Add headers if not set

README.markdown

@@ -74,6 +74,9 @@ Synopsis
 
  # replace input header X-Foo *only* if it already exists
  more_set_input_headers -r 'X-Foo: howdy';
+
+ # add input header X-Foo *only* if it does not exist
+ more_set_input_headers -a 'X-Foo: howdy';
 ```
 
 Description
@@ -134,7 +137,7 @@ Directives
 
 more_set_headers
 ----------------
-**syntax:** *more_set_headers [-t <content-type list>]... [-s <status-code list>]... <new-header>...*
+**syntax:** *more_set_headers [-a] [-t <content-type list>]... [-s <status-code list>]... <new-header>...*
 
 **default:** *no*
 
@@ -153,6 +156,8 @@ If either `-s` or `-t` is not specified or has an empty list value, then no matc
 
 Existing response headers with the same name are always overridden. If you want to add headers incrementally, use the standard [add_header](http://nginx.org/en/docs/http/ngx_http_headers_module.html#add_header) directive instead.
 
+If the `-a` option is specified, then the headers will be added *only if* they do not exist.
+
 A single directive can set/add multiple output headers. For example
 
 ```nginx
@@ -261,7 +266,7 @@ The `*` wildcard support was first introduced in [v0.09](#v009).
 
 more_set_input_headers
 ----------------------
-**syntax:** *more_set_input_headers [-r] [-t <content-type list>]... <new-header>...*
+**syntax:** *more_set_input_headers [-r] [-a] [-t <content-type list>]... <new-header>...*
 
 **default:** *no*
 
@@ -280,6 +285,8 @@ and works in subrequests as well.
 
 If the `-r` option is specified, then the headers will be replaced to the new values *only if* they already exist.
 
+If the `-a` options is specified, then the headers will be added *only if* they do not exist.
+
 [Back to TOC](#table-of-contents)
 
 more_clear_input_headers

src/ngx_http_headers_more_filter_module.h

@@ -61,6 +61,7 @@ struct ngx_http_headers_more_header_val_s {
     ngx_http_headers_more_set_header_pt     handler;
     ngx_uint_t                              offset;
     ngx_flag_t                              replace;
+    ngx_flag_t                              add_only;
     ngx_flag_t                              wildcard;
 };
 

src/ngx_http_headers_more_headers_in.c

@@ -247,33 +247,34 @@ ngx_http_set_header_helper(ngx_http_request_t *r,
             && ngx_strncasecmp(h[i].key.data, hv->key.data,
                                h[i].key.len) == 0)
         {
-            if (value->len == 0 || (matched && matched != &h[i])) {
-                h[i].hash = 0;
+            if (!(hv->add_only && !hv->replace)) {
+                if (value->len == 0 || (matched && matched != &h[i])) {
+                    h[i].hash = 0;
 
-                rc = ngx_http_headers_more_rm_header_helper(
+                    rc = ngx_http_headers_more_rm_header_helper(
                                             &r->headers_in.headers, part, i);
 
-                ngx_http_headers_more_assert(
-                    !(r->headers_in.headers.part.next == NULL
-                      && r->headers_in.headers.last
-                         != &r->headers_in.headers.part));
+                    ngx_http_headers_more_assert(
+                        !(r->headers_in.headers.part.next == NULL
+                          && r->headers_in.headers.last
+                             != &r->headers_in.headers.part));
 
-                if (rc == NGX_OK) {
-                    if (output_header) {
-                        *output_header = NULL;
+                    if (rc == NGX_OK) {
+                        if (output_header) {
+                            *output_header = NULL;
+                        }
+
+                        goto retry;
                     }
 
-                    goto retry;
+                    return NGX_ERROR;
                 }
+                h[i].value = *value;
 
-                return NGX_ERROR;
-            }
-
-            h[i].value = *value;
-
-            if (output_header) {
-                *output_header = &h[i];
-                dd("setting existing builtin input header");
+                if (output_header) {
+                    *output_header = &h[i];
+                    dd("setting existing builtin input header");
+                }
             }
 
             if (matched == NULL) {
@@ -286,7 +287,7 @@ ngx_http_set_header_helper(ngx_http_request_t *r,
         return NGX_OK;
     }
 
-    if (value->len == 0 || hv->replace) {
+    if (value->len == 0 || (hv->replace && !hv->add_only)) {
         return NGX_OK;
     }
 
@@ -358,6 +359,11 @@ ngx_http_set_builtin_header(ngx_http_request_t *r,
         return ngx_http_set_header_helper(r, hv, value, old);
     }
 
