grammar : support array references in json schema (#16792)

* grammar : support array references in json schema

* Update json-schema-to-grammar.cpp

Co-authored-by: Sigbjørn Skjæret <[email protected]>

* grammar : improve regex when naming ref derived rules

* grammar : replace non-conformant definitions array with anyOf test case

---------

Co-authored-by: Sigbjørn Skjæret <[email protected]>

Author: aldehir

common/json-schema-to-grammar.cpp

@@ -601,7 +601,10 @@ class SchemaConverter {
     }
 
     std::string _resolve_ref(const std::string & ref) {
-        std::string ref_name = ref.substr(ref.find_last_of('/') + 1);
+        auto it = ref.find('#');
+        std::string ref_fragment = it != std::string::npos ? ref.substr(it + 1) : ref;
+        static const std::regex nonalphanumeric_regex(R"([^a-zA-Z0-9-]+)");
+        std::string ref_name = "ref" + std::regex_replace(ref_fragment, nonalphanumeric_regex, "-");
         if (_rules.find(ref_name) == _rules.end() && _refs_being_resolved.find(ref) == _refs_being_resolved.end()) {
             _refs_being_resolved.insert(ref);
             json resolved = _refs[ref];
@@ -774,11 +777,24 @@ class SchemaConverter {
                         std::vector<std::string> tokens = string_split(pointer, "/");
                         for (size_t i = 1; i < tokens.size(); ++i) {
                             std::string sel = tokens[i];
-                            if (target.is_null() || !target.contains(sel)) {
+                            if (target.is_object() && target.contains(sel)) {
+                                target = target[sel];
+                            } else if (target.is_array()) {
+                                size_t sel_index;
+                                try {
+                                    sel_index = std::stoul(sel);
+                                } catch (const std::invalid_argument & e) {
+                                    sel_index = target.size();
+                                }
+                                if (sel_index >= target.size()) {
+                                    _errors.push_back("Error resolving ref " + ref + ": " + sel + " not in " + target.dump());
+                                    return;
+                                }
+                                target = target[sel_index];
+                            } else {
                                 _errors.push_back("Error resolving ref " + ref + ": " + sel + " not in " + target.dump());
                                 return;
                             }
-                            target = target[sel];
                         }
                         _refs[ref] = target;
                     }

examples/json_schema_to_grammar.py

@@ -371,8 +371,17 @@ def visit(n: dict):
                         raise ValueError(f'Unsupported ref {ref}')
 
                     for sel in ref.split('#')[-1].split('/')[1:]:
-                        assert target is not None and sel in target, f'Error resolving ref {ref}: {sel} not in {target}'
-                        target = target[sel]
+                        assert target is not None, f'Error resolving ref {ref}: {sel} not in {target}'
+                        if isinstance(target, list):
+                            try:
+                                sel_index = int(sel)
+                            except ValueError:
+                                raise ValueError(f'Error resolving ref {ref}: {sel} not in {target}')
+                            assert 0 <= sel_index < len(target), f'Error resolving ref {ref}: {sel} not in {target}'
+                            target = target[sel_index]
+                        else:
+                            assert sel in target, f'Error resolving ref {ref}: {sel} not in {target}'
+                            target = target[sel]
 
                     self._refs[ref] = target
                 else:
@@ -547,7 +556,8 @@ def join_seq():
 
 
     def _resolve_ref(self, ref):
-        ref_name = ref.split('/')[-1]
+        ref_fragment = ref.split('#')[-1]
+        ref_name = 'ref' + re.sub(r'[^a-zA-Z0-9-]+', '-', ref_fragment)
         if ref_name not in self._rules and ref not in self._refs_being_resolved:
             self._refs_being_resolved.add(ref)
             resolved = self._refs[ref]

