[OPENJDK-1549] Mvn project to test for MAVEN_ARGS

Simple test Maven project for which the validate phase will fail
if MAVEN_ARGS is defined in the environment and pass otherwise.

Signed-off-by: Jonathan Dowland <[email protected]>

Author: jmtd

tests/OPENJDK-1549/README.md

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+# Test for OPENJDK-1549
+
+<https://issues.redhat.com/browse/OPENJDK-1549>
+
+This is a minimal Maven project for which the `validate` target will fail
+if the environment variable `MAVEN_ARGS` is defined.
+
+This is achieved using the Enforcer plugin. We could not use the
+`requireEnvironmentVariable` built-in rule as it can only fail if a variable
+is undefined, rather than if it is. Instead we use `evaluateBeanshell` and
+a very short Beanshell expression.
+
+Maven expands strings of the form `${env.foo}` within the POM only if the
+variable is defined. That is, when `MAVEN_ARGS` is not defined in the
+environment, the string `${env.MAVEN_ARGS}` is passed through unaltered.
+If the variable is defined (including defined but empty), Maven will expand
+it. Some string concatenation trickery is needed to match against the
+un-expanded form.

tests/OPENJDK-1549/pom.xml

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+<?xml version="1.0" encoding="UTF-8"?>
+<project>
+  <modelVersion>4.0.0</modelVersion>
+  <groupId>org.acme</groupId>
+  <artifactId>getting-started</artifactId>
+  <version>1.0.0-SNAPSHOT</version>
+  <build>
+    <plugins>
+      <plugin>
+        <groupId>org.apache.maven.plugins</groupId>
+        <artifactId>maven-enforcer-plugin</artifactId>
+        <version>3.3.0</version>
+        <executions>
+
+          <!-- ensure the environment variable MAVEN_ARGS is unset -->
+          <execution>
+            <id>enforce-beanshell</id>
+            <goals>
+              <goal>enforce</goal>
+            </goals>
+            <configuration>
+              <rules>
+                <evaluateBeanshell>
+                  <condition>"${env.MAVEN_ARGS}".equals("${env."+"MAVEN_ARGS}")</condition>
+                </evaluateBeanshell>
+              </rules>
+              <fail>true</fail>
+            </configuration>
+          </execution>
+
+        </executions>
+      </plugin>
+    </plugins>
+  </build>
+</project>