feat: suggest to encode disallowed URI Template characters

ext/snowcrash/src/UriTemplateParser.cc

@@ -21,6 +21,7 @@ namespace error_locator
 
     struct state {
         std::string message;
+        std::string encoded;
         size_t position = 0;
         size_t length = 0;
     };
@@ -59,6 +60,15 @@ namespace error_locator
     template <typename Rule>
     struct report_action : pegtl::nothing<Rule> {};
 
+    std::string encodeString(const std::string& in) {
+        std::stringstream encoded;
+        encoded << std::hex << std::uppercase;
+        for (const unsigned char chr : in) {
+            encoded << "%" << int(chr);
+        }
+        return encoded.str();
+    }
+
     template <>
     struct report_action<invalid_char>
     {
@@ -74,6 +84,7 @@ namespace error_locator
                 s.message = std::string{"character '"} + in.string() + std::string{"'"};
             }
 
+            s.encoded = std::move(encodeString(in.string()));
         }
     };
 
@@ -119,8 +130,13 @@ namespace
 
         std::stringstream ss;
         ss << "URI template variable '" << s.content
-           << "' contains invalid " << state.message
-           <<". Allowed characters for expressions are A-Z a-z 0-9 _ and percent encoded characters";
+           << "' contains invalid " << state.message;
+
+        if (!state.encoded.empty()) {
+            ss << ", which should be encoded as '" << state.encoded << "'";
+        }
+
+        ss <<". Allowed characters for expressions are A-Z a-z 0-9 _ and percent encoded characters";
 
 #if 0
         /**

ext/snowcrash/test/test-UriTemplateParser.cc

@@ -55,7 +55,7 @@ TEST_CASE("Parse uri template for invalid format curly brackets (nested brackets
     parser.parse(uri, sourceBlock, result);
 
     REQUIRE(result.report.warnings.size() == 2);
-    CHECK(result.report.warnings[0].message == "URI template variable 'id{' contains invalid nested expression brace '{'. Allowed characters for expressions are A-Z a-z 0-9 _ and percent encoded characters");
+    CHECK(result.report.warnings[0].message == "URI template variable 'id{' contains invalid nested expression brace '{', which should be encoded as '%7B'. Allowed characters for expressions are A-Z a-z 0-9 _ and percent encoded characters");
     CHECK(result.report.warnings[1].message == "URI template contains disallowed character '}'. Disallowed characters must be percent encoded.");
 }
 
@@ -238,7 +238,7 @@ TEST_CASE(
     parser.parse(uri, sourceBlock, result);
 
     REQUIRE(result.report.warnings.size() == 1);
-    REQUIRE(result.report.warnings[0].message == "URI template variable ' vartwo' contains invalid character ' '. Allowed characters for expressions are A-Z a-z 0-9 _ and percent encoded characters");
+    REQUIRE(result.report.warnings[0].message == "URI template variable ' vartwo' contains invalid character ' ', which should be encoded as '%20'. Allowed characters for expressions are A-Z a-z 0-9 _ and percent encoded characters");
 }
 
 TEST_CASE("Parse uri template for invalid variable name, contains hyphens",
@@ -253,8 +253,8 @@ TEST_CASE("Parse uri template for invalid variable name, contains hyphens",
     parser.parse(uri, sourceBlock, result);
 
     REQUIRE(result.report.warnings.size() == 2);
-    REQUIRE(result.report.warnings[0].message == "URI template variable 'var-one' contains invalid character '-'. Allowed characters for expressions are A-Z a-z 0-9 _ and percent encoded characters");
-    REQUIRE(result.report.warnings[1].message == "URI template variable 'var-two' contains invalid character '-'. Allowed characters for expressions are A-Z a-z 0-9 _ and percent encoded characters");
+    REQUIRE(result.report.warnings[0].message == "URI template variable 'var-one' contains invalid character '-', which should be encoded as '%2D'. Allowed characters for expressions are A-Z a-z 0-9 _ and percent encoded characters");
+    REQUIRE(result.report.warnings[1].message == "URI template variable 'var-two' contains invalid character '-', which should be encoded as '%2D'. Allowed characters for expressions are A-Z a-z 0-9 _ and percent encoded characters");
 }
 