tests/test-json-schema-to-grammar.cpp

@@ -1124,9 +1124,9 @@ static void test_all(const std::string & lang, std::function<void(const TestCase
         })""",
         R"""(
             char ::= [^"\\\x7F\x00-\x1F] | [\\] (["\\bfnrt] | "u" [0-9a-fA-F]{4})
-            foo ::= "{" space foo-a-kv "}" space
-            foo-a-kv ::= "\"a\"" space ":" space string
-            root ::= foo
+            ref-definitions-foo ::= "{" space ref-definitions-foo-a-kv "}" space
+            ref-definitions-foo-a-kv ::= "\"a\"" space ":" space string
+            root ::= ref-definitions-foo
             space ::= | " " | "\n"{1,2} [ \t]{0,20}
             string ::= "\"" char* "\"" space
         )"""
@@ -1151,20 +1151,58 @@ static void test_all(const std::string & lang, std::function<void(const TestCase
             "type": "object"
         })""",
         R"""(
-            alternative-0 ::= foo
-            alternative-1 ::= bar
-            bar ::= "{" space  (bar-b-kv )? "}" space
-            bar-b-kv ::= "\"b\"" space ":" space number
+            alternative-0 ::= ref-definitions-foo
+            alternative-1 ::= ref-definitions-bar
             decimal-part ::= [0-9]{1,16}
-            foo ::= "{" space  (foo-a-kv )? "}" space
-            foo-a-kv ::= "\"a\"" space ":" space number
             integral-part ::= [0] | [1-9] [0-9]{0,15}
             number ::= ("-"? integral-part) ("." decimal-part)? ([eE] [-+]? integral-part)? space
+            ref-definitions-bar ::= "{" space  (ref-definitions-bar-b-kv )? "}" space
+            ref-definitions-bar-b-kv ::= "\"b\"" space ":" space number
+            ref-definitions-foo ::= "{" space  (ref-definitions-foo-a-kv )? "}" space
+            ref-definitions-foo-a-kv ::= "\"a\"" space ":" space number
             root ::= alternative-0 | alternative-1
             space ::= | " " | "\n"{1,2} [ \t]{0,20}
         )"""
     });
 
+    test({
+        SUCCESS,
+        "anyOf $ref",
+        R"""({
+            "properties": {
+                "a": {
+                    "anyOf": [
+                        {"type": "string"},
+                        {"type": "number"}
+                    ]
+                },
+                "b": {
+                    "anyOf": [
+                        {"$ref": "#/properties/a/anyOf/0"},
+                        {"type": "boolean"}
+                    ]
+                }
+            },
+            "type": "object"
+        })""",
+        R"""(
+            a ::= string | number
+            a-kv ::= "\"a\"" space ":" space a
+            a-rest ::= ( "," space b-kv )?
+            b ::= b-0 | boolean
+            b-0 ::= string
+            b-kv ::= "\"b\"" space ":" space b
+            boolean ::= ("true" | "false") space
+            char ::= [^"\\\x7F\x00-\x1F] | [\\] (["\\bfnrt] | "u" [0-9a-fA-F]{4})
+            decimal-part ::= [0-9]{1,16}
+            integral-part ::= [0] | [1-9] [0-9]{0,15}
+            number ::= ("-"? integral-part) ("." decimal-part)? ([eE] [-+]? integral-part)? space
+            root ::= "{" space  (a-kv a-rest | b-kv )? "}" space
+            space ::= | " " | "\n"{1,2} [ \t]{0,20}
+            string ::= "\"" char* "\"" space
+        )"""
+    });
+
     test({
         SUCCESS,
         "mix of allOf, anyOf and $ref (similar to https://json.schemastore.org/tsconfig.json)",

tools/server/public_legacy/json-schema-to-grammar.mjs

@@ -345,10 +345,14 @@ export class SchemaConverter {
 
           const selectors = ref.split('#')[1].split('/').slice(1);
           for (const sel of selectors) {
-            if (!target || !(sel in target)) {
+            const selIndex = parseInt(sel, 10);
+            if (target && sel in target) {
+              target = target[sel];
+            } else if (target && selIndex in target) {
+              target = target[selIndex];
+            } else {
               throw new Error(`Error resolving ref ${ref}: ${sel} not in ${JSON.stringify(target)}`);
             }
-            target = target[sel];
           }
 
           this._refs[ref] = target;
@@ -594,7 +598,8 @@ export class SchemaConverter {
   }
 
   _resolveRef(ref) {
-    let refName = ref.split('/').pop();
+    let refFragment = ref.split('#').pop();
+    let refName = 'ref' + refFragment.replace(/[^a-zA-Z0-9-]+/g, '-');
     if (!(refName in this._rules) && !this._refsBeingResolved.has(ref)) {
       this._refsBeingResolved.add(ref);
       const resolved = this._refs[ref];