Static: supporting new "index" option.

This supports a new option "index" that configures a custom index
file name to be served when a directory is requested.  This
initial support only allows a single fixed string.  An example:

{
	"share": "/www/data/static/$uri",
	"index": "lookatthis.htm"
}

When <example.com/foo/bar/> is requested,
</www/data/static/foo/bar/lookatthis.html> is served.

Default is "index.html".

===

nxt_conf_validator.c:

Accept "index" as a member of "share", and make sure it's a string.

===

I tried this feature in my own computer, where I tried the
following:

- Setting "index" to "lookatthis.htm", and check that the correct
  file is being served (check both a different name and a
  different extension).
- Not setting "index", and check that <index.html> is being
  served.
- Settind "index" to an array of strings, and check that the
  configuration fails:

{
	"error": "Invalid configuration.",
	"detail": "The \"index\" value must be a string, but not an array."
}

docs/changes.xml

@@ -43,6 +43,12 @@ supporting empty strings in the "location" option of the "return" action.
 </para>
 </change>
 
+<change type="feature">
+<para>
+ability to specify a custom index file name when serving static files.
+</para>
+</change>
+
 <change type="feature">
 <para>
 variables support in the "location" option of the "return" action.

src/nxt_conf_validation.c

@@ -647,6 +647,9 @@ static nxt_conf_vldt_object_t  nxt_conf_vldt_share_action_members[] = {
         .name       = nxt_string("share"),
         .type       = NXT_CONF_VLDT_STRING | NXT_CONF_VLDT_ARRAY,
         .validator  = nxt_conf_vldt_share,
+    }, {
+        .name       = nxt_string("index"),
+        .type       = NXT_CONF_VLDT_STRING,
     }, {
         .name       = nxt_string("types"),
         .type       = NXT_CONF_VLDT_STRING | NXT_CONF_VLDT_ARRAY,

src/nxt_http.h

@@ -218,6 +218,7 @@ typedef struct {
     nxt_conf_value_t                *location;
     nxt_conf_value_t                *proxy;
     nxt_conf_value_t                *share;
+    nxt_conf_value_t                *index;
     nxt_str_t                       chroot;
     nxt_conf_value_t                *follow_symlinks;
     nxt_conf_value_t                *traverse_mounts;

src/nxt_http_route.c

@@ -610,6 +610,11 @@ static nxt_conf_map_t  nxt_http_route_action_conf[] = {
         NXT_CONF_MAP_PTR,
         offsetof(nxt_http_action_conf_t, share)
     },
+    {
+        nxt_string("index"),
+        NXT_CONF_MAP_PTR,
+        offsetof(nxt_http_action_conf_t, index)
+    },
     {
         nxt_string("chroot"),
         NXT_CONF_MAP_STR,

src/nxt_http_static.c

@@ -19,6 +19,7 @@ typedef struct {
 typedef struct {
     nxt_uint_t                  nshares;
     nxt_http_static_share_t     *shares;
+    nxt_str_t                   index;
 #if (NXT_HAVE_OPENAT2)
     nxt_var_t                   *chroot;
     nxt_uint_t                  resolve;
@@ -75,7 +76,7 @@ nxt_http_static_init(nxt_task_t *task, nxt_router_temp_conf_t *tmcf,
 {
     uint32_t                i;
     nxt_mp_t                *mp;
-    nxt_str_t               str;
+    nxt_str_t               str, *ret;
     nxt_var_t               *var;
     nxt_conf_value_t        *cv;
     nxt_http_static_conf_t  *conf;
@@ -110,6 +111,18 @@ nxt_http_static_init(nxt_task_t *task, nxt_router_temp_conf_t *tmcf,
         conf->shares[i].is_const = nxt_var_is_const(var);
     }
 
+    if (acf->index == NULL) {
+        nxt_str_set(&conf->index, "index.html");
+
+    } else {
+        nxt_conf_get_string(acf->index, &str);
+
+        ret = nxt_str_dup(mp, &conf->index, &str);
+        if (nxt_slow_path(ret == NULL)) {
+            return NXT_ERROR;
+        }
+    }
+
 #if (NXT_HAVE_OPENAT2)
     if (acf->chroot.length > 0) {
         nxt_str_t   chr, shr;
@@ -222,8 +235,10 @@ nxt_http_static_iterate(nxt_task_t *task, nxt_http_request_t *r,
 
 #if (NXT_DEBUG)
     nxt_str_t  shr;
+    nxt_str_t  idx;
 
     nxt_var_raw(share->var, &shr);
+    idx = conf->index;
 
 #if (NXT_HAVE_OPENAT2)
     nxt_str_t  chr;
@@ -235,9 +250,10 @@ nxt_http_static_iterate(nxt_task_t *task, nxt_http_request_t *r,
         nxt_str_set(&chr, "");
     }
 
-    nxt_debug(task, "http static: \"%V\" (chroot: \"%V\")", &shr, &chr);
+    nxt_debug(task, "http static: \"%V\", index: \"%V\" (chroot: \"%V\")",
+              &shr, &idx, &chr);
 #else
-    nxt_debug(task, "http static: \"%V\"", &shr);
+    nxt_debug(task, "http static: \"%V\", index: \"%V\"", &shr, &idx);
 #endif
 #endif /* NXT_DEBUG */
 
@@ -282,7 +298,7 @@ nxt_http_static_send_ready(nxt_task_t *task, void *obj, void *data)
     struct tm               tm;
     nxt_buf_t               *fb;
     nxt_int_t               ret;
-    nxt_str_t               *shr, exten, *mtype;
+    nxt_str_t               *shr, *index, exten, *mtype;
     nxt_uint_t              level;
     nxt_file_t              *f, file;
     nxt_file_info_t         fi;
@@ -295,8 +311,6 @@ nxt_http_static_send_ready(nxt_task_t *task, void *obj, void *data)
     nxt_http_static_ctx_t   *ctx;
     nxt_http_static_conf_t  *conf;
 
-    static const nxt_str_t  index = nxt_string("index.html");
-
     r = obj;
     ctx = data;
     action = ctx->action;
@@ -307,12 +321,12 @@ nxt_http_static_send_ready(nxt_task_t *task, void *obj, void *data)
     mtype = NULL;
 
     shr = &ctx->share;
+    index = &conf->index;
 
     if (shr->start[shr->length - 1] == '/') {
-        /* TODO: dynamic index setting. */
-        nxt_str_set(&exten, ".html");
+        nxt_http_static_extract_extension(index, &exten);
 
-        length = shr->length + index.length;
+        length = shr->length + index->length;
 
         fname = nxt_mp_nget(r->mem_pool, length + 1);
         if (nxt_slow_path(fname == NULL)) {
@@ -321,7 +335,7 @@ nxt_http_static_send_ready(nxt_task_t *task, void *obj, void *data)
 
         p = fname;
         p = nxt_cpymem(p, shr->start, shr->length);
-        p = nxt_cpymem(p, index.start, index.length);
+        p = nxt_cpymem(p, index->start, index->length);
         *p = '\0';
 
     } else {