 TEST_CASE("Parse uri template for invalid variable name, contains assignment",
@@ -269,7 +269,7 @@ TEST_CASE("Parse uri template for invalid variable name, contains assignment",
     parser.parse(uri, sourceBlock, result);
 
     REQUIRE(result.report.warnings.size() == 1);
-    REQUIRE(result.report.warnings[0].message == "URI template variable 'varone=vartwo' contains invalid character '='. Allowed characters for expressions are A-Z a-z 0-9 _ and percent encoded characters");
+    REQUIRE(result.report.warnings[0].message == "URI template variable 'varone=vartwo' contains invalid character '=', which should be encoded as '%3D'. Allowed characters for expressions are A-Z a-z 0-9 _ and percent encoded characters");
 }
 
 TEST_CASE("Parse uri template for invalid variable name, invalid % encoded",
@@ -299,7 +299,7 @@ TEST_CASE("Parse uri template for invalid variable name, invalid % encoded with
     parser.parse(uri, sourceBlock, result);
 
     REQUIRE(result.report.warnings.size() == 1);
-    REQUIRE(result.report.warnings[0].message == "URI template variable 'varone%2' contains invalid character '%'. Allowed characters for expressions are A-Z a-z 0-9 _ and percent encoded characters");
+    REQUIRE(result.report.warnings[0].message == "URI template variable 'varone%2' contains invalid character '%', which should be encoded as '%25'. Allowed characters for expressions are A-Z a-z 0-9 _ and percent encoded characters");
 }
 
 TEST_CASE("Parse uri template for variable name containing dot", "[validvariablenamecontainingdot][issue][78]")
@@ -343,7 +343,7 @@ TEST_CASE("Parse uri template for consistent invalid character warning",
     parser.parse(urione, sourceBlock, result);
 
     REQUIRE(result.report.warnings.size() == 1);
-    REQUIRE(result.report.warnings[0].message == "URI template variable '$a' contains invalid character '$'. Allowed characters for expressions are A-Z a-z 0-9 _ and percent encoded characters");
+    REQUIRE(result.report.warnings[0].message == "URI template variable '$a' contains invalid character '$', which should be encoded as '%24'. Allowed characters for expressions are A-Z a-z 0-9 _ and percent encoded characters");
 
 }
 
@@ -358,5 +358,5 @@ TEST_CASE("Parse uri template for variable name containing multibyte utf-8 char"
     parser.parse(uri, sourceBlock, result);
 
     REQUIRE(result.report.warnings.size() == 1);
-    REQUIRE(result.report.warnings[0].message == "URI template variable 'var荒data' contains invalid character '荒'. Allowed characters for expressions are A-Z a-z 0-9 _ and percent encoded characters");
+    REQUIRE(result.report.warnings[0].message == "URI template variable 'var荒data' contains invalid character '荒', which should be encoded as '%E8%8D%92'. Allowed characters for expressions are A-Z a-z 0-9 _ and percent encoded characters");
 }

test/fixtures/api/issue-702.json

@@ -263,7 +263,7 @@
           ]
         }
       },
-      "content": "URI template variable 'instance-id' contains invalid character '-'. Allowed characters for expressions are A-Z a-z 0-9 _ and percent encoded characters"
+      "content": "URI template variable 'instance-id' contains invalid character '-', which should be encoded as '%2D'. Allowed characters for expressions are A-Z a-z 0-9 _ and percent encoded characters"
     },
     {
       "element": "annotation",

test/fixtures/mson/issue-713.json

@@ -251,7 +251,7 @@
           ]
         }
       },
-      "content": "URI template variable 'a&b' contains invalid character '&'. Allowed characters for expressions are A-Z a-z 0-9 _ and percent encoded characters"
+      "content": "URI template variable 'a&b' contains invalid character '&', which should be encoded as '%26'. Allowed characters for expressions are A-Z a-z 0-9 _ and percent encoded characters"
     }
   ]
 }