PY-20203 Short RST headings missing in structure view.

python/python-rest/test/com/jetbrains/rest/RestLexerTest.java

@@ -123,6 +123,15 @@ public class RestLexerTest extends TestCase {
     );
   }
 
+  public void testShortHeading() throws IOException {
+    doTest("DSF\n" +
+           "===",
+           "[DSF, LINE]",
+           "[\n, WHITESPACE]",
+           "[===, LINE]"
+    );
+  }
+
   public void testInterpreted() throws IOException {
     doTest(":kbd:`1`\n" +
            "\n" +

python/rest/src/com/jetbrains/rest/lexer/rest.flex

@@ -19,7 +19,7 @@ CRLF=\R
 SPACE=[\ \t]
 
 ADORNMENT_SYMBOL="="|"-"|"`"|":"|"."|"'"|\"|"~"|"^"|"_"|"*"|"+"|"#"|">"
-ADORNMENT=("="{4, 80}|"-"{4, 80}|"`"{4, 80}|":"{4, 80}|"."{4, 80}|"'"{4, 80}|\"{4, 80}|"~"{4, 80}|"^"{4, 80}|"_"{4, 80}|"*"{4, 80}|"+"{4, 80}|"#"{4, 80})" "*{CRLF}
+ADORNMENT=("="+|"-"+|"`"+|":"+|"."+|"'"+|\"+|"~"+|"^"+|"_"+|"*"+|"+"+|"#"+)" "*{CRLF}
 SEPARATOR=[\n .:,()\{\}\[\]\-]
 USUAL_TYPES="attention"|"caution"|"danger"|"error"|"hint"|"important"|"note"|"tip"|"warning"|"admonition"|"image"|"figure"|"topic"|"sidebar"|"parsed-literal"|"rubric"|"epigraph"|"highlights"|"pull-quote"|"compound"|"container"|"table"|"csv-table"|"list-table"|"contents"|"sectnum"|"section-autonumbering"|"header"|"footer"|"target-notes"|"footnotes"|"citations"|"meta"|"replace"|"unicode"|"date"|"include"|"raw"|"class"|"role"|"default-role"|"title"|"restructuredtext-test-directive"
 HIGHLIGHT_TYPES= "highlight" | "sourcecode" | "code-block"