Fix punctuation in some algorithms (graphql#1067)

Author: yaacovCR

STYLE_GUIDE.md

@@ -55,3 +55,8 @@ hyphens) should be capitalized, with the following exceptions:
 All elements in hyphenated words follow the same rules, e.g. headings may
 contain `Non-Null`, `Context-Free`, `Built-in` (`in` is a preposition, so is not
 capitalized).
+
+## Lists
+
+Lists can be written as full sentences or as fragments. Algorithms that appear
+as lists, however, should be written in full sentences with proper punctuation.

spec/Section 2 -- Language.md

@@ -1120,7 +1120,7 @@ ListValue : [ Value+ ]
 - For each {Value+}
   - Let {value} be the result of evaluating {Value}.
   - Append {value} to {inputList}.
-- Return {inputList}
+- Return {inputList}.
 
 ### Input Object Values
 
@@ -1168,7 +1168,7 @@ ObjectValue : { ObjectField+ }
   - Let {name} be {Name} in {field}.
   - Let {value} be the result of evaluating {Value} in {field}.
   - Add a field to {inputObject} of name {name} containing value {value}.
-- Return {inputObject}
+- Return {inputObject}.
 
 ## Variables
 

spec/Section 3 -- Type System.md

@@ -354,7 +354,7 @@ IsInputType(type) :
   - Return IsInputType({unwrappedType})
 - If {type} is a Scalar, Enum, or Input Object type:
   - Return {true}
-- Return {false}
+- Return {false}.
 
 IsOutputType(type) :
 
@@ -363,7 +363,7 @@ IsOutputType(type) :
   - Return IsOutputType({unwrappedType})
 - If {type} is a Scalar, Object, Interface, Union, or Enum type:
   - Return {true}
-- Return {false}
+- Return {false}.
 
 ### Type Extensions
 

spec/Section 5 -- Validation.md

@@ -1014,7 +1014,7 @@ is a validation error if the target of a spread is not defined.
 
 - For each {fragmentDefinition} in the document:
   - Let {visited} be the empty set.
-  - {DetectFragmentCycles(fragmentDefinition, visited)}
+  - {DetectFragmentCycles(fragmentDefinition, visited)}.
 
 DetectFragmentCycles(fragmentDefinition, visited):
 
@@ -1023,7 +1023,7 @@ DetectFragmentCycles(fragmentDefinition, visited):
   - {visited} must not contain {spread}.
   - Let {nextVisited} be the set including {spread} and members of {visited}.
   - Let {nextFragmentDefinition} be the target of {spread}.
-  - {DetectFragmentCycles(nextFragmentDefinition, nextVisited)}
+  - {DetectFragmentCycles(nextFragmentDefinition, nextVisited)}.
 
 **Explanatory Text**
 

spec/Section 6 -- Execution.md

@@ -263,7 +263,7 @@ CreateSourceEventStream(subscription, schema, variableValues, initialValue):
   is unaffected if an alias is used.
 - Let {field} be the first entry in {fields}.
 - Let {argumentValues} be the result of {CoerceArgumentValues(subscriptionType,
-  field, variableValues)}
+  field, variableValues)}.
 - Let {fieldStream} be the result of running
   {ResolveFieldEventStream(subscriptionType, initialValue, fieldName,
   argumentValues)}.