Make const Env functions tolerant of NULL

This is convenient in places where you don't necessarily need an Env, since in
this case these methods work the same as if with an empty Env.

3 files changed, 17 insertions, 5 deletions

diff --git a/include/serd/serd.h b/include/serd/serd.h
index 79353e50..cfdc8693 100644
--- a/include/serd/serd.h
+++ b/include/serd/serd.h
@@ -1030,7 +1030,7 @@ serd_env_free(SerdEnv* SERD_NULLABLE env);
 /// Get the current base URI
 SERD_PURE_API
 const SerdNode* SERD_NULLABLE
-serd_env_base_uri(const SerdEnv* SERD_NONNULL env);
+serd_env_base_uri(const SerdEnv* SERD_NULLABLE env);
 
 /// Set the current base URI
 SERD_API
@@ -1058,7 +1058,7 @@ serd_env_set_prefix(SerdEnv* SERD_NONNULL env,
 */
 SERD_API
 SerdNode* SERD_ALLOCATED
-serd_env_qualify(const SerdEnv* SERD_NONNULL  env,
+serd_env_qualify(const SerdEnv* SERD_NULLABLE env,
                  const SerdNode* SERD_NONNULL uri);
 
 /**
@@ -1072,8 +1072,8 @@ serd_env_qualify(const SerdEnv* SERD_NONNULL  env,
 */
 SERD_API
 SerdNode* SERD_ALLOCATED
-serd_env_expand(const SerdEnv* SERD_NONNULL  env,
-                const SerdNode* SERD_NONNULL node);
+serd_env_expand(const SerdEnv* SERD_NULLABLE  env,
+                const SerdNode* SERD_NULLABLE node);
 
 /// Write all prefixes in `env` to `sink`
 SERD_API
diff --git a/src/env.c b/src/env.c
index 29df5286..49d2efa2 100644
--- a/src/env.c
+++ b/src/env.c
@@ -115,7 +115,7 @@ serd_env_base_uri_view(const SerdEnv* env)
 const SerdNode*
 serd_env_base_uri(const SerdEnv* env)
 {
-  return env->base_uri_node;
+  return env ? env->base_uri_node : NULL;
 }
 
 SerdStatus
@@ -202,6 +202,10 @@ serd_env_qualify_in_place(const SerdEnv*   env,
                           const SerdNode** prefix,
                           SerdStringView*  suffix)
 {
+  if (!env) {
+    return false;
+  }
+
   for (size_t i = 0; i < env->n_prefixes; ++i) {
     const SerdNode* const prefix_uri = env->prefixes[i].uri;
     if (uri->n_bytes >= prefix_uri->n_bytes) {
@@ -244,6 +248,10 @@ serd_env_expand_in_place(const SerdEnv*  env,
                          SerdStringView* uri_prefix,
                          SerdStringView* uri_suffix)
 {
+  if (!env) {
+    return SERD_ERR_BAD_CURIE;
+  }
+
   const char* const str   = serd_node_string(curie);
   const char* const colon = (const char*)memchr(str, ':', curie->n_bytes + 1);
   if (curie->type != SERD_CURIE || !colon) {
diff --git a/test/test_env.c b/test/test_env.c
index fcc45c53..651bf8c9 100644
--- a/test/test_env.c
+++ b/test/test_env.c
@@ -46,6 +46,10 @@ test_env(void)
 
   serd_env_set_prefix(env, prefix, eg);
 
+  assert(!serd_env_base_uri(NULL));
+  assert(!serd_env_expand(NULL, NULL));
+  assert(!serd_env_qualify(NULL, foo_u));
+
   assert(!serd_env_base_uri(env));
   assert(!serd_env_set_base_uri(env, SERD_EMPTY_STRING()));
   assert(!serd_env_base_uri(env));