Rewirte turns to redirect in app service virtual application

Question

Step to reproduce:

1. /site/wwwroot/web.config:

      <?xml version="1.0"?>
      <configuration>
          <system.webServer>
              <rewrite>
                  <rules>
                      <rule name="SPA Routes" stopProcessing="true">
                          <match url=".*" />
                          <conditions logicalGrouping="MatchAll">
                              <add input="{REQUEST_FILENAME}" matchType="IsFile" negate="true" />
                              <add input="{REQUEST_FILENAME}" matchType="IsDirectory" negate="true" />
                          </conditions>
                          <action type="Rewrite" url="/" />
                      </rule>
                  </rules>
              </rewrite>
          </system.webServer>
      </configuration>
   

   which effectively serves /site/wwwroot/index.html for all requests with unmatched path. i.e. a user will either get 200(uncached) or 304(cached) response from the app service.
2. 1. delete /site/wwwroot/web.config else the virtual application will not work(dunno why, but I'm fine with it because I don't have a "root" application to serve)
   2. in virtual application and directory add virtual application with /test as path and \site\test as the physical path.
   3. /site/test/web.config:

            <?xml version="1.0"?>
            <configuration>
                <system.webServer>
                    <rewrite>
                        <rules>
                            <rule name="SPA Routes" stopProcessing="true">
                                <match url=".*" />
                                <conditions logicalGrouping="MatchAll">
                                    <add input="{REQUEST_FILENAME}" matchType="IsFile" negate="true" />
                                    <add input="{REQUEST_FILENAME}" matchType="IsDirectory" negate="true" />
                                </conditions>
                                <action type="Rewrite" url="/test" />
                            </rule>
                        </rules>
                    </rewrite>
                </system.webServer>
            </configuration>
      

3. visit https://<appservcie>/test the virtual app seems to be working fine. But when I visit https://<appservcie>/test/anypath the app service actually returns a 301 redirect response to /test, unlike the behavior in 1.. And this behavior stops user from directly accessing one of those sub-routes in a single page application by forcing a user to start from the entry route(i.e. /test)

I could not find any documentation describing this behavior nor could I find a way to stop it.

Answer 1

Sharing the solution shared by @Shaun Chen with the community. Thanks for confirming and sharing the solution.

Scenario: WebApp hosted on an App Service. The application is configured to serve index.html for all requests with unmatched paths, either returning a 200 (uncached) or 304 (cached) response. Virtual application with /test as the path and \site\test as the physical path.

Issue: When visiting the URL https://<appservice>/test/anypath, the App Service returns a 301 redirect response to /test. This behavior is different from the root application and prevents users from directly accessing sub-routes in a single-page application, forcing them to start from the entry route (i.e., /test).

Things Tried:

1. You have configured the web.config in the root directory (/site/wwwroot/web.config) to serve index.html for all requests with unmatched paths.
2. You deleted /site/wwwroot/web.config because the virtual application would not work otherwise.
3. You added a virtual application with /test as the path and \site\test as the physical path in the virtual application and directory.
4. You configured the web.config in the test directory (/site/test/web.config) to rewrite URLs to /test.

Answer shared by @Shaun Chen.

Resolution :

Modifying/add the trailing slash rewrite URL.

Referenced URLs:

• IIS URL rewrite is redirecting instead
• IIS generates courtesy redirect when folder without trailing slash is requested

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Answer 2

Well, dumb me, it's actually an IIS question. I managed to resolve it, refer to:

https://stackoverflow.com/questions/27238757/iis-url-rewrite-is-redirecting-instead

https://www.betaarchive.com/wiki/index.php?title=Microsoft_KB_Archive/298408