Fixes Erroneous syntax highlighting of if construct with tags #204

Labels were only captured at the start and end of a statement.
Now we are also capturing them in between for if conditionals.

 The edits in the end in "named-control-constructs" are meant to
 correctly handle whitespaces which before they were placed as part of
 the group returned to the invalid.error.xxx

 A unittest has been added testing the conditionals with/out labels.

Author: gnikit

CHANGELOG.md

@@ -25,6 +25,8 @@ and this project adheres to [Semantic Versioning](http://semver.org/).
 - Fixes the general preprocessor syntax highlighting and adds testing
 - Fixes using function/subroutine as parameter in functions/subroutines
   ([#207](https://github.com/krvajal/vscode-fortran-support/issues/207))
+- Fixes labelled conditionals erroneous highlighting
+  ([#204](https://github.com/krvajal/vscode-fortran-support/issues/204))
 
 ### Added
 

syntaxes/fortran_free-form.tmLanguage.json

@@ -17,7 +17,6 @@
 		"FPP",
 		".pf",
 		".PF"
-
 	],
 	"firstLineMatch": "(?i)-[*]- mode: fortran free -[*]-",
 	"injections": {
@@ -1353,7 +1352,7 @@
 			"comment": "Introduced in the Fortran 1990 standard.",
 			"contentName": "meta.named-construct.fortran.modern",
 			"begin": "(?ix)([a-z]\\w*)\\s*(:)(?=\\s*(?:associate|block(?!\\s*data)|critical|do|forall|if|select\\s*case|select\\s*type|select\\s*rank|where)\\b)",
-			"end": "(?i)\\s*(?!\\b(?:associate|block(?!\\s*data)|critical|do|forall|if|select\\s*case|select\\s*type|select\\s*rank|where)\\b)\\b(?:\\b(\\1)\\b)?(?:\\s*([^\\s;!][^;!\\n]*?))?(?=\\s*[;!\\n])",
+			"end": "(?i)(?!\\s*\\b(?:associate|block(?!\\s*data)|critical|do|forall|if|select\\s*case|select\\s*type|select\\s*rank|where)\\b)(?:\\b(\\1)\\b)?(?:\\s*([^\\s;!][^;!\\n]*?))?(?=\\s*[;!\\n])",
 			"endCaptures": {
 				"2": {
 					"name": "invalid.error.named-control-constructs.fortran.modern"
@@ -1611,10 +1610,14 @@
 											"include": "#parentheses"
 										},
 										{
-											"match": "(?i)\\b(then)\\b",
+											"comment": "capture the label if present",
+											"match": "(?i)\\b(then)\\b(\\s*[a-z]\\w*)?",
 											"captures": {
 												"1": {
 													"name": "keyword.control.then.fortran"
+												},
+												"2": {
+													"name": "meta.label.elseif"
 												}
 											}
 										},
@@ -1638,6 +1641,15 @@
 											"begin": "(?!(\\s*(;|!|\\n)))",
 											"end": "(?=[;!\\n])",
 											"patterns": [
+												{
+													"comment": "capture the label if present",
+													"match": "\\s*([a-z]\\w*)?\\s*",
+													"captures": {
+														"1": {
+															"name": "meta.label.else"
+														}
+													}
+												},
 												{
 													"include": "#invalid-word"
 												}

test/resources/conditionals.f90

@@ -0,0 +1,41 @@
+! if
+if (1 > 2) then
+end if
+
+! if-else
+if (1 > 2) then
+else
+end if
+
+! if-else-if-else
+if (1 > 2) then
+else if (2 < 1) then
+else
+end if
+
+! labelled if
+label1: if (1 > 2) then
+end if label1
+
+! labelled if-else
+label2: if (1 > 2) then
+else label2
+end if label2
+
+! labelled if-else-if-else
+label3: if (1 > 2) then
+else if (2 < 1) then label3
+else label3
+end if label3
+
+! labelled if with whitespace after end label
+label4: if (1 > 2) then
+end if  label4   ! bug continuous to new line
+
+! nested labels with whitespaces
+if (1 > 2) then
+   label5: if (1) then
+   end if label5 !
+else
+! whitespace in the "end if label5 " causes else to be incorrect
+end if