'org-src
(add-to-list 'org-src-lang-modes '("elixir" . elixir)))
```
### Step 4: Implement the execute function
```elisp
;;; Execution
(defun org-babel-execute:elixir (body params)
"Execute a block of Elixir code with org-babel.
BODY is the Elixir code to execute.
PARAMS is an alist of header arguments.
This function is called by `org-babel-execute-src-block'."
(let* ((result-type (cdr (assq :result-type params)))
(result-params (cdr (assq :result-params params)))
(result (ob-elixir--execute body result-type)))
(org-babel-reassemble-table
(org-babel-result-cond result-params
result
(org-babel-script-escape result))
(org-babel-pick-name (cdr (assq :colname-names params))
(cdr (assq :colnames params)))
(org-babel-pick-name (cdr (assq :rowname-names params))
(cdr (assq :rownames params))))))
```
### Step 5: Implement the internal execute function
```elisp
(defun ob-elixir--execute (body result-type)
"Execute BODY as Elixir code.
RESULT-TYPE is either `value' or `output'.
For `value', wraps code to capture return value.
For `output', captures stdout directly.
Returns the result as a string."
(let* ((tmp-file (org-babel-temp-file "ob-elixir-" ".exs"))
(code (if (eq result-type 'value)
(ob-elixir--wrap-for-value body)
body)))
(with-temp-file tmp-file
(insert code))
(let ((result (org-babel-eval
(format "%s %s"
ob-elixir-command
(org-babel-process-file-name tmp-file))
"")))
(string-trim result))))
```
### Step 6: Implement the value wrapper
```elisp
(defconst ob-elixir--value-wrapper
"result = (
%s
)
IO.puts(inspect(result, limit: :infinity, printable_limit: :infinity, charlists: :as_lists))
"
"Wrapper template for capturing Elixir expression value.
%s is replaced with the user's code.")
(defun ob-elixir--wrap-for-value (body)
"Wrap BODY to capture its return value.
The wrapper evaluates BODY, then prints the result using
`inspect/2` with infinite limits to avoid truncation."
(format ob-elixir--value-wrapper body))
```
### Step 7: Add tests
Add to `test/test-ob-elixir.el`:
```elisp
(ert-deftest ob-elixir-test-elixir-available ()
"Test that Elixir is available."
(should (executable-find ob-elixir-command)))
(ert-deftest ob-elixir-test-simple-value ()
"Test simple value evaluation."
(skip-unless (executable-find ob-elixir-command))
(let ((result (ob-elixir--execute "1 + 1" 'value)))
(should (equal "2" result))))
(ert-deftest ob-elixir-test-simple-output ()
"Test simple output evaluation."
(skip-unless (executable-find ob-elixir-command))
(let ((result (ob-elixir--execute "IO.puts(\"hello\")" 'output)))
(should (equal "hello" result))))
(ert-deftest ob-elixir-test-multiline-value ()
"Test multiline code value evaluation."
(skip-unless (executable-find ob-elixir-command))
(let ((result (ob-elixir--execute "x = 10\ny = 20\nx + y" 'value)))
(should (equal "30" result))))
(ert-deftest ob-elixir-test-list-result ()
"Test list result."
(skip-unless (executable-find ob-elixir-command))
(let ((result (ob-elixir--execute "[1, 2, 3]" 'value)))
(should (equal "[1, 2, 3]" result))))
(ert-deftest ob-elixir-test-map-result ()
"Test map result."
(skip-unless (executable-find ob-elixir-command))
(let ((result (ob-elixir--execute "%{a: 1, b: 2}" 'value)))
(should (string-match-p "%{a: 1, b: 2}" result))))
```
### Step 8: Test in an org buffer
Create a test org file `test.org`:
```org
* Test ob-elixir
** Basic arithmetic (value)
#+BEGIN_SRC elixir
1 + 1
#+END_SRC
** Output test
#+BEGIN_SRC elixir :results output
IO.puts("Hello, World!")
#+END_SRC
** List manipulation
#+BEGIN_SRC elixir
Enum.map([1, 2, 3], fn x -> x * 2 end)
#+END_SRC
```
Press `C-c C-c` on each block to test.
## Acceptance Criteria
- [ ] `org-babel-execute:elixir` function exists
- [ ] Simple expressions evaluate correctly: `1 + 1` returns `2`
- [ ] `:results value` captures return value (default)
- [ ] `:results output` captures stdout
- [ ] Multiline code executes correctly
- [ ] Lists and maps are returned in Elixir format
- [ ] All tests pass: `make test`
## Troubleshooting
### "Cannot find elixir"
Ensure Elixir is in PATH:
```bash
which elixir
elixir --version
```
Or set the full path:
```elisp
(setq ob-elixir-command "/usr/local/bin/elixir")
```
### Results are truncated
The wrapper uses `limit: :infinity` to prevent truncation. If still truncated, check for very large outputs.
### ANSI codes in output
We'll handle this in a later task. For now, output should be clean with the current approach.
## Files Modified
- `ob-elixir.el` - Add execution functions
- `test/test-ob-elixir.el` - Add execution tests
## References
- [docs/03-org-babel-implementation-guide.md](../docs/03-org-babel-implementation-guide.md)
- [docs/04-elixir-integration-strategies.md](../docs/04-elixir-integration-strategies.md)