martin-g commented on a change in pull request #351:
URL: https://github.com/apache/tomcat/pull/351#discussion_r494077383
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File path: java/org/apache/jasper/compiler/NewlineReductionServletWriter.java
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@@ -0,0 +1,41 @@
+package org.apache.jasper.compiler;
+
+import java.io.PrintWriter;
+
+/**
+ * This class filters duplicate newlines instructions from the compiler output,
+ * and therefore from the runtime JSP. The duplicates typically happen because
+ * the compiler has multiple branches that write them, but they operate
+ * independently and don't realize that the previous output was identical.
+ *
+ * Removing these lines makes the JSP more efficient by executing fewer
operations during runtime.
+ *
+ * @author Engebretson, John
+ * @author Kamnani, Jatin
+ *
+ */
+public class NewlineReductionServletWriter extends ServletWriter {
+ private static final String NEWLINE_WRITE_TEXT = "out.write('\\n');";
Review comment:
This one is a bit strange.
I haven't written JSP code in more than 10 years now but if I want to
produce several new lines I'd do `out.write("\n\n\n\n")` instead of 4 times
`out.write('\\n');`.
In what cases one would have several `out.write('\\n');` ?
##########
File path: java/org/apache/jasper/compiler/Generator.java
##########
@@ -2095,6 +2101,20 @@ public void visit(Node.JspElement n) throws
JasperException {
public void visit(Node.TemplateText n) throws JasperException {
String text = n.getText();
+ // If the flag is active, attempt to minimize the frequency of
+ // regex operations.
+ if ((ctxt!=null) &&
+ ctxt.getOptions().getJSPWhiteSpaceTrimFlag() &&
+ text.contains("\n")) {
+ // Ensure there are no <pre> or </pre> tags embedded in this
+ // text - if there are, we want to NOT modify the whitespace.
+ Matcher preMatcher = PRE_TAG_PATTERN.matcher(text);
+ if (!preMatcher.matches()) {
+ Matcher matcher = BLANK_LINE_PATTERN.matcher(text);
+ String revisedText = matcher.replaceAll("\n");
Review comment:
This will drop also any `\r`s in the string. Is this intentional ?
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