Feat: Add more emacs mcps: buffer and project query tools and xref support by tninja · Pull Request #277 · tninja/ai-code-interface.el

tninja · 2026-04-05T01:12:00Z

Referencing https://github.com/acmorrow/claude-code-ide-extras, port 4 mcps from there.

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chatgpt-codex-connector · 2026-04-05T01:15:25Z

+         (group (ai-code-mcp--display-path
+                 (xref-location-group location)))


Preserve full paths for external xref hits

Wrapping xref-location-group with ai-code-mcp--display-path truncates any location outside the active project to file-name-nondirectory, so references/definitions from different external files with the same basename become indistinguishable (for example, two different index.js files). Before this change, the formatter kept the full group path, so this is a regression in result accuracy whenever the backend returns matches outside the project root.

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Pull request overview

Adds additional MCP tools to ai-code-mcp-server.el to expose more Emacs editor/project navigation capabilities (ported from claude-code-ide-extras), plus accompanying ERT coverage.

Changes:

Add MCP tools for buffer line-range querying, project file listing, and project buffer listing.
Add MCP tool to find xref definitions at a specific file location (line/column).
Extend ERT tests to cover the new tools and ensure they appear in the tools list.

Reviewed changes

Copilot reviewed 3 out of 3 changed files in this pull request and generated 6 comments.

File	Description
`ai-code-mcp-server.el`	Registers new MCP tools and implements buffer/project/xref helpers, plus tweaks xref formatting and result formatting.
`test/test_ai-code-mcp-server.el`	Updates tool-list expectations and adds tests for the new MCP tools.

Copilot · 2026-04-05T01:16:17Z

@@ -14,6 +14,7 @@
 (require 'cl-lib)
 (require 'imenu)
 (require 'project)


ai-code-mcp-server.el uses several seq-* functions (e.g., seq-remove, seq-filter) but does not (require 'seq). Many other modules in this repo explicitly require seq when using these functions; adding the require here avoids load-order dependent runtime failures and byte-compile warnings when this file is loaded standalone.

Suggested change

(require 'project)

(require 'project)

(require 'seq)

Copilot · 2026-04-05T01:16:17Z

+              (string-trim-right
+               (buffer-substring-no-properties start-pos (point))))))))))


ai-code-mcp-buffer-query uses string-trim-right on the extracted substring. This will strip all trailing whitespace from the last returned line (not just the final newline), which can corrupt code/text where trailing spaces are significant. Prefer only removing a single trailing newline (or return the exact substring unchanged) to preserve buffer contents faithfully.

Suggested change

(string-trim-right

(buffer-substring-no-properties start-pos (point))))))))))

(let ((text (buffer-substring-no-properties start-pos (point))))

(if (string-suffix-p "\n" text)

(substring text 0 -1)

text)))))))))

Copilot · 2026-04-05T01:16:17Z

+      (when (or (and start-line (not num-lines))
+                (and num-lines (not start-line)))
+        (error "Arguments start_line and num_lines must both be provided or both be omitted"))
+      (with-current-buffer buffer
+        (save-excursion
+          (if (not start-line)
+              (buffer-substring-no-properties (point-min) (point-max))
+            (goto-char (point-min))
+            (forward-line (1- start-line))
+            (let ((start-pos (point)))
+              (forward-line num-lines)


ai-code-mcp-buffer-query claims start_line is 1-based, but it doesn’t validate start_line >= 1 and num_lines >= 1. Passing 0/negative values will produce surprising results (or errors) due to (forward-line (1- start-line)) / (forward-line num-lines). Add explicit validation with a clear error message (or normalize inputs) before moving point.

