[MNG-6401] Support interpolation of the proxy port in settings.xml (#1194)

Co-authored-by: Hervé Boutemy <hboutemy@apache.org>
Co-authored-by: Michael Osipov <michaelo@apache.org>

api/maven-api-settings/src/main/mdo/settings.mdo

@@ -459,17 +459,17 @@
         The <code>&lt;proxy&gt;</code> element contains informations required to a proxy settings.
         ]]></description>
       <fields>
-        <field>
-          <name>active</name>
+        <field xml.tagName="active">
+          <name>activeString</name>
           <version>1.0.0+</version>
           <required>false</required>
           <defaultValue>true</defaultValue>
           <description>
-            <![CDATA[
-            Whether this proxy configuration is the active one.
-            ]]>
+            Whether this proxy configuration is the active one. Note: While the type of this field
+            is {@code String} for technical reasons, the semantic type is actually {@code boolean}.
+            @see #isActive()
           </description>
-          <type>boolean</type>
+          <type>String</type>
         </field>
         <field>
           <name>protocol</name>
@@ -502,15 +502,15 @@
           </description>
           <type>String</type>
         </field>
-        <field>
-          <name>port</name>
+        <field xml.tagName="port">
+          <name>portString</name>
           <version>1.0.0+</version>
           <description>
-            <![CDATA[
-            The proxy port.
-            ]]>
+            The proxy port. Note: While the type of this field is {@code String} for technical
+            reasons, the semantic type is actually {@code int}.
+            @see #getPort()
           </description>
-          <type>int</type>
+          <type>String</type>
           <defaultValue>8080</defaultValue>
         </field>
         <field>
@@ -535,6 +535,57 @@
           <type>String</type>
         </field>
       </fields>
+      <codeSegments>
+        <codeSegment>
+          <version>1.0.0/1.3.0</version>
+          <code>
+    public boolean isActive() {
+        return (getActiveString() != null) ? Boolean.parseBoolean(getActiveString()) : true;
+    }
+
+    public void setActive(boolean active) {
+        setActiveString(String.valueOf(active));
+    }
+
+    public int getPort() {
+        return (getPortString() != null) ? Integer.parseInt(getPortString()) : 8080;
+    }
+
+    public void setPort(int port) {
+        setPortString(String.valueOf(port));
+    }
+          </code>
+        </codeSegment>
+        <codeSegment>
+          <version>2.0.0+</version>
+          <code>
+    /**
+     * Indicates if this proxy is active.
+     * To allow interpolation of this field, this method lazily parses
+     * the {@link #getActiveString()} value as a boolean and defaults to {@code true}
+     * if not set.
+     *
+     * @return a boolean indicating if this proxy is active
+     */
+    public boolean isActive() {
+        return (getActiveString() != null) ? Boolean.parseBoolean(getActiveString()) : true;
+    }
+
+    /**
+     * Returns the port to use for this proxy.
+     * To allow interpolation of this field, this method lazily parses
+     * the {@link #getPortString()} value as an integer and defaults to {@code 8080}
+     * if not set.
+     *
+     * @return an integer indicating the port to use for this proxy
+     */
+    public int getPort() {
+        return (getPortString() != null) ? Integer.parseInt(getPortString()) : 8080;
+    }
+
+          </code>
+        </codeSegment>
+      </codeSegments>
     </class>
     <class>
       <name>Server</name>

maven-settings-builder/src/main/java/org/apache/maven/settings/building/DefaultSettingsBuilder.java

@@ -128,8 +128,6 @@ public class DefaultSettingsBuilder implements SettingsBuilder {
 
         problems.setSource("");
 
-        userSettings = interpolate(userSettings, request, problems);
-
         // for the special case of a drive-relative Windows path, make sure it's absolute to save plugins from trouble
         String localRepository = userSettings.getLocalRepository();
         if (localRepository != null && localRepository.length() > 0) {
@@ -212,6 +210,8 @@ public class DefaultSettingsBuilder implements SettingsBuilder {
             return new Settings();
         }
 
+        settings = interpolate(settings, request, problems);
+
         settingsValidator.validate(settings, isProjectSettings, problems);
 
         if (isProjectSettings) {

maven-settings-builder/src/main/java/org/apache/maven/settings/validation/DefaultSettingsValidator.java

@@ -195,6 +195,17 @@ public class DefaultSettingsValidator implements SettingsValidator {
                             "must be unique but found duplicate proxy with id " + proxy.getId());
                 }
                 validateStringNotEmpty(problems, "proxies.proxy.host", proxy.getHost(), proxy.getId());
+
+                try {
+                    Integer.parseInt(proxy.getPortString());
+                } catch (NumberFormatException e) {
+                    addViolation(
+                            problems,
+                            Severity.ERROR,
+                            "proxies.proxy[" + proxy.getId() + "].port",
+                            null,
+                            "must be a valid integer but found '" + proxy.getPortString() + "'");
+                }
             }
         }
     }