comments schema for erlang

Summary:
add comments predicate to erlang schema
according to the [docs](https://www.internalfb.com/intern/staticdocs/glean/docs/schema/changing/) it should be backward compatible
www sync: D55924286

Reviewed By: phlalx

Differential Revision: D55917964

fbshipit-source-id: 753a00ceb8fba34bbd34cb4d363c5ef002823e45

glean/schema/source/codemarkup.angle

@@ -763,6 +763,9 @@ predicate EntityComments:
       { java = Decl } = Entity;
       codemarkup.java.JavaEntityDocumentation { Decl, File, Span };
       nothing = Text
+    ) | (
+      { erlang = Decl } = Entity;
+      codemarkup.erlang.ErlangEntityDocumentation { Decl, File, Span, Text}
     ) | (
       { fbthrift = Decl } = Entity;
       codemarkup.fbthrift.FbthriftEntityDocumentation { Decl, File, Span };

glean/schema/source/codemarkup.erlang.angle

@@ -92,4 +92,15 @@ predicate ErlangEntityInfo:
   { E, { kind = K, isAbstract = false } } where
   ErlangEntityKind { E, K }
 
+  predicate ErlangEntityDocumentation :
+  {
+    entity : code.erlang.Entity,
+    file : src.File,
+    span : src.ByteSpan,
+    text : maybe string,
+  }
+  { Entity, File, Span, Text } where
+  { decl = Decl } = Entity;
+  erlang.DeclarationComment { Decl1, File, Span, Text };
+  erlang.Declaration { func = Decl1 } = Decl
 }

glean/schema/source/erlang.angle

@@ -20,6 +20,14 @@ predicate FunctionDeclaration :
     span : src.ByteSpan,
   }
 
+predicate DeclarationComment:
+  {
+    declaration : FunctionDeclaration,
+    file : src.File,
+    span : src.ByteSpan,
+    text : maybe string,
+  }
+
 ## types
 
 type Declaration =