Fix errors with developing Emacs built-in packages using Eldev (issue #102).

Author: doublep

eldev.el

@@ -2919,7 +2919,10 @@ Since 0.2."
       (clrhash considered)
       (throw 'restart-planning t))
     (unless (and considered-before (version-list-<= required-version considered-version))
-      (unless (package-built-in-p package-name required-version)
+      (when (or (not (package-built-in-p package-name required-version))
+                ;; See issue 102.  Do replace built-in packages with the project itself
+                ;; and local dependencies.  See `local' below.
+                (and (not self) (eldev--loading-mode package-name)))
         (when (eq package-name 'emacs)
           (when optional
             (eldev-verbose "Emacs version %s (this is %s) is %s; skipping the optional dependency"
@@ -3174,8 +3177,8 @@ for all archives instead."
 
 (defun eldev--loading-mode (dependency)
   "Get loading mode of package DEPENDENCY.
-DEPENDENCY can be either a name (symbol) or a package
-descriptor."
+DEPENDENCY can be either a name (symbol) or a package descriptor.
+Returns nil if it is neither a project nor a local dependency."
   (let ((dependency-name (if (symbolp dependency) dependency (package-desc-name dependency))))
     (if (eq dependency-name (package-desc-name (eldev-package-descriptor)))
         (or eldev-project-loading-mode 'as-is)

test/misc.el

@@ -36,6 +36,26 @@
       (should (= exit-code 0)))))
 
 
+(ert-deftest eldev-issue-102-1 ()
+  ;; Org is an Emacs built-in.  Make sure it still can be developed with Eldev.
+  (let ((eldev--test-project "project-fake-org"))
+    (eldev--test-delete-cache)
+    (eldev--test-run nil ("eval" `(bound-and-true-p org-is-fake))
+      (should (string= stdout "t\n"))
+      (should (= exit-code 0)))))
+
+(ert-deftest eldev-issue-102-2 ()
+  (let ((eldev--test-project "dependency-org"))
+    (eldev--test-run nil ("eval" `(progn (require 'org) (bound-and-true-p org-is-fake)))
+      (should (string= stdout "nil\n"))
+      (should (= exit-code 0)))
+    ;; Must load the local dependency if requested, even if Org is a built-in.
+    (eldev--test-run nil ("--setup" `(eldev-use-local-dependency "../project-fake-org")
+                          "eval" `(progn (require 'org) (bound-and-true-p org-is-fake)))
+      (should (string= stdout "t\n"))
+      (should (= exit-code 0)))))
+
+
 ;; Not a bug, just doesn't seem to fit anywhere else.  Test that
 ;; `eldev-known-tool-packages' can be customized.
 (ert-deftest eldev-known-tool-packages-1 ()

test/project-fake-org/org.el

@@ -0,0 +1,11 @@
+;;; org.el --- Fake of an Org snapshot
+
+;; Version: 99999999.9999
+
+(defvar org-version "99999999.9999")
+
+(defvar org-is-fake t)
+
+(provide 'org)
+
+;;; org.el ends here