HttpModule could be placed under the location element

[lmolkova]

ApplicationInsights previously had issues with HttpModule installation if in custom web.config, system.webServer was added under the location element.

They came up with a following solution:

<?xml version="1.0"?>
<configuration xmlns:xdt="http://schemas.microsoft.com/XML-Document-Transform">
  <!-- Insert global system.web node in any case -->
  <system.web xdt:Transform="InsertIfMissing">
  </system.web>

  <!-- Search for system.web nodes:
        - globally
        - under location[@path='.']
        - under location[count(@path)=0]
        If any of above contains httpModules section - it will be reused. 
        Otherwise it will be created under /configuration/system.web (globally)
  -->
    <!-- Insert global system.web node in any case -->
  <system.webServer xdt:Transform="InsertIfMissing">
  </system.webServer>

  <!-- Only one validation node is allowed to be deinfed globally or in global location tags. See explanaition above for httpModules on how it works -->
  <system.webServer xdt:Locator="XPath(//system.webServer[(count(parent::location) = 0) or (count(parent::location[@path != '.' and count(@path) != 0]) = 0)])">
    <validation validateIntegratedModeConfiguration="false" xdt:Transform="InsertIfMissing" />
  </system.webServer>

  <!-- Only one modules node is allowed to be deinfed globally or in global location tags. 
       Modules node may not be defined in the same place where validation node above is defined.
       We need to remove all customer-renamed modules as remove tag relies on module name attribute
       See explanaition above for httpModules on how it works
  -->
  <system.webServer xdt:Locator="XPath(//system.webServer[(count(parent::location) = 0) or (count(parent::location[@path != '.' and count(@path) != 0]) = 0)])">
    <modules xdt:Transform="InsertIfMissing">
      <remove name="ApplicationInsightsWebTracking" xdt:Transform="InsertIfMissing" xdt:Locator="Match(name)"/>
      <add name="ApplicationInsightsWebTracking" type="Microsoft.ApplicationInsights.Web.ApplicationInsightsHttpModule, Microsoft.AI.Web" preCondition="managedHandler" xdt:Transform="Remove" xdt:Locator="Match(type)"/>
      <add name="ApplicationInsightsWebTracking" type="Microsoft.ApplicationInsights.Web.ApplicationInsightsHttpModule, Microsoft.AI.Web" preCondition="managedHandler" xdt:Transform="InsertIfMissing" xdt:Locator="Match(type)"/>
    </modules>
  </system.webServer>
</configuration>

They also have automated tests to verify installation.

1. We need to evaluate this approach and make sure TelemetryCorrelation module follows it
2. Reuse AppInsights automated tests for TelemetryCorrelation module

[lmolkova]

Remove module if it was added globally