MagicChunks not writing web.config attribute - azure-devops

Question

I have this block in my web.config:
<rewrite>
<rules>
<rule name="Remove Trailing Slash" stopProcessing="false">
<match url="(.*)/$" />
<conditions>
<add input="{REQUEST_FILENAME}" matchType="IsDirectory" negate="true" />
<add input="{REQUEST_FILENAME}" matchType="IsFile" negate="true" />
</conditions>
<action type="Rewrite" url="{R:1}" />
</rule>
<rule name="Angular UI Router - HTML5 Mode" stopProcessing="true">
<match url=".*" />
<conditions logicalGrouping="MatchAll">
<add input="{REQUEST_FILENAME}" matchType="IsFile" negate="true" />
<add input="{REQUEST_FILENAME}" matchType="IsDirectory" negate="true" />
<add input="{URL}" pattern="/api/" negate="true" />
</conditions>
<action type="Rewrite" url="/app/" />
</rule>
</rules>
</rewrite>
In an Azure release pipeline I'm using the MagicChunks tool to transform the web.config to change the second action elements' url attribute to "/" but it is failing. The transform I have is:
{
"rewrite/rules/rule/action[#type='Rewrite' and #url='/app/']/#url": "/"
}
The error it throws up is:
System.ArgumentException:***There***is***empty***items***in***the***path.
How can I target an attribute to be transformed when it is not the attribute(s) being used as the target path?

Answer 1

Not sure how your web.config looks like, but there's something wrong with your transform syntax. Check document from that extension. You should use something like:
{
"rewrite/rules/rule[#name='Angular UI Router - HTML5 Mode']/action[#type='Rewrite']/#url": "/"
}
Since I tested your script in this way:
<?xml version="1.0" encoding="utf-8"?>
<configuration>
<system.web>
</system.web>
<rewrite>
...
</rewrite>
</configuration>
So I actually used something like:
{
"configuration/rewrite/rules/rule[#name='Angular UI Router - HTML5 Mode']/action[#type='Rewrite']/#url": "/"
}
Be careful about the root node in your web.config. Then it should work well to replace the url attribute to "/". Let me know if I misunderstand anything :)