Have a callback for static file handlers.

My usecase is to provide some caching headers by passing this callback: (lambda (path content-type) (declare (ignore path content-type)) (setf (hunchentoot:header-out "Cache-Control") "max-age=864000")) Sadly there've been &optional args; so, to avoid mixing &optional and &key args new function names are required.
edicl · Dec 20, 2019 · 2bd971c · 2bd971c
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diff --git a/docs/index.xml b/docs/index.xml
@@ -1194,7 +1194,7 @@
       </clix:function>
 
       <clix:function name="create-folder-dispatcher-and-handler">
-        <clix:lambda-list>uri-prefix base-path <clix:lkw>optional</clix:lkw> content-type</clix:lambda-list>
+        <clix:lambda-list>uri-prefix base-path <clix:lkw>optional</clix:lkw> content-type callback</clix:lambda-list>
         <clix:returns>dispatch-fn</clix:returns>
         <clix:description>
           Creates and returns a dispatch function which will dispatch to
@@ -1213,13 +1213,17 @@
             the content type of each file will be
             determined <a href="#handle-static-file">as usual</a>.
           </p>
+          <p>
+            The <clix:arg>callback</clix:arg> is passed on to
+            <clix:ref>HANDLE-STATIC-FILE</clix:ref>.
+          </p>
         </clix:description>
       </clix:function>
 
       <clix:function name='create-static-file-dispatcher-and-handler'>
         <clix:lambda-list>uri path
         <clix:lkw>optional
-        </clix:lkw> content-type
+        </clix:lkw> content-type callback
         </clix:lambda-list>
         <clix:returns>result
         </clix:returns>
@@ -1230,6 +1234,10 @@
           CONTENT-TYPE if the SCRIPT-NAME of the request matches the
           string URI.  If CONTENT-TYPE is NIL, tries to determine the
           content type via the file&#039;s suffix.
+          <p>
+            The <clix:arg>callback</clix:arg> is passed on to
+            <clix:ref>HANDLE-STATIC-FILE</clix:ref>.
+          </p>
         </clix:description>
       </clix:function>
 
@@ -3263,7 +3271,7 @@
       </clix:function>
 
       <clix:function name="handle-static-file">
-        <clix:lambda-list>path <clix:lkw>optional</clix:lkw> content-type</clix:lambda-list>
+        <clix:lambda-list>path <clix:lkw>optional</clix:lkw> content-type callback</clix:lambda-list>
         <clix:returns>nil</clix:returns>
         <clix:description>
           Sends the file denoted by the pathname designator
@@ -3272,11 +3280,16 @@
           necessary handlers.  In particular the function employs
           <clix:ref>HANDLE-IF-MODIFIED-SINCE</clix:ref>.
           <p>
-            If <clix:arg>content-type</clix:arg> is <code>NIL</code> the
+            If <clix:arg>content-type</clix:arg> is <code>NIL</code>, the
             function tries to determine the correct content type from
             the file's suffix or falls back
             to <code>"application/octet-stream"</code> as a last resort.
           </p>
+          <p>
+            The <clix:arg>callback</clix:arg> is run just before opening
+            the file; it can eg. check authorization or send caching headers.
+            It gets the filename and the (guessed) content-type as arguments.
+          </p>
           <p>
             Note that this function
             calls <clix:ref>SEND-HEADERS</clix:ref> internally, so after

diff --git a/misc.lisp b/misc.lisp
@@ -148,11 +148,14 @@ had returned RESULT.  See the source code of REDIRECT for an example."
             (header-out :content-range) (format nil "bytes ~D-~D/~D" start end (file-length file))))
     bytes-to-send))
 
