Fix broken npx goal when using a proxy

[123Haynes]

Summary

This PR
fixes #1030
fixes #1121
fixes #1105
in the current version of the plugin the npx goal is broken when using a proxy.

As you can read in the npm documentation npx does not support the syntax that was used by the plugin before:
https://docs.npmjs.com/cli/v8/commands/npm-exec#npx-vs-npm-exec

When run via the npx binary, all flags and options must be set prior to any positional arguments.

syntax before:
npx @sompackage arg1 arg2 -- --proxy=someproxy --https-proxy=someproxy --registry=someregistry

syntax after:
npx --proxy=someproxy --https-proxy=someproxy --registry=someregistry @somepackage arg1 arg2

npm supports both syntax so no harm done in switching it.

Tests and Documentation

I've changed the 3 existing tests to check for the new syntax.
Please let me know if you need other changes. I'll try to get to it asap 😃

[123Haynes]

This PR should also fix #1105 since yarn accepts the same syntax.

[123Haynes]

@eirslett can you take a look when you have time? 😃

[mojavelinux]

I agree that the extra npm arguments are being added on the wrong side of the command that npx is running. The Javadoc for the NpxRunner states npm arguments, that need to be split from the npx arguments by '--'. However, the docs for the npx command show that this separator is meant to come before the command and its arguments that npx is running:

npx --package=<pkg>[@<version>] -- <cmd> [args...]

As this issue states, the reverse is happening. --registry and related options are being added at the end. What ends up happening is that the command sees these extra options and doesn't know what to do with them and may fail.

Here's a reproducible case to demonstrate

<?xml version="1.0" encoding="UTF-8"?>
<project xmlns="https://maven.apache.org/POM/4.0.0" xmlns:xsi="https://www.w3.org/2001/XMLSchema-instance" xsi:schemaLocation="https://maven.apache.org/POM/4.0.0 https://maven.apache.org/xsd/maven-4.0.0.xsd">
  <modelVersion>4.0.0</modelVersion>
  <groupId>org.example</groupId>
  <artifactId>frontend-maven-plugin-example</artifactId>
  <version>1.0.0-SNAPSHOT</version>
  <packaging>pom</packaging>
  <build>
    <plugins>
      <plugin>
        <groupId>com.github.eirslett</groupId>
        <artifactId>frontend-maven-plugin</artifactId>
        <version>1.15.0</version>
        <configuration>
          <environmentVariables>
            <npm_config_cache>${project.build.directory}/_npx</npm_config_cache>
          </environmentVariables>
          <installDirectory>${project.build.directory}</installDirectory>
          <nodeVersion>v20.12.2</nodeVersion>
        </configuration>
        <executions>
          <execution>
            <id>install-node</id>
            <goals>
              <goal>install-node-and-npm</goal>
            </goals>
            <phase>initialize</phase>
          </execution>
          <execution>
            <id>run-npx</id>
            <goals>
              <goal>npx</goal>
            </goals>
            <phase>process-resources</phase>
            <configuration>
              <arguments>--yes --package js-yaml js-yaml test.yml</arguments>
            </configuration>
          </execution>
        </executions>
      </plugin>
    </plugins>
  </build>
</project>

First, create the test.yml file to load.

test.yml

key: value

If you run the following command, it will work:

mvn clean process-resources

However, if you pass an npm registry URL:

mvn clean process-resources -DnpmRegistryURL=https://registry.yarnpkg.com

here's what it will run:

npx --yes --package js-yaml js-yaml test.yml -- --registry=https://registry.yarnpkg.com

Notice that the --registry option comes after the command that npx is running. As a result, the js-yaml command will report the following error message:

js-yaml: error: unrecognized arguments: --registry=https://registry.yarnpkg.com

There are many commands that don't recognize these extra arguments that are supposed to be passed to npm itself. Here's how the command should look to solve this problem:

npx --registry=https://registry.yarnpkg.com --yes --package js-yaml js-yaml test.yml

There's also no need for the -- separator since npx handles that automatically based on when it sees the first positional argument.