Soft-deprecate prefix-less dirconfig entriesdirconfig-refactor

The implicit "any unprefixed line is an ignore pattern" rule is the
last source of subtle parser surprises — it's the reason why a
single leading space silently changes a +-keep into a literal ignore
pattern, and it makes typo'd comments slip through as ignores.

Mark these lines as :legacy-ignore in the classifier, record them
in a new prefixless-ignore slot on the dirconfig struct, and emit a
one-time warning per project listing the offending entries. The
behavior is unchanged — the lines still go into the ignore list —
but users now get a nudge to write them as -entry. The warning can
be silenced via projectile-warn-on-prefixless-dirconfig-lines.

4 files changed, 140 insertions, 34 deletions

diff --git a/CHANGELOG.md b/CHANGELOG.md
index e4e33a2..24b0cd1 100644
--- a/CHANGELOG.md
+++ b/CHANGELOG.md
@@ -4,7 +4,8 @@
 
 ### Changes
 
-* `projectile-parse-dirconfig-file' now returns a `projectile-dirconfig' struct (with `keep', `ignore', and `ensure' slots) instead of a positional 3-tuple. External callers should use the accessors (`projectile-dirconfig-keep' etc.) rather than `car'/`cadr'/`caddr'.
+* `projectile-parse-dirconfig-file' now returns a `projectile-dirconfig' struct (with `keep', `ignore', `ensure', and `prefixless-ignore' slots) instead of a positional 3-tuple. External callers should use the accessors (`projectile-dirconfig-keep' etc.) rather than `car'/`cadr'/`caddr'.
+* Soft-deprecate prefix-less ignore entries in `.projectile'. Lines without a `+'/`-'/`!' prefix are still treated as ignore patterns for backward compatibility, but a one-time warning is now shown for each project that uses them. Set `projectile-warn-on-prefixless-dirconfig-lines' to nil to silence.
 
 ### New features
 
diff --git a/doc/modules/ROOT/pages/projects.adoc b/doc/modules/ROOT/pages/projects.adoc
index f1f4a5f..24e6e31 100644
--- a/doc/modules/ROOT/pages/projects.adoc
+++ b/doc/modules/ROOT/pages/projects.adoc
@@ -813,8 +813,13 @@ If you'd like to instruct Projectile to ignore certain files in a
 project, when indexing it you can do so in the `.projectile` file by
 adding each path to ignore, where the paths all are relative to the
 root directory and start with a slash. Everything ignored should be
-preceded with a `-` sign. Alternatively, not having any prefix at all
-also means to ignore the directory or file pattern that follows.
+preceded with a `-` sign.
+
+NOTE: Lines without any prefix at all are still accepted and treated
+as ignore patterns for backward compatibility, but the implicit form
+is being phased out and Projectile now warns about it once per
+project.  Prefer the explicit `-` prefix in new dirconfigs.
+
 Here's an example for a typical Rails application:
 
 ----
diff --git a/projectile.el b/projectile.el
index 7217397..f600597 100644
--- a/projectile.el
+++ b/projectile.el
@@ -415,6 +415,17 @@ silent bypass is a frequent source of confusion."
   :type 'boolean
   :package-version '(projectile . "2.10.0"))
 
+(defcustom projectile-warn-on-prefixless-dirconfig-lines t
+  "Whether to warn about deprecated prefix-less ignore entries.
+Lines in `.projectile' that start with no `+'/`-'/`!' prefix are
+still accepted as ignore patterns for backward compatibility, but
+the implicit form is being phased out.  When this option is
+non-nil, a one-time warning is shown per project that uses any
+such line, listing the offending entries."
+  :group 'projectile
+  :type 'boolean
+  :package-version '(projectile . "2.10.0"))
+
 (defcustom projectile-globally-ignored-files
   (list projectile-tags-file-name projectile-cache-file)
   "A list of files globally ignored by projectile.
@@ -667,6 +678,9 @@ Each value is a cons of (MTIME . PARSED-RESULT).")
 (defvar projectile--alien-dirconfig-warned-projects (make-hash-table :test 'equal)
   "Set of project roots already warned about alien indexing skipping the dirconfig.")
 