-(defun handle-static-file (pathname &optional content-type)
+(defun handle-static-file (pathname &optional content-type callback)
   "A function which acts like a Hunchentoot handler for the file
 denoted by PATHNAME.  Sends a content type header corresponding to
 CONTENT-TYPE or \(if that is NIL) tries to determine the content type
-via the file's suffix."
+via the suffix of the file.
+CALLBACK is run just before sending the file, and can be used
+to set headers or check authorization;
+arguments are the filename and the (guessed) content-type."
   (when (or (wild-pathname-p pathname)
             (not (fad:file-exists-p pathname))
             (fad:directory-exists-p pathname))
@@ -170,6 +173,8 @@ via the file's suffix."
           (header-out :last-modified) (rfc-1123-date time)
           (header-out :accept-ranges) "bytes")
     (handle-if-modified-since time)
+    (unless (null callback)
+      (funcall callback pathname content-type))
     (with-open-file (file pathname
                           :direction :input
                           :element-type 'octet)
@@ -187,26 +192,28 @@ via the file's suffix."
              (decf bytes-to-send chunk-size)))
         (finish-output out)))))
 
-(defun create-static-file-dispatcher-and-handler (uri path &optional content-type)
+(defun create-static-file-dispatcher-and-handler (uri path &optional content-type callback)
   "Creates and returns a request dispatch function which will dispatch
 to a handler function which emits the file denoted by the pathname
 designator PATH with content type CONTENT-TYPE if the SCRIPT-NAME of
 the request matches the string URI.  If CONTENT-TYPE is NIL, tries to
-determine the content type via the file's suffix."
+determine the content type via the file's suffix.
+See HANDLE-STATIC-FILE for CALLBACK."
   ;; the dispatcher
   (lambda (request)
     (when (string= (script-name request) uri)
       ;; the handler
       (lambda ()
-        (handle-static-file path content-type)))))
+        (handle-static-file path content-type callback)))))
 
-(defun create-folder-dispatcher-and-handler (uri-prefix base-path &optional content-type)
+(defun create-folder-dispatcher-and-handler (uri-prefix base-path &key content-type callback)
   "Creates and returns a dispatch function which will dispatch to a
 handler function which emits the file relative to BASE-PATH that is
 denoted by the URI of the request relative to URI-PREFIX.  URI-PREFIX
 must be a string ending with a slash, BASE-PATH must be a pathname
 designator for an existing directory.  If CONTENT-TYPE is not NIL,
-it'll be the content type used for all files in the folder."
+it'll be the content type used for all files in the folder.
+See HANDLE-STATIC-FILE for CALLBACK."
   (unless (and (stringp uri-prefix)
                (plusp (length uri-prefix))
                (char= (char uri-prefix (1- (length uri-prefix))) #\/))
@@ -218,7 +225,9 @@ it'll be the content type used for all files in the folder."
              (when (null request-path)
                (setf (return-code*) +http-forbidden+)
                (abort-request-handler))
-             (handle-static-file (merge-pathnames request-path base-path) content-type))))
+             (handle-static-file (merge-pathnames request-path base-path)
+                                  content-type
+                                  callback))))
     (create-prefix-dispatcher uri-prefix #'handler)))
 
 (defun no-cache ()

diff --git a/www/hunchentoot-doc.html b/www/hunchentoot-doc.html
@@ -1165,7 +1165,7 @@ <h4 xmlns=""><a name="easy-handlers">Using the easy-handler framework</a></h4>
 
