@Import in CSS causes error on startup

[ggecy]

When starting application which imports JS Module containing CSS where there is the following line inside @import url('https://fonts.googleapis.com/css?family=Montserrat:700'); the following exception is thrown

java.lang.IllegalStateException: Failed to update the Flow imports file project_dir\target\frontend\generated-flow-imports.js'
at com.vaadin.flow.server.frontend.TaskUpdateImports.execute(TaskUpdateImports.java:100) ~[flow-server-2.0.2.jar:2.0.2]
at java.base/java.util.ArrayList.forEach(ArrayList.java:1540) ~[na:na]
at com.vaadin.flow.server.frontend.NodeTasks.execute(NodeTasks.java:303) ~[flow-server-2.0.2.jar:2.0.2]
at com.vaadin.flow.server.startup.DevModeInitializer.initDevModeHandler(DevModeInitializer.java:204) ~[flow-server-2.0.2.jar:2.0.2]
at com.vaadin.flow.spring.VaadinServletContextInitializer$DevModeServletContextListener.contextInitialized(VaadinServletContextInitializer.java:284) ~[vaadin-spring-12.0.2.jar:na]
at org.apache.catalina.core.StandardContext.listenerStart(StandardContext.java:4680) ~[tomcat-embed-core-9.0.17.jar:9.0.17]
at org.apache.catalina.core.StandardContext.startInternal(StandardContext.java:5150) ~[tomcat-embed-core-9.0.17.jar:9.0.17]
at org.apache.catalina.util.LifecycleBase.start(LifecycleBase.java:183) ~[tomcat-embed-core-9.0.17.jar:9.0.17]
at org.apache.catalina.core.ContainerBase$StartChild.call(ContainerBase.java:1377) ~[tomcat-embed-core-9.0.17.jar:9.0.17]
at org.apache.catalina.core.ContainerBase$StartChild.call(ContainerBase.java:1367) ~[tomcat-embed-core-9.0.17.jar:9.0.17]
at java.base/java.util.concurrent.FutureTask.run$$$capture(FutureTask.java:264) ~[na:na]
at java.base/java.util.concurrent.FutureTask.run(FutureTask.java) ~[na:na]
at org.apache.tomcat.util.threads.InlineExecutorService.execute(InlineExecutorService.java:75) ~[tomcat-embed-core-9.0.17.jar:9.0.17]
at java.base/java.util.concurrent.AbstractExecutorService.submit(AbstractExecutorService.java:140) ~[na:na]
at org.apache.catalina.core.ContainerBase.startInternal(ContainerBase.java:902) ~[tomcat-embed-core-9.0.17.jar:9.0.17]
at org.apache.catalina.core.StandardHost.startInternal(StandardHost.java:831) ~[tomcat-embed-core-9.0.17.jar:9.0.17]
at org.apache.catalina.util.LifecycleBase.start(LifecycleBase.java:183) ~[tomcat-embed-core-9.0.17.jar:9.0.17]
at org.apache.catalina.core.ContainerBase$StartChild.call(ContainerBase.java:1377) ~[tomcat-embed-core-9.0.17.jar:9.0.17]
at org.apache.catalina.core.ContainerBase$StartChild.call(ContainerBase.java:1367) ~[tomcat-embed-core-9.0.17.jar:9.0.17]
at java.base/java.util.concurrent.FutureTask.run$$$capture(FutureTask.java:264) ~[na:na]
at java.base/java.util.concurrent.FutureTask.run(FutureTask.java) ~[na:na]
at org.apache.tomcat.util.threads.InlineExecutorService.execute(InlineExecutorService.java:75) ~[tomcat-embed-core-9.0.17.jar:9.0.17]
at java.base/java.util.concurrent.AbstractExecutorService.submit(AbstractExecutorService.java:140) ~[na:na]
at org.apache.catalina.core.ContainerBase.startInternal(ContainerBase.java:902) ~[tomcat-embed-core-9.0.17.jar:9.0.17]
at org.apache.catalina.core.StandardEngine.startInternal(StandardEngine.java:262) ~[tomcat-embed-core-9.0.17.jar:9.0.17]
at org.apache.catalina.util.LifecycleBase.start(LifecycleBase.java:183) ~[tomcat-embed-core-9.0.17.jar:9.0.17]
at org.apache.catalina.core.StandardService.startInternal(StandardService.java:423) ~[tomcat-embed-core-9.0.17.jar:9.0.17]
at org.apache.catalina.util.LifecycleBase.start(LifecycleBase.java:183) ~[tomcat-embed-core-9.0.17.jar:9.0.17]
at org.apache.catalina.core.StandardServer.startInternal(StandardServer.java:928) ~[tomcat-embed-core-9.0.17.jar:9.0.17]
at org.apache.catalina.util.LifecycleBase.start(LifecycleBase.java:183) ~[tomcat-embed-core-9.0.17.jar:9.0.17]
at org.apache.catalina.startup.Tomcat.start(Tomcat.java:455) ~[tomcat-embed-core-9.0.17.jar:9.0.17]
at org.springframework.boot.web.embedded.tomcat.TomcatWebServer.initialize(TomcatWebServer.java:106) ~[spring-boot-2.1.4.RELEASE.jar:2.1.4.RELEASE]
at org.springframework.boot.web.embedded.tomcat.TomcatWebServer.(TomcatWebServer.java:86) ~[spring-boot-2.1.4.RELEASE.jar:2.1.4.RELEASE]
at org.springframework.boot.web.embedded.tomcat.TomcatServletWebServerFactory.getTomcatWebServer(TomcatServletWebServerFactory.java:427) ~[spring-boot-2.1.4.RELEASE.jar:2.1.4.RELEASE]
at org.springframework.boot.web.embedded.tomcat.TomcatServletWebServerFactory.getWebServer(TomcatServletWebServerFactory.java:180) ~[spring-boot-2.1.4.RELEASE.jar:2.1.4.RELEASE]
at org.springframework.boot.web.servlet.context.ServletWebServerApplicationContext.createWebServer(ServletWebServerApplicationContext.java:181) ~[spring-boot-2.1.4.RELEASE.jar:2.1.4.RELEASE]
at org.springframework.boot.web.servlet.context.ServletWebServerApplicationContext.onRefresh(ServletWebServerApplicationContext.java:154) ~[spring-boot-2.1.4.RELEASE.jar:2.1.4.RELEASE]
at org.springframework.context.support.AbstractApplicationContext.refresh(AbstractApplicationContext.java:543) ~[spring-context-5.1.6.RELEASE.jar:5.1.6.RELEASE]
at org.springframework.boot.web.servlet.context.ServletWebServerApplicationContext.refresh(ServletWebServerApplicationContext.java:142) ~[spring-boot-2.1.4.RELEASE.jar:2.1.4.RELEASE]
at org.springframework.boot.SpringApplication.refresh(SpringApplication.java:775) ~[spring-boot-2.1.4.RELEASE.jar:2.1.4.RELEASE]
at org.springframework.boot.SpringApplication.refreshContext(SpringApplication.java:397) ~[spring-boot-2.1.4.RELEASE.jar:2.1.4.RELEASE]
at org.springframework.boot.SpringApplication.run(SpringApplication.java:316) ~[spring-boot-2.1.4.RELEASE.jar:2.1.4.RELEASE]
at org.springframework.boot.SpringApplication.run(SpringApplication.java:1260) ~[spring-boot-2.1.4.RELEASE.jar:2.1.4.RELEASE]
at org.springframework.boot.SpringApplication.run(SpringApplication.java:1248) ~[spring-boot-2.1.4.RELEASE.jar:2.1.4.RELEASE]
at ...
Caused by: java.nio.file.InvalidPathException: Illegal char <:> at index 10: url('https:

.nis-flex-centered-content {
display: flex
at java.base/sun.nio.fs.WindowsPathParser.normalize(WindowsPathParser.java:182) ~[na:na]
at java.base/sun.nio.fs.WindowsPathParser.parse(WindowsPathParser.java:153) ~[na:na]
at java.base/sun.nio.fs.WindowsPathParser.parse(WindowsPathParser.java:77) ~[na:na]
at java.base/sun.nio.fs.WindowsPath.parse(WindowsPath.java:92) ~[na:na]
at java.base/sun.nio.fs.WindowsFileSystem.getPath(WindowsFileSystem.java:229) ~[na:na]
at java.base/java.nio.file.Path.resolve(Path.java:515) ~[na:na]
at com.vaadin.flow.server.frontend.TaskUpdateImports.resolve(TaskUpdateImports.java:251) ~[flow-server-2.0.2.jar:2.0.2]
at com.vaadin.flow.server.frontend.TaskUpdateImports.visitImportsRecursively(TaskUpdateImports.java:217) ~[flow-server-2.0.2.jar:2.0.2]
at com.vaadin.flow.server.frontend.TaskUpdateImports.handleImports(TaskUpdateImports.java:199) ~[flow-server-2.0.2.jar:2.0.2]
at com.vaadin.flow.server.frontend.TaskUpdateImports.visitImportsRecursively(TaskUpdateImports.java:225) ~[flow-server-2.0.2.jar:2.0.2]
at com.vaadin.flow.server.frontend.TaskUpdateImports.handleImports(TaskUpdateImports.java:199) ~[flow-server-2.0.2.jar:2.0.2]
at com.vaadin.flow.server.frontend.TaskUpdateImports.modulesToImports(TaskUpdateImports.java:163) ~[flow-server-2.0.2.jar:2.0.2]
at com.vaadin.flow.server.frontend.TaskUpdateImports.getMainJsContent(TaskUpdateImports.java:131) ~[flow-server-2.0.2.jar:2.0.2]
at com.vaadin.flow.server.frontend.TaskUpdateImports.execute(TaskUpdateImports.java:97) ~[flow-server-2.0.2.jar:2.0.2]
... 44 common frames omitted

The exception is thrown because com.vaadin.flow.server.frontend.ImportExtractor extracts the "@import" statement from CSS code inside the JS module:

const container = document.createElement('template');

container.innerHTML = `
    <dom-module id="gui-styles">
        <template>
            <style>
                @import url('https://fonts.googleapis.com/css?family=Montserrat:700');
...
            </style>
        </template>
    </dom-module>`;
document.head.appendChild(container.content);

- Vaadin / Flow version - vaadin version 14.0.0.rc4, flow-server-2.0.2.jar

[denis-anisimov]

Right, my bad.
We should not go into the content for extracting import statements.