+(defvar projectile--prefixless-dirconfig-warned-projects (make-hash-table :test 'equal)
+  "Set of project roots already warned about prefix-less dirconfig entries.")
+
 (defvar projectile-known-projects nil
   "List of locations where we have previously seen projects.
 The list of projects is ordered by the time they have been accessed.
@@ -2193,9 +2207,11 @@ Unignored files/directories are not included."
 KEEP is the list of subdirectories to restrict the project to (as
 returned with a trailing slash).  IGNORE and ENSURE are the lists
 of files or directories to ignore and to forcibly include,
-respectively.  All slots default to nil, which represents \"no
-file present or no entries of this kind\"."
-  (keep nil) (ignore nil) (ensure nil))
+respectively.  PREFIXLESS-IGNORE is the subset of IGNORE entries
+that arrived without a leading `+'/`-'/`!'/comment marker; they
+are accepted for backward compatibility but recorded separately so
+callers can flag the deprecated syntax.  All slots default to nil."
+  (keep nil) (ignore nil) (ensure nil) (prefixless-ignore nil))
 
 (defun projectile--warn-glob-in-keep-entry (entry dirconfig)
   "Warn that ENTRY in DIRCONFIG looks like a glob pattern after a `+'.
@@ -2212,9 +2228,12 @@ or move the pattern to a `-'/`!' rule."
 (defun projectile--dirconfig-classify-line (line)
   "Classify LINE from a dirconfig file.
 Return a cons (BUCKET . VALUE) where BUCKET is one of `:keep',
-`:ignore', `:ensure', or `:comment'.  Return nil for a blank line.
-Leading whitespace is skipped before dispatch so an accidental space
-or tab before the prefix does not change classification."
+`:ignore', `:ensure', `:legacy-ignore', or `:comment'.  Return nil
+for a blank line.  Leading whitespace is skipped before dispatch
+so an accidental space or tab before the prefix does not change
+classification.  `:legacy-ignore' is reserved for prefix-less
+lines, which are still treated as ignore patterns for backward
+compatibility but are tracked separately so callers can warn."
   (let* ((trimmed (string-trim-left line))
          (first-char (and (> (length trimmed) 0) (aref trimmed 0))))
     (cond
@@ -2222,23 +2241,27 @@ or tab before the prefix does not change classification."
      ((and projectile-dirconfig-comment-prefix
            (eql first-char projectile-dirconfig-comment-prefix))
       (cons :comment nil))
-     ((eql first-char ?+) (cons :keep   (string-trim (substring trimmed 1))))
-     ((eql first-char ?-) (cons :ignore (string-trim (substring trimmed 1))))
-     ((eql first-char ?!) (cons :ensure (string-trim (substring trimmed 1))))
-     (t                   (cons :ignore (string-trim trimmed))))))
+     ((eql first-char ?+) (cons :keep          (string-trim (substring trimmed 1))))
+     ((eql first-char ?-) (cons :ignore        (string-trim (substring trimmed 1))))
+     ((eql first-char ?!) (cons :ensure        (string-trim (substring trimmed 1))))
+     (t                   (cons :legacy-ignore (string-trim trimmed))))))
 
 (defun projectile--parse-dirconfig-string (text)
   "Parse TEXT (a dirconfig file's contents) into a `projectile-dirconfig'."
-  (let (keep ignore ensure)
+  (let (keep ignore ensure prefixless)
     (dolist (line (split-string text "\n"))
       (pcase (projectile--dirconfig-classify-line line)
-        (`(:keep   . ,v) (unless (string-empty-p v) (push v keep)))
-        (`(:ignore . ,v) (unless (string-empty-p v) (push v ignore)))
-        (`(:ensure . ,v) (unless (string-empty-p v) (push v ensure)))))
+        (`(:keep . ,v)          (unless (string-empty-p v) (push v keep)))
+        (`(:ignore . ,v)        (unless (string-empty-p v) (push v ignore)))
+        (`(:ensure . ,v)        (unless (string-empty-p v) (push v ensure)))
+        (`(:legacy-ignore . ,v) (unless (string-empty-p v)
+                                  (push v ignore)
+                                  (push v prefixless)))))
     (make-projectile-dirconfig
-     :keep   (mapcar #'file-name-as-directory (nreverse keep))
-     :ignore (nreverse ignore)
-     :ensure (nreverse ensure))))
+     :keep              (mapcar #'file-name-as-directory (nreverse keep))
+     :ignore            (nreverse ignore)
+     :ensure            (nreverse ensure)
+     :prefixless-ignore (nreverse prefixless))))
 
 (defun projectile--parse-dirconfig-file-uncached ()
   "Parse the dirconfig file without caching.
@@ -2254,6 +2277,28 @@ Return a `projectile-dirconfig' or nil if the file doesn't exist."
             (projectile--warn-glob-in-keep-entry entry dirconfig)))
         cfg))))
 
