Promote hidden to a first-class flag on PropertyDefinition

Persist `hidden` as an instance field on PropertyDefinition with a
public `hidden()` getter, so consumers can filter UI listings on it.

Drop the build-time mutex that forbade combining `.hidden()` with
`.onConfigScopes(...)` / `.onlyOnConfigScopes(...)`, and drop the
`if (hidden) global = false` coercion. `hidden` is now orthogonal to
`global` and `configScopes`, enabling per-project-settable properties
that are not exposed in the Settings UI.

Author: steve-marion-sonarsource

plugin-api/src/main/java/org/sonar/api/config/PropertyDefinition.java

@@ -136,6 +136,7 @@ private String getKey() {
   private final String category;
   private final List<ConfigScope> configScopes;
   private final boolean global;
+  private final boolean hidden;
   private final boolean multiValues;
   private final String deprecatedKey;
   private final List<PropertyFieldDefinition> fields;
@@ -153,6 +154,7 @@ private PropertyDefinition(Builder builder) {
     this.category = builder.category;
     this.subCategory = builder.subCategory;
     this.global = builder.global;
+    this.hidden = builder.hidden;
     this.type = builder.type;
     this.options = builder.options;
     this.multiValues = builder.multiValues;
@@ -344,6 +346,14 @@ public boolean global() {
     return global;
   }
 
+  /**
+   * Hidden properties are not discoverable, and typically don't appear in the UI.
+   * They can only be configured via the API.
+   */
+  public boolean hidden() {
+    return hidden;
+  }
+
   public boolean multiValues() {
     return multiValues;
   }
@@ -667,11 +677,7 @@ public PropertyDefinition build() {
       checkArgument(!isEmpty(key), "Key must be set");
       fixType(key, type);
       checkArgument(onConfigScopes.isEmpty() || onlyOnConfigScopes.isEmpty(), "Cannot use both forQualifiers and onlyForQualifiers");
-      checkArgument(!hidden || (onConfigScopes.isEmpty() && onlyOnConfigScopes.isEmpty()), "Cannot be hidden and defining qualifiers on which to display");
       checkArgument(!JSON.equals(type) || !multiValues, "Multivalues are not allowed to be defined for JSON-type property.");
-      if (hidden) {
-        global = false;
-      }
       if (!fields.isEmpty()) {
         type = PROPERTY_SET;
       }

plugin-api/src/test/java/org/sonar/api/config/PropertyDefinitionTest.java

@@ -108,7 +108,34 @@ public void should_create_hidden_property() {
     assertThat(def.key()).isEqualTo("hello");
     assertThat(def.qualifiers()).isEmpty();
     assertThat(def.configScopes()).isEmpty();
+    assertThat(def.global()).isTrue();
+    assertThat(def.hidden()).isTrue();
+  }
+
+  @Test
+  public void should_create_hidden_property_with_on_config_scopes() {
+    PropertyDefinition def = PropertyDefinition.builder("hello")
+      .name("Hello")
+      .hidden()
+      .onConfigScopes(ConfigScope.PROJECT)
+      .build();
+
+    assertThat(def.hidden()).isTrue();
+    assertThat(def.global()).isTrue();
+    assertThat(def.configScopes()).containsExactly(ConfigScope.PROJECT);
+  }
+
+  @Test
+  public void should_create_hidden_property_with_only_on_config_scopes() {
+    PropertyDefinition def = PropertyDefinition.builder("hello")
+      .name("Hello")
+      .hidden()
+      .onlyOnConfigScopes(ConfigScope.PROJECT)
+      .build();
+
+    assertThat(def.hidden()).isTrue();
     assertThat(def.global()).isFalse();
+    assertThat(def.configScopes()).containsExactly(ConfigScope.PROJECT);
   }
 
   @Test
@@ -125,6 +152,7 @@ public void should_create_property_with_default_values() {
     assertThat(def.description()).isEmpty();
     assertThat(def.type()).isEqualTo(PropertyType.STRING);
     assertThat(def.global()).isTrue();
+    assertThat(def.hidden()).isFalse();
     assertThat(def.qualifiers()).isEmpty();
     assertThat(def.configScopes()).isEmpty();
     assertThat(def.multiValues()).isFalse();
@@ -320,22 +348,6 @@ public void should_not_create_json_multivalue() {
       .hasMessage("Multivalues are not allowed to be defined for JSON-type property.");
   }
 
-  @Test
-  public void should_not_authorize_defining_on_qualifiers_and_hidden() {
-    Builder builder = PropertyDefinition.builder("foo").name("foo").onQualifiers(org.sonar.api.resources.Qualifiers.PROJECT).hidden();
-    assertThatThrownBy(builder::build)
-      .isInstanceOf(IllegalArgumentException.class)
-      .hasMessage("Cannot be hidden and defining qualifiers on which to display");
-  }
-
-  @Test
-  public void should_not_authorize_defining_ony_on_qualifiers_and_hidden() {
-    Builder builder = PropertyDefinition.builder("foo").name("foo").onlyOnQualifiers(org.sonar.api.resources.Qualifiers.PROJECT).hidden();
-    assertThatThrownBy(builder::build)
-      .isInstanceOf(IllegalArgumentException.class)
-      .hasMessage("Cannot be hidden and defining qualifiers on which to display");
-  }
-
   @Test
   public void should_not_authorize_defining_on_qualifiers_and_only_on_qualifiers() {
     Builder builder = PropertyDefinition.builder("foo").name("foo").onQualifiers(org.sonar.api.resources.Qualifiers.MODULE)