+    if (hv->add_only) {
+        dd("skip because %s does set", hv->key.data);
+        return NGX_OK;
+    }
+
     h = *old;
 
     if (value->len == 0) {
@@ -496,17 +502,17 @@ static char *
 ngx_http_headers_more_parse_directive(ngx_conf_t *cf, ngx_command_t *ngx_cmd,
     void *conf, ngx_http_headers_more_opcode_t opcode)
 {
+    ngx_flag_t                          replace = 0;
+    ngx_flag_t                          add_only = 0;
     ngx_http_headers_more_loc_conf_t   *hlcf = conf;
 
-    ngx_uint_t                          i;
-    ngx_http_headers_more_cmd_t        *cmd;
     ngx_str_t                          *arg;
-    ngx_flag_t                          ignore_next_arg;
     ngx_str_t                          *cmd_name;
     ngx_int_t                           rc;
-    ngx_flag_t                          replace = 0;
+    ngx_uint_t                          i;
+    ngx_flag_t                          ignore_next_arg;
+    ngx_http_headers_more_cmd_t        *cmd;
     ngx_http_headers_more_header_val_t *h;
-
     ngx_http_headers_more_main_conf_t  *hmcf;
 
     if (hlcf->cmds == NULL) {
@@ -595,6 +601,12 @@ ngx_http_headers_more_parse_directive(ngx_conf_t *cf, ngx_command_t *ngx_cmd,
                 replace = 1;
                 continue;
             }
+
+            if (arg[i].data[1] == 'a') {
+                dd("Found add only flag");
+                add_only = 1;
+                continue;
+            }
         }
 
         ngx_log_error(NGX_LOG_ERR, cf->log, 0,
@@ -615,6 +627,7 @@ ngx_http_headers_more_parse_directive(ngx_conf_t *cf, ngx_command_t *ngx_cmd,
         h = cmd->headers->elts;
         for (i = 0; i < cmd->headers->nelts; i++) {
             h[i].replace = replace;
+            h[i].add_only = add_only;
         }
     }
 
@@ -741,6 +754,11 @@ ngx_http_set_builtin_multi_header(ngx_http_request_t *r,
     headers = (ngx_array_t *) ((char *) &r->headers_in + hv->offset);
 
     if (headers->nelts > 0) {
+        if (hv->add_only) {
+            dd("skip multi-value headers because %s does set", hv->key.data);
+            return NGX_OK;
+        }
+
         ngx_array_destroy(headers);
 
         if (ngx_array_init(headers, r->pool, 2,

src/ngx_http_headers_more_headers_out.c

@@ -224,6 +224,12 @@ ngx_http_set_header_helper(ngx_http_request_t *r,
 
 matched:
 
+        if (hv->add_only) {
+            dd("skip because %s does set", hv->key.data);
+            matched = 1;
+            continue;
+        }
+
         if (value->len == 0 || matched) {
             dd("clearing normal header for %.*s", (int) hv->key.len,
                hv->key.data);
@@ -304,6 +310,11 @@ ngx_http_set_builtin_header(ngx_http_request_t *r,
         return ngx_http_set_header_helper(r, hv, value, old, 0);
     }
 
+    if (hv->add_only) {
+        dd("skip because %s does set", hv->key.data);
+        return NGX_OK;
+    }
+
     h = *old;
 
     if (value->len == 0) {
@@ -344,6 +355,11 @@ ngx_http_set_builtin_multi_header(ngx_http_request_t *r,
     /* override old values (if any) */
 
     if (pa->nelts > 0) {
+        if (hv->add_only) {
+            dd("skip because %s does set", hv->key.data);
+            return NGX_OK;
+        }
+
         ph = pa->elts;
         for (i = 1; i < pa->nelts; i++) {
             ph[i]->hash = 0;
@@ -565,16 +581,17 @@ static char *
 ngx_http_headers_more_parse_directive(ngx_conf_t *cf, ngx_command_t *ngx_cmd,
     void *conf, ngx_http_headers_more_opcode_t opcode)
 {
+    ngx_flag_t                         add_only = 0;
     ngx_http_headers_more_loc_conf_t  *hlcf = conf;
 