+(defun projectile--maybe-warn-prefixless-entries (project-root cfg)
+  "Warn once per session about prefix-less ignore entries in CFG for PROJECT-ROOT.
+CFG is a `projectile-dirconfig' struct."
+  (when (and projectile-warn-on-prefixless-dirconfig-lines
+             cfg
+             (projectile-dirconfig-prefixless-ignore cfg)
+             (not (gethash project-root
+                           projectile--prefixless-dirconfig-warned-projects)))
+    (puthash project-root t projectile--prefixless-dirconfig-warned-projects)
+    (display-warning
+     'projectile
+     (format "%s contains entries without a `+'/`-'/`!' prefix: %s.  \
+The implicit form is treated as an ignore rule for backward \
+compatibility but is being phased out — please prefix the lines \
+explicitly.  Set `projectile-warn-on-prefixless-dirconfig-lines' \
+to nil to silence this warning."
+             (expand-file-name projectile-dirconfig-file project-root)
+             (mapconcat (lambda (s) (format "`%s'" s))
+                        (projectile-dirconfig-prefixless-ignore cfg)
+                        ", "))
+     :warning)))
+
 (defun projectile-parse-dirconfig-file ()
   "Parse project ignore file and return its rules.
 
@@ -2280,13 +2325,17 @@ dirconfig file's modification time changes."
          (project-root (projectile-project-root))
          (cached (gethash project-root projectile--dirconfig-cache))
          (attrs (file-attributes dirconfig))
-         (mtime (when attrs (file-attribute-modification-time attrs))))
-    (if (and cached mtime (equal (car cached) mtime))
-        (cdr cached)
-      (let ((result (projectile--parse-dirconfig-file-uncached)))
-        (when mtime
-          (puthash project-root (cons mtime result) projectile--dirconfig-cache))
-        result))))
+         (mtime (when attrs (file-attribute-modification-time attrs)))
+         (result (if (and cached mtime (equal (car cached) mtime))
+                     (cdr cached)
+                   (let ((parsed (projectile--parse-dirconfig-file-uncached)))
+                     (when mtime
+                       (puthash project-root
+                                (cons mtime parsed)
+                                projectile--dirconfig-cache))
+                     parsed))))
+    (projectile--maybe-warn-prefixless-entries project-root result)
+    result))
 
 (defun projectile-expand-root (name &optional dir)
   "Expand NAME to project root.
diff --git a/test/projectile-test.el b/test/projectile-test.el
index fc6116d..9516ff1 100644
--- a/test/projectile-test.el
+++ b/test/projectile-test.el
@@ -539,9 +539,9 @@ Just delegates OPERATION and ARGS for all operations except for`shell-command`'.
             :to-equal '(:ignore . "/build"))
     (expect (projectile--dirconfig-classify-line "!/build/keepme")
             :to-equal '(:ensure . "/build/keepme")))
-  (it "treats prefix-less lines as ignore for backward compatibility"
+  (it "tags prefix-less lines as legacy-ignore for backward compatibility"
     (expect (projectile--dirconfig-classify-line "stale-pattern")
-            :to-equal '(:ignore . "stale-pattern")))
+            :to-equal '(:legacy-ignore . "stale-pattern")))
   (it "skips leading whitespace before dispatch"
     (expect (projectile--dirconfig-classify-line "  -indented")
             :to-equal '(:ignore . "indented"))
@@ -556,7 +556,7 @@ Just delegates OPERATION and ARGS for all operations except for`shell-command`'.
     ;; Without a comment prefix, # is just a regular character.
     (let ((projectile-dirconfig-comment-prefix nil))
       (expect (projectile--dirconfig-classify-line "#may-be-a-comment")
-              :to-equal '(:ignore . "#may-be-a-comment")))))
+              :to-equal '(:legacy-ignore . "#may-be-a-comment")))))
 
