From f20a79207c4b6f243e6de029f5f0fffd81dc0c1c Mon Sep 17 00:00:00 2001
From: Arun Isaac
Date: Mon, 15 Aug 2022 00:28:52 +0530
Subject: Track variables provided by certain features.

We track the value of variables provided by certain features. This is
so that we rebuild correctly when the user sets a configuration
variable.

* ennum.el: Require loadhist.
(ennum-track-features, ennum-feature-hash): New variables.
(ennum--feature-environment): New function.
(ennum-exp): Include ennum-feature-hash in hash computation.
(ennum-publish): Recompute ennum-feature-hash.
---
 ennum.el | 35 +++++++++++++++++++++++++++++++++++
 1 file changed, 35 insertions(+)

(limited to 'ennum.el')

diff --git a/ennum.el b/ennum.el
index 31e5e5f..7161eeb 100644
--- a/ennum.el
+++ b/ennum.el
@@ -5,6 +5,7 @@
 (require 'ox)
 (require 'seq)
 (require 'cl)
+(require 'loadhist)
 (require 'map)
 (require 'memoize)
 (require 'simple-httpd)
@@ -15,6 +16,14 @@
 (defvar ennum-blog nil
   "Property list specifying ennum publish settings")
 
+(defvar ennum-track-features
+  '(ennum ennum-html ennum-image ob-tangle org ox ox-html)
+  "List of features to track on expression evaluation.")
+
+(defvar ennum-feature-hash
+  nil
+  "List of hashes tracking current state of features.")
+
 ;; TODO: Should the store have an absolute path to deal with directory
 ;; changes? Yes, since we ask for an absolute working directory, we
 ;; should.
@@ -57,6 +66,28 @@ respectively by - and _, and the pad character = is optional."
     (insert file)
     (ennum--hash)))
 
+(defun ennum--feature-environment (feature)
+  "Return hash of the current state of FEATURE.
+
+The returned hash is the hash of the file providing FEATURE, and
+the current state of all its variables."
+  (pcase (feature-symbols feature)
+    (`(,file . ,entries)
+     (with-temp-buffer
+       ;; Print hash of file.
+       (print (ennum-file-hash file) (current-buffer))
+       ;; Print variables and their values.
+       (dolist (variable entries)
+         (print (if (and (atom variable)
+                         (boundp variable)
+                         ;; Exclude `ennum-feature-hash' since it
+                         ;; is meant to be changed on each run.
+                         (not (eq variable 'ennum-feature-hash)))
+                    (cons variable (symbol-value variable))
+                  variable)
+                (current-buffer)))
+       (ennum--hash)))))
+
 (defun ennum--set-file-modes-recursively (directory directory-mode file-mode executable-file-mode)
   (chmod directory directory-mode)
   (seq-do (lambda (file)
@@ -75,6 +106,7 @@ respectively by - and _, and the pad character = is optional."
           (with-temp-buffer
             (let ((print-length nil)
                   (print-level nil))
+              (print ennum-feature-hash (current-buffer))
               (print closure (current-buffer)))
             (ennum--hash))
           (ennum-setting :store))))
@@ -648,6 +680,9 @@ as keys. Keys are compared using `equal'."
 
 (defun ennum-publish ()
   (interactive)
+  ;; Recompute feature hash.
+  (setq ennum-feature-hash
+        (seq-map 'ennum--feature-environment ennum-track-features))
   (ennum-with-current-directory (ennum-setting :working-directory)
     (let* ((blog-title (ennum-setting :blog-title))
            (posts (ennum-posts (ennum-setting :posts-directory)))
-- 
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