Copilot · 2026-04-05T01:16:17Z

+(defun ai-code-mcp-get-project-files ()
+  "Return regular files in the current project as relative paths."
+  (let ((project-dir (ai-code-mcp--project-directory)))
+    (if (not (and project-dir (file-directory-p project-dir)))
+        nil
+      (mapcar #'ai-code-mcp--display-path
+              (seq-filter
+               #'file-regular-p
+               (directory-files-recursively project-dir ".*" t))))))


ai-code-mcp-get-project-files walks the entire project directory via directory-files-recursively ".*", which will include files like .git/* and can be very slow on large repos. Prefer project-current + project-files (with a recursive fallback like ai-code-session-link--project-files uses) so the result respects project backends/ignores and avoids scanning VCS internals.

Suggested change

(defun ai-code-mcp-get-project-files ()

"Return regular files in the current project as relative paths."

(let ((project-dir (ai-code-mcp--project-directory)))

(if (not (and project-dir (file-directory-p project-dir)))

nil

(mapcar #'ai-code-mcp--display-path

(seq-filter

#'file-regular-p

(directory-files-recursively project-dir ".*" t))))))

(defun ai-code-mcp--project-files (project-dir)

"Return regular files for PROJECT-DIR using project APIs when available.

Fall back to a recursive directory walk that skips VCS internals."

(let* ((default-directory (file-name-as-directory project-dir))

(project (project-current nil))

(project-root default-directory))

(cond

((and project (fboundp 'project-files))

(seq-filter

#'file-regular-p

(mapcar (lambda (file)

(if (file-name-absolute-p file)

file

(expand-file-name file project-root)))

(project-files project))))

(t

(cl-labels

((collect-files (dir)

(apply

#'append

(mapcar

(lambda (entry)

(cond

((member entry '("." "..")) nil)

((string-prefix-p "." entry) nil)

(t

(let ((path (expand-file-name entry dir)))

(cond

((file-directory-p path)

(collect-files path))

((file-regular-p path)

(list path))

(t nil))))))

(directory-files dir nil nil t))))

(collect-files project-root))))))

(defun ai-code-mcp-get-project-files ()

"Return regular files in the current project as relative paths."

(let ((project-dir (ai-code-mcp--project-directory)))

(if (not (and project-dir (file-directory-p project-dir)))

nil

(mapcar #'ai-code-mcp--display-path

(ai-code-mcp--project-files project-dir)))))

Copilot · 2026-04-05T01:16:18Z

 (defun ai-code-mcp--format-xref-item (item)
  "Return a human-readable line for xref ITEM."
  (let* ((location (xref-item-location item))
-         (group (xref-location-group location))
+         (group (ai-code-mcp--display-path
+                 (xref-location-group location)))
         (marker (xref-location-marker location))


ai-code-mcp--format-xref-item now runs xref-location-group through ai-code-mcp--display-path, but ai-code-mcp--display-path uses a simple string-prefix-p check against project-dir. That can misclassify paths like /tmp/proj2/... as being under /tmp/proj and produce misleading relative paths with ... Consider switching the containment check to file-in-directory-p (or ensure project-dir is normalized with a trailing slash) before calling file-relative-name.

Copilot · 2026-04-05T01:16:18Z

+(ert-deftest ai-code-test-mcp-xref-find-definitions-at-point-uses-location-context ()
+  "Definitions-at-point should resolve via the xref backend at a file location."
+  (let* ((project-dir (make-temp-file "ai-code-mcp-xref-defs-" t))
+         (file-path (expand-file-name "defs.el" project-dir))
+         (buffer (generate-new-buffer " *ai-code-mcp-xref-defs*")))
+    (unwind-protect
+        (progn
+          (with-temp-file file-path
+            (insert "(defun alpha ()\n")
+            (insert "  (beta))\n\n")
+            (insert "(defun beta ()\n")
+            (insert "  t)\n"))
+          (cl-letf (((symbol-function 'xref-find-backend)
+                     (lambda () 'mock-backend))
+                    ((symbol-function 'xref-backend-identifier-at-point)
+                     (lambda (_backend) "beta"))
+                    ((symbol-function 'xref-backend-definitions)
+                     (lambda (_backend identifier)
+                       (list (xref-make
+                              (format "%s definition" identifier)
+                              (xref-make-file-location file-path 4 0))))))
+            (should (equal '("defs.el:4: beta definition")
+                           (ai-code-mcp-xref-find-definitions-at-point
+                            file-path
+                            2
+                            3)))))
+      (when (buffer-live-p buffer)
+        (kill-buffer buffer))
+      (delete-directory project-dir t))))