 (describe "projectile-parse-dirconfig-file"
   (it "parses dirconfig and returns directories to ignore and keep"
@@ -572,7 +572,11 @@ Just delegates OPERATION and ARGS for all operations except for`shell-command`'.
                                  "#may-be-a-comment"
                                  "no-prefix"
                                  "left-wspace"
-                                 "right-wspace")))
+                                 "right-wspace")
+                       :prefixless-ignore '("#may-be-a-comment"
+                                            "no-prefix"
+                                            "left-wspace"
+                                            "right-wspace")))
     ;; same test - but with comment lines enabled using prefix '#'
     (let ((projectile-dirconfig-comment-prefix ?#))
       (expect (projectile-parse-dirconfig-file)
@@ -581,7 +585,10 @@ Just delegates OPERATION and ARGS for all operations except for`shell-command`'.
                          :ignore '("exclude"
                                    "no-prefix"
                                    "left-wspace"
-                                   "right-wspace")))))
+                                   "right-wspace")
+                         :prefixless-ignore '("no-prefix"
+                                              "left-wspace"
+                                              "right-wspace")))))
   (it "skips leading whitespace before dispatching on the prefix"
     (spy-on 'file-exists-p :and-return-value t)
     (spy-on 'insert-file-contents :and-call-fake
@@ -595,7 +602,8 @@ Just delegates OPERATION and ARGS for all operations except for`shell-command`'.
             :to-equal (make-projectile-dirconfig
                        :keep '("indented-include/")
                        :ignore '("indented-exclude" "no-prefix-indented")
-                       :ensure '("indented-ensure"))))
+                       :ensure '("indented-ensure")
+                       :prefixless-ignore '("no-prefix-indented"))))
   (it "treats indented comment-prefix lines as comments"
     (spy-on 'file-exists-p :and-return-value t)
     (spy-on 'insert-file-contents :and-call-fake
@@ -649,7 +657,8 @@ Just delegates OPERATION and ARGS for all operations except for`shell-command`'.
                 :to-equal (make-projectile-dirconfig
                            :keep '("/src/")
                            :ignore '("/build" "stale-pattern")
-                           :ensure '("/build/keepme")))))))
+                           :ensure '("/build/keepme")
+                           :prefixless-ignore '("stale-pattern")))))))
   (it "round-trips non-ASCII paths through the parser"
     (projectile-test-with-sandbox
      (projectile-test-with-files
@@ -734,6 +743,48 @@ Just delegates OPERATION and ARGS for all operations except for`shell-command`'.
         (projectile-invalidate-cache nil)
         (expect (gethash root projectile--dirconfig-cache) :to-be nil))))))
 
+(describe "prefix-less dirconfig warning"
+  (before-each
+    (clrhash projectile--dirconfig-cache)
+    (clrhash projectile--prefixless-dirconfig-warned-projects))
+  (it "warns once when a dirconfig contains prefix-less ignore lines"
+    (projectile-test-with-sandbox
+     (projectile-test-with-files
+      ("project/.projectile")
+      (let ((root (file-truename (expand-file-name "project/"))))
+        (with-temp-file (expand-file-name ".projectile" root)
+          (insert "-foo\nstale-pattern\n"))
+        (spy-on 'projectile-project-root :and-return-value root)
+        (spy-on 'display-warning)
+        (let ((projectile-warn-on-prefixless-dirconfig-lines t))
+          (projectile-parse-dirconfig-file)
+          (projectile-parse-dirconfig-file))
+        (expect 'display-warning :to-have-been-called-times 1)))))
+  (it "does not warn for a fully-prefixed dirconfig"
+    (projectile-test-with-sandbox
+     (projectile-test-with-files
+      ("project/.projectile")
+      (let ((root (file-truename (expand-file-name "project/"))))
+        (with-temp-file (expand-file-name ".projectile" root)
+          (insert "-foo\n+/src\n!/build/keep\n"))
+        (spy-on 'projectile-project-root :and-return-value root)
+        (spy-on 'display-warning)
+        (let ((projectile-warn-on-prefixless-dirconfig-lines t))
+          (projectile-parse-dirconfig-file))
+        (expect 'display-warning :not :to-have-been-called)))))
+  (it "does not warn when the option is disabled"
+    (projectile-test-with-sandbox
+     (projectile-test-with-files
+      ("project/.projectile")
+      (let ((root (file-truename (expand-file-name "project/"))))
+        (with-temp-file (expand-file-name ".projectile" root)
+          (insert "stale-pattern\n"))
+        (spy-on 'projectile-project-root :and-return-value root)
+        (spy-on 'display-warning)
+        (let ((projectile-warn-on-prefixless-dirconfig-lines nil))
+          (projectile-parse-dirconfig-file))
+        (expect 'display-warning :not :to-have-been-called))))))
+
 (describe "alien-mode dirconfig warning"
   (before-each
     (clrhash projectile--alien-dirconfig-warned-projects))