Don't treat missing value of one value keyword as an error

Since missing value might lead to StopIteration exception for now
let's just allow that value to be missing. Previously it'd stop
formating of remaining files in the batch. More details: PEP 479

Although it's an issue with incorrect CMake code rather than
parsing/formatting such code nevertheless it'd be more of an annoyance
in that case

CHANGELOG.md

@@ -1,5 +1,10 @@
 # Changelog
 
+## [0.2.1] 2020-06-20
+
+### Fixed
+- Missing value for one value keyword no longer leads to stopping formatting of remaining files in the batch
+
 ## [0.2.0] 2020-06-14
 
 ### Added

gersemi/__version__.py

@@ -4,4 +4,4 @@
 __license__ = "MPL 2.0"
 __title__ = "gersemi"
 __url__ = "https://github.com/BlankSpruce/gersemi"
-__version__ = "0.2.0"
+__version__ = "0.2.1"

gersemi/command_invocation_dumpers/argument_aware_command_invocation_dumper.py

@@ -67,7 +67,11 @@ def _split_by_keywords(self, arguments: Nodes) -> Tuple[Iterator[Nodes], Nodes]:
                 groups += [[argument]]
             elif is_one_of_one_value_keywords(argument):
                 groups += [pop_all(accumulator)]
-                groups += [[argument, next(iterator)]]
+                next_argument = next(iterator, None)
+                if next_argument is None:
+                    groups += [[argument]]
+                else:
+                    groups += [[argument, next_argument]]
             elif is_one_of_multi_value_keywords(argument):
                 groups += [pop_all(accumulator)]
                 accumulator = [argument]

tests/formatter/missing_value_for_one_value_keyword_is_not_an_error.in.cmake

@@ -0,0 +1,3 @@
+try_compile(FOO BAR BAZ OUTPUT_VARIABLE)
+
+try_compile(FOO__________________________________________________ BAR__________________________________________________ BAZ__________________________________________________ OUTPUT_VARIABLE)

tests/formatter/missing_value_for_one_value_keyword_is_not_an_error.out.cmake

@@ -0,0 +1,8 @@
+try_compile(FOO BAR BAZ OUTPUT_VARIABLE)
+
+try_compile(
+    FOO__________________________________________________
+    BAR__________________________________________________
+    BAZ__________________________________________________
+    OUTPUT_VARIABLE
+)