In ai-code-test-mcp-xref-find-definitions-at-point-uses-location-context, the local buffer created with generate-new-buffer is never used, while the file-visiting buffer created by ai-code-mcp-xref-find-definitions-at-point (via find-file-noselect) is not cleaned up. This can leak buffers across the test suite; remove the unused buffer and explicitly kill the file-visiting buffer (or bind/kill it via ai-code-mcp--file-buffer).

tninja · 2026-04-05T02:37:01Z

feedbacks are addressed.

tninja added 2 commits April 4, 2026 18:09

Add buffer and project query tools and xref support

f0a711a

update author

5aa52ba

tninja requested a review from Copilot April 5, 2026 01:12

Copilot started reviewing on behalf of tninja April 5, 2026 01:12 View session

add README

e05e76b

chatgpt-codex-connector Bot reviewed Apr 5, 2026

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tninja added 2 commits April 4, 2026 18:23

add screenshot

e3ebf63

addressing feedbacks

09975c3

add HISTORY

12492b0

tninja merged commit 48d0a97 into main Apr 5, 2026
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Feat: Add more emacs mcps: buffer and project query tools and xref support#277

Feat: Add more emacs mcps: buffer and project query tools and xref support#277
tninja merged 6 commits intomainfrom
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		(group (ai-code-mcp--display-path
		(xref-location-group location)))

		(string-trim-right
		(buffer-substring-no-properties start-pos (point))))))))))

-              (string-trim-right
-               (buffer-substring-no-properties start-pos (point))))))))))
+              (let ((text (buffer-substring-no-properties start-pos (point))))
+                (if (string-suffix-p "\n" text)
+                    (substring text 0 -1)
+                  text)))))))))

-(defun ai-code-mcp-get-project-files ()
-  "Return regular files in the current project as relative paths."
-  (let ((project-dir (ai-code-mcp--project-directory)))
-    (if (not (and project-dir (file-directory-p project-dir)))
-        nil
-      (mapcar #'ai-code-mcp--display-path
-              (seq-filter
-               #'file-regular-p
-               (directory-files-recursively project-dir ".*" t))))))
+(defun ai-code-mcp--project-files (project-dir)
+  "Return regular files for PROJECT-DIR using project APIs when available.
+Fall back to a recursive directory walk that skips VCS internals."
+  (let* ((default-directory (file-name-as-directory project-dir))
+         (project (project-current nil))
+         (project-root default-directory))
+    (cond
+     ((and project (fboundp 'project-files))
+      (seq-filter
+       #'file-regular-p
+       (mapcar (lambda (file)
+                 (if (file-name-absolute-p file)
+                     file
+                   (expand-file-name file project-root)))
+               (project-files project))))
+     (t
+      (cl-labels
+          ((collect-files (dir)
+             (apply
+              #'append
+              (mapcar
+               (lambda (entry)
+                 (cond
+                  ((member entry '("." "..")) nil)
+                  ((string-prefix-p "." entry) nil)
+                  (t
+                   (let ((path (expand-file-name entry dir)))
+                     (cond
+                      ((file-directory-p path)
+                       (collect-files path))
+                      ((file-regular-p path)
+                       (list path))
+                      (t nil))))))
+               (directory-files dir nil nil t))))
+        (collect-files project-root))))))
+(defun ai-code-mcp-get-project-files ()
+  "Return regular files in the current project as relative paths."
+  (let ((project-dir (ai-code-mcp--project-directory)))
+    (if (not (and project-dir (file-directory-p project-dir)))
+        nil
+      (mapcar #'ai-code-mcp--display-path
+              (ai-code-mcp--project-files project-dir)))))

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