-    ngx_uint_t                         i;
-    ngx_http_headers_more_cmd_t       *cmd;
-    ngx_str_t                         *arg;
-    ngx_flag_t                         ignore_next_arg;
-    ngx_str_t                         *cmd_name;
-    ngx_int_t                          rc;
-
-    ngx_http_headers_more_main_conf_t  *hmcf;
+    ngx_str_t                           *arg;
+    ngx_str_t                           *cmd_name;
+    ngx_int_t                            rc;
+    ngx_flag_t                           ignore_next_arg;
+    ngx_uint_t                           i;
+    ngx_http_headers_more_cmd_t         *cmd;
+    ngx_http_headers_more_main_conf_t   *hmcf;
+    ngx_http_headers_more_header_val_t  *h;
 
     if (hlcf->cmds == NULL) {
         hlcf->cmds = ngx_array_create(cf->pool, 1,
@@ -680,6 +697,10 @@ ngx_http_headers_more_parse_directive(ngx_conf_t *cf, ngx_command_t *ngx_cmd,
                 ignore_next_arg = 1;
 
                 continue;
+
+            } else if (arg[i].data[1] == 'a') {
+                add_only = 1;
+                continue;
             }
         }
 
@@ -695,6 +716,13 @@ ngx_http_headers_more_parse_directive(ngx_conf_t *cf, ngx_command_t *ngx_cmd,
 
     if (cmd->headers->nelts == 0) {
         cmd->headers = NULL;
+
+    } else {
+        h = cmd->headers->elts;
+
+        for (i = 0; i < cmd->headers->nelts; i++) {
+            h[i].add_only = add_only;
+        }
     }
 
     if (cmd->types->nelts == 0) {

t/input.t

@@ -5,7 +5,7 @@ use Test::Nginx::Socket; # 'no_plan';
 
 repeat_each(2);
 
-plan tests => repeat_each() * 124;
+plan tests => repeat_each() * 142;
 
 no_long_string();
 #no_diff;
@@ -1289,3 +1289,113 @@ X-Forwarded-For: 8.8.8.8
 Foo: 127.0.0.1
 --- no_error_log
 [error]
+
+
+
+=== TEST 50: set request header if not set the header with -a option
+--- config
+    location /foo {
+        more_set_input_headers -a 'X-Foo: howdy';
+        echo "input_header: $http_x_foo";
+    }
+--- request
+    GET /foo
+--- response_body
+input_header: howdy
+
+
+
+=== TEST 51: do not set request header if set the header with -a option
+--- config
+    location /foo {
+        more_set_input_headers -a 'X-Foo: howdy';
+        content_by_lua '
+            local headers = ngx.req.get_headers()
+            ngx.say(headers["X-Foo"])
+        ';
+    }
+--- request
+    GET /foo
+--- more_headers
+X-Foo: blah
+
+--- response_body
+blah
+
+
+
+=== TEST 52: do not remove multi request header if set the header with -a option
+--- config
+    location /foo {
+        more_set_input_headers -a 'X-Foo: howdy';
+        content_by_lua '
+            local headers = ngx.req.get_headers()
+            ngx.say(headers["AAA"])
+        ';
+    }
+--- request
+    GET /foo
+--- more_headers
+AAA: blah
+AAA: baz
+
+--- response_body
+blahbaz
+
+
+
+=== TEST 53: test -a -t work together
+--- config
+    location /foo {
+        more_set_input_headers -a -t 'text/html' 'X-Foo: howdy';
+        content_by_lua '
+            local headers = ngx.req.get_headers()
+            ngx.say(headers["X-Foo"])
+        ';
+    }
+--- request
+    GET /foo
+--- more_headers
+Content-Type: text/html
+
+--- response_body
+howdy
+
+
+
+=== TEST 54: test -a -r work together
+--- config
+    location /foo {
+        more_set_input_headers -a -r 'X-Foo: howdy';
+        content_by_lua '
+            local headers = ngx.req.get_headers()
+            ngx.say(headers["X-Foo"])
+        ';
+    }
+--- request eval
+["GET /foo", "GET /foo"]
+--- more_headers eval
+["X-Foo: hi", ""]
+
+--- response_body eval
+["howdy\n", "howdy\n"]
+
+
+
+=== TEST 55: test -a -r -t work together
+--- config
+    location /foo {
+        more_set_input_headers -a -r -t 'text/html' 'X-Foo: howdy';
+        content_by_lua '
+            local headers = ngx.req.get_headers()
+            ngx.say(headers["X-Foo"])
+        ';
+    }
+--- request eval
+["GET /foo", "GET /foo", "GET /foo"]
+--- more_headers eval
+["Content-Type: text/html", "", "Content-Type: text/html\nX-Foo: hi\n"]
+
+--- response_body eval
+["howdy\n", "nil\n", "howdy\n"]
+