Python: Added "prefix" to configuration.

This patch gives users the option to set a `"prefix"` attribute
for Python applications, either at the top level or for specific
`"target"`s. If the attribute is present, the value of `"prefix"`
must be a string beginning with `"/"`. If the value of the `"prefix"`
attribute is longer than 1 character and ends in `"/"`, the
trailing `"/"` is stripped.

The purpose of the `"prefix"` attribute is to set the `SCRIPT_NAME`
context value for WSGI applications and the `root_path` context
value for ASGI applications, allowing applications to properly route
requests regardless of the path that the server uses to expose the
application.

The context value is only set if the request's URL path begins with
the value of the `"prefix"` attribute. In all other cases, the
`SCRIPT_NAME` or `root_path` values are not set. In addition, for
WSGI applications, the value of `"prefix"` will be stripped from
the beginning of the request's URL path before it is sent to the
application.

Reviewed-by: Andrei Zeliankou <zelenkov@nginx.com>
Reviewed-by: Artem Konev <artem.konev@nginx.com>
Signed-off-by: Alejandro Colomar <alx@nginx.com>

1 files changed, 37 insertions, 0 deletions

diff --git a/src/nxt_conf_validation.c b/src/nxt_conf_validation.c
index c6e63c25..bf8aa760 100644
--- a/src/nxt_conf_validation.c
+++ b/src/nxt_conf_validation.c
@@ -128,6 +128,8 @@ static nxt_int_t nxt_conf_vldt_python_path_element(nxt_conf_validation_t *vldt,
     nxt_conf_value_t *value);
 static nxt_int_t nxt_conf_vldt_python_protocol(nxt_conf_validation_t *vldt,
     nxt_conf_value_t *value, void *data);
+static nxt_int_t nxt_conf_vldt_python_prefix(nxt_conf_validation_t *vldt,
+    nxt_conf_value_t *value, void *data);
 static nxt_int_t nxt_conf_vldt_threads(nxt_conf_validation_t *vldt,
     nxt_conf_value_t *value, void *data);
 static nxt_int_t nxt_conf_vldt_thread_stack_size(nxt_conf_validation_t *vldt,
@@ -796,6 +798,11 @@ static nxt_conf_vldt_object_t  nxt_conf_vldt_python_members[] = {
         .validator  = nxt_conf_vldt_targets_exclusive,
         .u.string   = "callable",
     }, {
+        .name       = nxt_string("prefix"),
+        .type       = NXT_CONF_VLDT_STRING,
+        .validator  = nxt_conf_vldt_targets_exclusive,
+        .u.string   = "prefix",
+    }, {
         .name       = nxt_string("targets"),
         .type       = NXT_CONF_VLDT_OBJECT,
         .validator  = nxt_conf_vldt_targets,
@@ -814,6 +821,10 @@ static nxt_conf_vldt_object_t  nxt_conf_vldt_python_target_members[] = {
     }, {
         .name       = nxt_string("callable"),
         .type       = NXT_CONF_VLDT_STRING,
+    }, {
+        .name       = nxt_string("prefix"),
+        .type       = NXT_CONF_VLDT_STRING,
+        .validator  = nxt_conf_vldt_python_prefix,
     },
 
     NXT_CONF_VLDT_END
@@ -828,6 +839,10 @@ static nxt_conf_vldt_object_t  nxt_conf_vldt_python_notargets_members[] = {
     }, {
         .name       = nxt_string("callable"),
         .type       = NXT_CONF_VLDT_STRING,
+    }, {
+        .name       = nxt_string("prefix"),
+        .type       = NXT_CONF_VLDT_STRING,
+        .validator  = nxt_conf_vldt_python_prefix,
     },
 
     NXT_CONF_VLDT_NEXT(nxt_conf_vldt_python_common_members)
@@ -1871,6 +1886,28 @@ nxt_conf_vldt_python_protocol(nxt_conf_validation_t *vldt,
 
 
 static nxt_int_t
+nxt_conf_vldt_python_prefix(nxt_conf_validation_t *vldt,
+    nxt_conf_value_t *value, void *data)
+{
+    nxt_str_t  prefix;
+
+    if (nxt_conf_type(value) != NXT_CONF_STRING) {
+        return nxt_conf_vldt_error(vldt, "The \"prefix\" must be a string "
+                                   "beginning with \"/\".");
+    }
+
+    nxt_conf_get_string(value, &prefix);
+
+    if (!nxt_strchr_start(&prefix, '/')) {
+        return nxt_conf_vldt_error(vldt, "The \"prefix\" must be a string "
+                                   "beginning with \"/\".");
+    }
+
+    return NXT_OK;
+}
+
+
+static nxt_int_t
 nxt_conf_vldt_threads(nxt_conf_validation_t *vldt, nxt_conf_value_t *value,
     void *data)
 {