       <p xmlns=""><a class="none" name="create-folder-dispatcher-and-handler"></a>
           [Function]
-          <br><b>create-folder-dispatcher-and-handler</b> <i><clix:lambda-list xmlns:clix="http://bknr.net/clixdoc">uri-prefix base-path <tt>&amp;optional</tt> content-type</clix:lambda-list></i>
+          <br><b>create-folder-dispatcher-and-handler</b> <i><clix:lambda-list xmlns:clix="http://bknr.net/clixdoc">uri-prefix base-path <tt>&amp;optional</tt> content-type callback</clix:lambda-list></i>
             =&gt;
             <i><clix:returns xmlns:clix="http://bknr.net/clixdoc">dispatch-fn</clix:returns></i><blockquote><clix:description xmlns:clix="http://bknr.net/clixdoc">
           Creates and returns a dispatch function which will dispatch to
@@ -1184,13 +1184,17 @@ <h4 xmlns=""><a name="easy-handlers">Using the easy-handler framework</a></h4>
             the content type of each file will be
             determined <a href="#handle-static-file">as usual</a>.
           </p>
+          <p xmlns="http://www.w3.org/1999/xhtml">
+            The <code xmlns=""><i>callback</i></code> is passed on to
+            <code xmlns=""><a href="#handle-static-file">HANDLE-STATIC-FILE</a></code>.
+          </p>
         </clix:description></blockquote></p>
 
       <p xmlns=""><a class="none" name="create-static-file-dispatcher-and-handler"></a>
           [Function]
           <br><b>create-static-file-dispatcher-and-handler</b> <i><clix:lambda-list xmlns:clix="http://bknr.net/clixdoc">uri path
         <tt>&amp;optional
-        </tt> content-type
+        </tt> content-type callback
         </clix:lambda-list></i>
             =&gt;
             <i><clix:returns xmlns:clix="http://bknr.net/clixdoc">result
@@ -1201,6 +1205,10 @@ <h4 xmlns=""><a name="easy-handlers">Using the easy-handler framework</a></h4>
           CONTENT-TYPE if the SCRIPT-NAME of the request matches the
           string URI.  If CONTENT-TYPE is NIL, tries to determine the
           content type via the file's suffix.
+          <p xmlns="http://www.w3.org/1999/xhtml">
+            The <code xmlns=""><i>callback</i></code> is passed on to
+            <code xmlns=""><a href="#handle-static-file">HANDLE-STATIC-FILE</a></code>.
+          </p>
         </clix:description></blockquote></p>
 
       <p xmlns=""><a class="none" name="define-easy-handler"></a>
@@ -3143,7 +3151,7 @@ <h4 xmlns=""><a name="misc">Miscellaneous</a></h4>
 
       <p xmlns=""><a class="none" name="handle-static-file"></a>
           [Function]
-          <br><b>handle-static-file</b> <i><clix:lambda-list xmlns:clix="http://bknr.net/clixdoc">path <tt>&amp;optional</tt> content-type</clix:lambda-list></i>
+          <br><b>handle-static-file</b> <i><clix:lambda-list xmlns:clix="http://bknr.net/clixdoc">path <tt>&amp;optional</tt> content-type callback</clix:lambda-list></i>
             =&gt;
             <i><clix:returns xmlns:clix="http://bknr.net/clixdoc">nil</clix:returns></i><blockquote><clix:description xmlns:clix="http://bknr.net/clixdoc">
           Sends the file denoted by the pathname designator
@@ -3152,11 +3160,16 @@ <h4 xmlns=""><a name="misc">Miscellaneous</a></h4>
           necessary handlers.  In particular the function employs
           <code><a href="#handle-if-modified-since">HANDLE-IF-MODIFIED-SINCE</a></code>.
           <p xmlns="http://www.w3.org/1999/xhtml">
-            If <code xmlns=""><i>content-type</i></code> is <code>NIL</code> the
+            If <code xmlns=""><i>content-type</i></code> is <code>NIL</code>, the
             function tries to determine the correct content type from
             the file's suffix or falls back
             to <code>"application/octet-stream"</code> as a last resort.
           </p>
+          <p xmlns="http://www.w3.org/1999/xhtml">
+            The <code xmlns=""><i>callback</i></code> is run just before opening
+            the file; it can eg. check authorization or send caching headers.
+            It gets the filename and the (guessed) content-type as arguments.
+          </p>
           <p xmlns="http://www.w3.org/1999/xhtml">
             Note that this function
             calls <code xmlns=""><a href="#send-headers">SEND-HEADERS</a></code> internally, so after