GFENG-112153: additional validation rules for Gherkin Parser are added.

The following validations are covered:
- Missing 'Feature' keyword.
- Missing 'Scenario' or 'Scenario Outline' keywords.
- Missing any steps for scenario.
- Presence 'Examples' keyword for 'Scenario' block.
- Missing 'Examples' block for 'Scenario Outline' block.
- Presence of tags with spaces for 'Feature' and 'Scenario' blocks.
- Presence of 'AND' step strict after 'Scenario' line.
- Presence more than one 'Feature' block declaration.
- Presence tags between steps keywords.
- Presence steps between 'Feature' and 'Scenario' blocks.

Author: kochau

src/main/antlr4/com/pdsl/gherkin/parser/GherkinLexer.g4

@@ -111,6 +111,7 @@ fragment CAPTURE_DATA : '<' ~[>\t\r\n ]'>' ;
 fragment DOCSTRING_DOUBLE_QUOTES : WS* '"""' (CAPTURE_DATA | ~'"' | '"' ~'"')*?  '"""' LINE_END ;
 fragment DOCSTRING_BACKTICKS : WS* '```' (~'`' | CAPTURE_DATA | '`' ~'`').*? '```' LINE_END;
 fragment TAG : '@'~[ \r\n\t@]+ ;
+fragment TAG_WITH_SPACES: '@' (~[\r\n@ ]* ' ' ~[\r\n@ ]+);
 fragment ESCAPE_SEQUENCE : '\\' [\\|\n]* ;
 fragment CELL_CHARACTER
 	:	CAPTURE_DATA
@@ -120,6 +121,7 @@ fragment CELL_CHARACTER
 fragment CELL_DATA : WS* CELL_CHARACTER* '|';
 
 DOCSTRING : DOCSTRING_DOUBLE_QUOTES | DOCSTRING_BACKTICKS ;
+TAGS_WITH_SPACES : WS* TAG_WITH_SPACES (WS* TAG_WITH_SPACES)* (COMMENT? | LINE_END);
 TAGS : WS* TAG (WS* TAG)* (COMMENT? | LINE_END);
 FEATURE_TITLE : WS* FEATURE_KEYWORD ~[\r\n]* LINE_END ;
 BACKGROUND_TITLE : WS* BACKGROUND_KEYWORD ~[\r\n]* COMMENT? LINE_END ;

src/main/antlr4/com/pdsl/gherkin/parser/GherkinLexer.tokens

@@ -14,26 +14,27 @@ WILD_KEYWORD=13
 AND_KEYWORD=14
 BUT_KEYWORD=15
 DOCSTRING=16
-TAGS=17
-FEATURE_TITLE=18
-BACKGROUND_TITLE=19
-EXAMPLES_TITLE=20
-SCENARIO_TITLE=21
-SCENARIO_OUTLINE_TITLE=22
-RULE_TITLE=23
-GIVEN_STEP=24
-WHEN_STEP=25
-THEN_STEP=26
-AND_STEP=27
-BUT_STEP=28
-WILD_STEP=29
-DATA_ROW=30
-INVALID_LANGUAGE_HEADER=31
-COMMENT=32
-LINE_END=33
-NEWLINE=34
-WS=35
-LONG_DESCRIPTION=36
+TAGS_WITH_SPACES=17
+TAGS=18
+FEATURE_TITLE=19
+BACKGROUND_TITLE=20
+EXAMPLES_TITLE=21
+SCENARIO_TITLE=22
+SCENARIO_OUTLINE_TITLE=23
+RULE_TITLE=24
+GIVEN_STEP=25
+WHEN_STEP=26
+THEN_STEP=27
+AND_STEP=28
+BUT_STEP=29
+WILD_STEP=30
+DATA_ROW=31
+INVALID_LANGUAGE_HEADER=32
+COMMENT=33
+LINE_END=34
+NEWLINE=35
+WS=36
+LONG_DESCRIPTION=37
 'Scenario Outline:'=4
 'Background:'=5
 'Rule:'=7

src/main/antlr4/com/pdsl/gherkin/parser/GherkinParser.g4

@@ -11,6 +11,35 @@ ruleBlock : RULE_TITLE  LONG_DESCRIPTION*  background? scenario*;
 background : BACKGROUND_TITLE  LONG_DESCRIPTION*? stepBody? ;
 scenario : TAGS*? (SCENARIO_TITLE | SCENARIO_OUTLINE_TITLE) LONG_DESCRIPTION* stepBody? examplesBody*;
 stepBody :  startingStep  (anyStep)* ;
+
 examplesBody : TAGS*?  EXAMPLES_TITLE  LONG_DESCRIPTION*?  DATA_ROW* ;
 startingStep : (GIVEN_STEP | WHEN_STEP | THEN_STEP | WILD_STEP) (DATA_ROW* | DOCSTRING) ;
 anyStep : (GIVEN_STEP | WHEN_STEP | THEN_STEP | AND_STEP | BUT_STEP | WILD_STEP) (DATA_ROW* | DOCSTRING) ;
+
+fullFeatureBlock: LANGUAGE_HEADER? COMMENT* TAGS*? FEATURE_TITLE LONG_DESCRIPTION*?;
+
+validationMissingFeature : LANGUAGE_HEADER? COMMENT* TAGS*? LONG_DESCRIPTION*?;
+validationMissingScenario : fullFeatureBlock TAGS*? LONG_DESCRIPTION* stepBody? examplesBody*;
+vadalitionScenarioWithoutSteps: fullFeatureBlock TAGS*? (SCENARIO_TITLE | SCENARIO_OUTLINE_TITLE);
+validationPresenceExamplesForScenario: fullFeatureBlock TAGS*? SCENARIO_TITLE LONG_DESCRIPTION* stepBody? TAGS*? EXAMPLES_TITLE LONG_DESCRIPTION*?;
+validationMissingExamplesRowsForScenarioOutline: fullFeatureBlock TAGS*? SCENARIO_OUTLINE_TITLE LONG_DESCRIPTION* stepBody? TAGS*? EXAMPLES_TITLE;
+validationFeatureTagsWithSpaces: LANGUAGE_HEADER? COMMENT* TAGS_WITH_SPACES FEATURE_TITLE LONG_DESCRIPTION*?;
+validationScenarioTagsWithSpaces: fullFeatureBlock TAGS_WITH_SPACES SCENARIO_TITLE LONG_DESCRIPTION* stepBody?;
+validationAndAfterScenario: fullFeatureBlock TAGS*? (SCENARIO_TITLE | SCENARIO_OUTLINE_TITLE) LONG_DESCRIPTION* AND_STEP stepBody?;
+validationSeveralFeatureDeclaration: fullFeatureBlock fullFeatureBlock;
+validationTagsBetweenSteps: fullFeatureBlock TAGS*? (SCENARIO_TITLE | SCENARIO_OUTLINE_TITLE) startingStep TAGS+ (anyStep)*;
+validationStepsBetweenFeatureAndScenario: fullFeatureBlock stepBody TAGS*? (SCENARIO_TITLE | SCENARIO_OUTLINE_TITLE);
+
+validation : (
+    validationStepsBetweenFeatureAndScenario
+    | validationTagsBetweenSteps
+    | vadalitionScenarioWithoutSteps
+    | validationSeveralFeatureDeclaration
+    | validationScenarioTagsWithSpaces
+    | validationFeatureTagsWithSpaces
+    | validationPresenceExamplesForScenario
+    | validationMissingExamplesRowsForScenarioOutline
+    | validationAndAfterScenario
+    | validationMissingScenario
+    | validationMissingFeature
+);