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NPE in migration tool CopyResourcesStep

See original GitHub issue

Execution of the migration tool fails with the following exception at CopyResourcesStep:130

Caused by: java.lang.NullPointerException
at com.vaadin.flow.migration.CopyResourcesStep$HtmlImportRewriter.adjustContent (CopyResourcesStep.java:130)
at com.vaadin.flow.migration.CopyResourcesStep$HtmlImportRewriter.handle (CopyResourcesStep.java:84)
at com.vaadin.flow.migration.AbstractCopyResourcesStep$CopyFileVisitor.visitFile (AbstractCopyResourcesStep.java:88)
at com.vaadin.flow.migration.AbstractCopyResourcesStep$CopyFileVisitor.visitFile (AbstractCopyResourcesStep.java:68)
at java.nio.file.Files.walkFileTree (Files.java:2803)
at java.nio.file.Files.walkFileTree (Files.java:2875)
at com.vaadin.flow.migration.AbstractCopyResourcesStep.doCopyResources (AbstractCopyResourcesStep.java:186)
at com.vaadin.flow.migration.AbstractCopyResourcesStep.copyResources (AbstractCopyResourcesStep.java:178)
at com.vaadin.flow.migration.CopyResourcesStep.copyResources (CopyResourcesStep.java:191)
at com.vaadin.flow.migration.Migration.migrate (Migration.java:171)
at com.vaadin.flow.plugin.maven.MigrateMojo.execute (MigrateMojo.java:120)

No information is provided in the log about what file caused that.

Vaadin 14.1.17

Issue Analytics

State:
Created 4 years ago
Reactions:1
Comments:6 (6 by maintainers)

Top GitHub Comments

1reaction

mvysnycommented, May 5, 2021

Instead of closing as WON’T FIX, how about we help the customer and harden the sources of the migration tool?

Looking at CopyResourcesStep:130, the body variable is clearly null, which means that there is a html file which clearly has no body. If this can happen, simply return from the function. If this should not happen, add a simple check which will fail with an informative error message!

            if (body == null) {
                throw new IllegalArgumentException("File " + file + " has no <body> element");
            }

0reactions

mvysnycommented, May 5, 2021

Indeed, when I added the lines above, recompiled the migration tool on the 2.6 branch and ran it, the exception is now much more informative:

Exception in thread "main" java.lang.IllegalArgumentException: File ./src/main/webapp/frontend/flowgraph/node_modules/paper/dist/docs/index.html has no <body> element
	at com.vaadin.flow.migration.CopyResourcesStep$HtmlImportRewriter.adjustContent(CopyResourcesStep.java:113)
	at com.vaadin.flow.migration.CopyResourcesStep$HtmlImportRewriter.handle(CopyResourcesStep.java:84)
	at com.vaadin.flow.migration.AbstractCopyResourcesStep$CopyFileVisitor.visitFile(AbstractCopyResourcesStep.java:88)

The HTML file in question is:

<!DOCTYPE html>
<html>
<head>
<meta charset="UTF-8">
<title>Paper.js v0.12.0</title>
</head>
<frameset cols="230,*">
<frame src="classes/index.html" name="packageListFrame" title="All Packages">
<frame src="about:blank" name="class-frame" title="Class and interface descriptions">
</frameset>
</html>

It can be safely skipped. Indeed, this code does the trick:

            if (body == null) {
                System.out.println("Skipping " + file + " since it has no <body> element");
                return doc.outerHtml();
            }

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