feat(views): grouping source helpers and the effective-grouping resolver

Phase 1 of the interactive-grouping spec: the source/resolver plumbing, no command yet. pearl--grouping-choices maps the display labels (status/project/assignee/priority/none) to Linear's issueGrouping values. pearl--grouping-display-to-value coerces and pearl--check-grouping validates, both refusing anything outside that set. Cycle is left out on purpose: it isn't in the issue drawer, so an offline regroup can't read it.

pearl--source-with-grouping records the choice under :client-group for every source type, leaving a view's own server :group intact. Choosing none removes the key, so the source falls back to the server :group or to flat. pearl--effective-grouping returns :client-group when set, else :group. That's the single read every grouping consumer routes through in phase 4, so a refresh reproduces the layout on screen.

16 tests: coercion, validation, the source helper, resolver precedence, and the :client-group header round-trip.

2 files changed, 200 insertions, 0 deletions

diff --git a/pearl.el b/pearl.el
index 593cf47..662d7b9 100644
--- a/pearl.el
+++ b/pearl.el
@@ -4498,6 +4498,60 @@ view's server order is honored); every other source uses `:sort'/`:order'."
       (cons (plist-get source :client-sort) (plist-get source :client-order))
     (cons (plist-get source :sort) (plist-get source :order))))
 
