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tasks/11-fix-error-display-in-buffer.md

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+# Task 11: Fix Exception Display in Org Buffer
+
+## Problem
+
+When an Elixir code block throws an exception, the error is not displayed in the org buffer. The error is only shown in the minibuffer/messages, leaving the user without visible feedback in their document.
+
+### Root Cause
+
+1. The variable `ob-elixir-signal-errors` defaults to `t` (line 57-63 in `ob-elixir.el`)
+2. When an error is detected, `ob-elixir--process-result` (line 206-222) calls `signal`, which throws an Emacs error
+3. The signaled error propagates up and prevents `org-babel-execute:elixir` from returning a result
+4. Since no result is returned, org-babel has nothing to insert into the buffer
+
+### Current Behavior
+
+| `ob-elixir-signal-errors` | What happens |
+|--------------------------|--------------|
+| `t` (default) | Error is signaled, shown in minibuffer, **NOT inserted in buffer** |
+| `nil` | Error is returned as the result string, **inserted in buffer** |
+
+### Desired Behavior
+
+Errors should always be displayed in the org buffer as the result, regardless of the `ob-elixir-signal-errors` setting.
+
+## Scope
+
+- Non-session execution mode only
+- Session mode is out of scope for this fix
+
+## Implementation Plan
+
+### Step 1: Modify `ob-elixir--process-result` to pass full error output
+
+**File:** `ob-elixir.el` (line 218)
+
+**Change:** When signaling an error, pass the full error output instead of the formatted short message.
+
+**Current code (line 218):**
+```elisp
+(list (ob-elixir--format-error error-info)))
+```
+
+**Proposed change:**
+```elisp
+(list (plist-get error-info :full-output)))
+```
+
+**Rationale:**
+- The `:full-output` field contains the complete multi-line error output including stack traces
+- This ensures the `condition-case` in `org-babel-execute:elixir` returns the same full output that would be returned when `ob-elixir-signal-errors` is `nil`
+- The formatted short message from `ob-elixir--format-error` only includes the exception name and first-line message, which is insufficient for debugging
+
+### Step 2: Wrap result computation in `org-babel-execute:elixir` (ALREADY DONE)
+
+**File:** `ob-elixir.el` (lines 928-945)
+
+**Status:** This step was already implemented. The `condition-case` wraps the result computation and catches `ob-elixir-error`, returning `(cadr err)` which will now contain the full error output after Step 1 is applied.
+
+```elisp
+(result (condition-case err
+            (cond
+             ;; Session mode with deps
+             ((and session (not (string= session "none")) deps-string)
+              (ob-elixir--evaluate-in-session-with-deps
+               session full-body result-type deps-string))
+             ;; Session mode without deps
+             ((and session (not (string= session "none")))
+              (ob-elixir--evaluate-in-session session full-body result-type))
+             ;; Non-session with deps
+             (deps-string
+              (ob-elixir--execute-with-deps full-body result-type deps-string))
+             ;; Plain execution
+             (t
+              (ob-elixir--execute full-body result-type)))
+          (ob-elixir-error
+           ;; Return error message so it appears in buffer
+           (cadr err))))
+```
+
+### Step 3: Add tests for the new behavior
+
+**File:** `test/test-ob-elixir-errors.el`
+
+**Add new test:** Verify that errors appear in org buffer output when `ob-elixir-signal-errors` is `t`.
+
+```elisp
+(ert-deftest ob-elixir-test-error-appears-in-result ()
+  "Test that errors appear in result even when signaling is enabled."
+  (skip-unless (executable-find ob-elixir-command))
+  (let ((ob-elixir-signal-errors t))
+    ;; Execute via the main entry point (not ob-elixir--execute directly)
+    (let ((result (org-babel-execute:elixir "raise \"test error\"" 
+                                            '((:result-type . value)
+                                              (:result-params . ("replace"))))))
+      ;; Result should contain the error, not be nil/empty
+      (should result)
+      (should (string-match-p "RuntimeError" result)))))
+```
+
+**Rationale:** The existing test `ob-elixir-test-error-signaling` tests that `ob-elixir--execute` signals an error, but doesn't test the full flow through `org-babel-execute:elixir`. The new test verifies the end-to-end behavior.
+
+### Step 4: Update TODO.org
+
+**File:** `TODO.org`
+
+**Change:** Mark the first item ("errors should be printed in the org buffer") as DONE.
+
+## Summary of Changes
+
+| File | Change |
+|------|--------|
+| `ob-elixir.el` | Change signal data to pass `:full-output` instead of formatted message |
+| `ob-elixir.el` | Wrap result computation in `condition-case` to catch `ob-elixir-error` (already done) |
+| `test/test-ob-elixir-errors.el` | Add test for error display in org buffer |
+| `TODO.org` | Mark issue as resolved |
+
+## Files NOT Modified
+
+- Session-related code
+- `ob-elixir--process-result` (keeps existing signaling behavior)
+- `ob-elixir-signal-errors` default value (stays `t`)
+
+## Verification
+
+After implementation, test with:
+
+```org
+#+begin_src elixir
+raise "This error should appear in the buffer"
+#+end_src
+```
+
+Expected: The RuntimeError message should appear as the result block below the code block.