Implement a function to turn absolute schema references into relative (…

…#1424)

Signed-off-by: Juan Cruz Viotti <[email protected]>

src/jsonschema/CMakeLists.txt

@@ -7,7 +7,8 @@ noa_library(NAMESPACE sourcemeta PROJECT jsontoolkit NAME jsonschema
   PRIVATE_HEADERS anchor.h bundle.h resolver.h
     walker.h reference.h frame.h error.h unevaluated.h keywords.h
   SOURCES jsonschema.cc default_walker.cc frame.cc
-    anchor.cc resolver.cc walker.cc bundle.cc unevaluated.cc
+    anchor.cc resolver.cc walker.cc bundle.cc
+    unevaluated.cc relativize.cc
     "${CMAKE_CURRENT_BINARY_DIR}/official_resolver.cc")
 
 if(JSONTOOLKIT_INSTALL)

src/jsonschema/include/sourcemeta/jsontoolkit/jsonschema.h

@@ -322,6 +322,42 @@ SOURCEMETA_JSONTOOLKIT_JSONSCHEMA_EXPORT
 auto schema_format_compare(const JSON::String &left, const JSON::String &right)
     -> bool;
 
+/// @ingroup jsonschema
+///
+/// Try to turn every possible absolute reference in a schema into a relative
+/// one. For example:
+///
+/// ```cpp
+/// #include <sourcemeta/jsontoolkit/json.h>
+/// #include <sourcemeta/jsontoolkit/jsonschema.h>
+/// #include <cassert>
+///
+/// sourcemeta::jsontoolkit::JSON document =
+///   sourcemeta::jsontoolkit::parse(R"JSON({
+///   "$id": "https://www.example.com/schema",
+///   "$schema": "https://json-schema.org/draft/2020-12/schema",
+///   "$ref": "https://www.example.com/another",
+/// })JSON");
+///
+/// sourcemeta::jsontoolkit::relativize(schema,
+///   sourcemeta::jsontoolkit::default_dialect,
+///   sourcemeta::jsontoolkit::official_resolver);
+///
+/// const sourcemeta::jsontoolkit::JSON expected =
+///   sourcemeta::jsontoolkit::parse(R"JSON({
+///   "$id": "https://www.example.com/schema",
+///   "$schema": "https://json-schema.org/draft/2020-12/schema",
+///   "$ref": "another",
+/// })JSON");
+///
+/// assert(document == expected);
+/// ```
+SOURCEMETA_JSONTOOLKIT_JSONSCHEMA_EXPORT
+auto relativize(
+    JSON &schema, const SchemaWalker &walker, const SchemaResolver &resolver,
+    const std::optional<std::string> &default_dialect = std::nullopt,
+    const std::optional<std::string> &default_id = std::nullopt) -> void;
+
 } // namespace sourcemeta::jsontoolkit
 
 #endif

src/jsonschema/relativize.cc

@@ -0,0 +1,43 @@
+#include <sourcemeta/jsontoolkit/jsonschema.h>
+
+namespace sourcemeta::jsontoolkit {
+
+auto relativize(JSON &schema, const SchemaWalker &walker,
+                const SchemaResolver &resolver,
+                const std::optional<std::string> &default_dialect,
+                const std::optional<std::string> &default_id) -> void {
+  Frame frame;
+  frame.analyse(schema, walker, resolver, default_dialect, default_id);
+
+  for (const auto &entry : frame.locations()) {
+    if (entry.second.type != Frame::LocationType::Resource &&
+        entry.second.type != Frame::LocationType::Subschema) {
+      continue;
+    }
+
+    auto &subschema{get(schema, entry.second.pointer)};
+    assert(is_schema(subschema));
+    if (!subschema.is_object()) {
+      continue;
+    }
+
+    const auto base{URI{entry.second.base}.canonicalize()};
+    for (const auto &property : subschema.as_object()) {
+      if (walker(property.first, frame.vocabularies(entry.second, resolver))
+                  .type != KeywordType::Reference ||
+          !property.second.is_string()) {
+        continue;
+      }
+
+      URI reference{property.second.to_string()};
+      reference.canonicalize();
+      reference.relative_to(base);
+
+      if (reference.is_relative()) {
+        subschema.assign(property.first, JSON{reference.recompose()});
+      }
+    }
+  }
+}
+
+} // namespace sourcemeta::jsontoolkit

test/jsonschema/CMakeLists.txt

@@ -83,6 +83,7 @@ add_executable(sourcemeta_jsontoolkit_jsonschema_unit
   jsonschema_error_test.cc
   jsonschema_keyword_iterator_test.cc
   jsonschema_official_resolver_test.cc
+  jsonschema_relativize_test.cc
   jsonschema_map_resolver_test.cc
   jsonschema_flat_file_resolver_test.cc
   jsonschema_format_test.cc)