+(defconst pearl--grouping-choices
+  '(("status"   . "workflowState")
+    ("project"  . "project")
+    ("assignee" . "assignee")
+    ("priority" . "priority")
+    ("none"     . nil))
+  "Interactive grouping dimensions: (DISPLAY . `issueGrouping' VALUE).
+DISPLAY is what `pearl-set-grouping' completes; VALUE is the Linear
+`issueGrouping' the render path speaks, or nil for \"none\" (ungroup).  `cycle'
+is intentionally absent: it isn't rendered into the issue drawer (see
+`pearl--format-issue-as-org-entry'), so an offline client-side regroup can't
+read it -- deferred until cycle drawer fields land.")
+
+(defun pearl--grouping-display-to-value (display)
+  "Coerce a DISPLAY grouping label to its `issueGrouping' value (or nil).
+Signals a `user-error' for a label outside `pearl--grouping-choices'."
+  (let ((cell (assoc display pearl--grouping-choices)))
+    (unless cell
+      (user-error "Unknown grouping %s; use one of %s"
+                  display (mapconcat #'car pearl--grouping-choices "/")))
+    (cdr cell)))
+
+(defun pearl--check-grouping (value)
+  "Validate a grouping VALUE; signal a `user-error' on an unknown one.
+Returns t when VALUE is nil (none) or one of the interactive grouping values
+\(`pearl--grouping-choices').  `cycle' and any other unsupported value are
+rejected -- the render path treats them as flat, but the interactive command
+refuses them before writing the header."
+  (let ((allowed (delq nil (mapcar #'cdr pearl--grouping-choices))))
+    (when (and value (not (member value allowed)))
+      (user-error "Unknown grouping %s; use %s or none"
+                  value (mapconcat #'car (butlast pearl--grouping-choices) "/"))))
+  t)
+
+(defun pearl--source-with-grouping (source value)
+  "Return SOURCE with grouping VALUE recorded under `:client-group'.
+VALUE is an `issueGrouping' string for all source types (uniform key); a view's
+own server `:group' is left intact so clearing the override restores it.  A nil
+VALUE (none) removes `:client-group' entirely, so `pearl--effective-grouping'
+falls back to the server `:group' (a view) or to flat (a filter)."
+  (if value
+      (plist-put (copy-sequence source) :client-group value)
+    (cl-loop for (k v) on source by #'cddr
+             unless (eq k :client-group) append (list k v))))
+
+(defun pearl--effective-grouping (source)
+  "Return the `issueGrouping' value SOURCE should render by, or nil for flat.
+An interactive `:client-group' overrides a view's server `:group'; with no
+override, a view uses its `:group' and a filter is flat.  Every grouping
+consumer (render, merge, append, refresh) reads through this so a refresh
+reproduces the layout on screen rather than the server grouping."
+  (or (plist-get source :client-group)
+      (plist-get source :group)))
+
 ;;; Sentinel infrastructure for filter / pick-one prompts
 ;;
 ;; These sentinel constants and helpers back the prompt UX shared by
diff --git a/tests/test-pearl-grouping.el b/tests/test-pearl-grouping.el
new file mode 100644
index 0000000..10902f1
--- /dev/null
+++ b/tests/test-pearl-grouping.el
@@ -0,0 +1,146 @@
+;;; test-pearl-grouping.el --- Tests for interactive grouping -*- lexical-binding: t; -*-
+
+;; Copyright (C) 2026 Craig Jennings
+
+;; Author: Craig Jennings <c@cjennings.net>
+
+;; This program is free software: you can redistribute it and/or modify
+;; it under the terms of the GNU General Public License as published by
+;; the Free Software Foundation, either version 3 of the License, or
+;; (at your option) any later version.
+
+;; This program is distributed in the hope that it will be useful,
+;; but WITHOUT ANY WARRANTY; without even the implied warranty of
+;; MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+;; GNU General Public License for more details.
+
+;; You should have received a copy of the GNU General Public License
+;; along with this program.  If not, see <http://www.gnu.org/licenses/>.
+
+;;; Commentary:
+
+;; Tests for grouping the active view interactively (docs/interactive-grouping-spec.org):
+;; the display<->value coercion and validation, the :client-group source
+;; helper and the effective-grouping resolver, the in-place regroup (subtree
+;; capture + heading-level shift + malformed-last), and the pearl-set-grouping
+;; command.  Phase 1 covers the source/resolver plumbing.
+
+;;; Code:
+
+(require 'test-bootstrap (expand-file-name "test-bootstrap.el"))
+(require 'cl-lib)
+
+(defmacro test-pearl-grouping--in-org (content &rest body)
+  "Run BODY in an org-mode temp buffer holding CONTENT."
+  (declare (indent 1))
+  `(let ((org-todo-keywords '((sequence "TODO" "IN-PROGRESS" "|" "DONE"))))
+     (with-temp-buffer
+       (insert ,content)
+       (org-mode)
+       (goto-char (point-min))
+       ,@body)))
+
+;;; display -> value coercion
+
+(ert-deftest test-pearl-grouping-display-to-value-maps-status ()
+  "The display label \"status\" coerces to Linear's `workflowState'."
+  (should (equal (pearl--grouping-display-to-value "status") "workflowState")))
+
+(ert-deftest test-pearl-grouping-display-to-value-identity-dimensions ()
+  "Project/assignee/priority coerce to their own Linear grouping value."
+  (should (equal (pearl--grouping-display-to-value "project") "project"))
+  (should (equal (pearl--grouping-display-to-value "assignee") "assignee"))
+  (should (equal (pearl--grouping-display-to-value "priority") "priority")))
+
+(ert-deftest test-pearl-grouping-display-to-value-none-is-nil ()
+  "The display label \"none\" coerces to nil (ungroup)."
+  (should (null (pearl--grouping-display-to-value "none"))))
+
+(ert-deftest test-pearl-grouping-display-to-value-unknown-errors ()
+  "An unknown display label signals a `user-error'."
+  (should-error (pearl--grouping-display-to-value "sideways") :type 'user-error))
+
+;;; validation
+
+(ert-deftest test-pearl-check-grouping-valid ()
+  "nil (none) and the four interactive grouping values pass."
+  (should (pearl--check-grouping nil))
+  (should (pearl--check-grouping "workflowState"))
+  (should (pearl--check-grouping "project"))
+  (should (pearl--check-grouping "priority")))
+
+(ert-deftest test-pearl-check-grouping-cycle-rejected ()
+  "`cycle' is deferred from interactive grouping (not in the drawer)."
+  (should-error (pearl--check-grouping "cycle") :type 'user-error))
+
+(ert-deftest test-pearl-check-grouping-unknown-rejected ()
+  "An unknown grouping value signals a `user-error'."
+  (should-error (pearl--check-grouping "bogus") :type 'user-error))
+
+;;; source helper
+
+(ert-deftest test-pearl-source-with-grouping-filter ()
+  "A filter records the interactive grouping under :client-group."
+  (let ((out (pearl--source-with-grouping '(:type filter :name "x") "workflowState")))
+    (should (equal (plist-get out :client-group) "workflowState"))))
+
+(ert-deftest test-pearl-source-with-grouping-view-keeps-server-group ()
+  "A view records :client-group, leaving its server :group untouched."
+  (let ((out (pearl--source-with-grouping
+              '(:type view :name "v" :id "vid" :group "project")
+              "assignee")))
+    (should (equal (plist-get out :client-group) "assignee"))
+    (should (equal (plist-get out :group) "project"))))
+
+(ert-deftest test-pearl-source-with-grouping-none-clears ()
+  "Grouping value nil (none) removes :client-group so the source falls back."
+  (let ((out (pearl--source-with-grouping
+              '(:type view :name "v" :id "vid" :group "project" :client-group "assignee")
+              nil)))
+    (should-not (plist-member out :client-group))
+    (should (equal (plist-get out :group) "project"))))
+
+;;; effective-grouping resolver
+
+(ert-deftest test-pearl-effective-grouping-view-client-overrides-server ()
+  "A view's :client-group overrides its server :group."
+  (should (equal (pearl--effective-grouping
+                  '(:type view :group "project" :client-group "assignee"))
+                 "assignee")))
+
+(ert-deftest test-pearl-effective-grouping-view-server-only ()
+  "A view with no :client-group renders by its server :group."
+  (should (equal (pearl--effective-grouping '(:type view :group "project"))
+                 "project")))
+
+(ert-deftest test-pearl-effective-grouping-view-neither-is-nil ()
+  "A view with neither key has no effective grouping (flat)."
+  (should (null (pearl--effective-grouping '(:type view :name "v")))))
+
+(ert-deftest test-pearl-effective-grouping-filter-client ()
+  "A filter renders by its :client-group."
+  (should (equal (pearl--effective-grouping '(:type filter :client-group "workflowState"))
+                 "workflowState")))
+
+(ert-deftest test-pearl-effective-grouping-none-cleared-falls-to-server ()
+  "After none clears :client-group, a view falls back to its server :group."
+  (let ((src (pearl--source-with-grouping
+              '(:type view :group "project" :client-group "assignee") nil)))
+    (should (equal (pearl--effective-grouping src) "project"))))
+
+;;; header persistence
+
+(ert-deftest test-pearl-grouping-client-group-roundtrips-in-header ()
+  "Writing a source with :client-group is read back by `pearl--read-active-source'."
+  (test-pearl-grouping--in-org
+      (concat
+       "#+LINEAR-SOURCE: (:type filter :name \"x\" :filter (:open t))\n\n"
+       "* x\n")
+    (pearl--write-linear-source-header
+     (pearl--source-with-grouping '(:type filter :name "x" :filter (:open t))
+                                  "workflowState"))
+    (should (equal (plist-get (pearl--read-active-source) :client-group)
+                   "workflowState"))))
+
+(provide 'test-pearl-grouping)
+;;; test-pearl-grouping.el ends here