feat: Validation for conditionally required/forbidden fare_rules.txt file.

RULES.md

@@ -41,6 +41,7 @@ Each Notice is associated with a severity: `INFO`, `WARNING`, `ERROR`.
 | [`empty_column_name`](#empty_column_name)                                                                         | A column name is empty.                                                                                                                                |
 | [`empty_file`](#empty_file)                                                                                       | A CSV file is empty.                                                                                                                                   |
 | [`equal_shape_distance_diff_coordinates`](#equal_shape_distance_diff_coordinates)                                 | Two consecutive points have equal `shape_dist_traveled` and different lat/lon coordinates in `shapes.txt`.                                             |
+| [`forbidden_file`](#forbidden_file)                                                                               | A conditionally forbidden file is present in the feed.                                                                                                 |
 | [`foreign_key_violation`](#foreign_key_violation)                                                                 | Wrong foreign key.                                                                                                                                     |
 | [`inconsistent_agency_timezone`](#inconsistent_agency_timezone)                                                   | Inconsistent Timezone among agencies.                                                                                                                  |
 | [`invalid_color`](#invalid_color)                                                                                 | A field contains an invalid color value.                                                                                                               |
@@ -184,6 +185,26 @@ Trips with the same block id have overlapping stop times.
 
 </details>
 
+<a name="ForbiddenFileNotice"/>
+
+### forbidden_file
+
+A conditionally forbidden file is present in the feed.
+
+#### References
+* [GTFS terms definition](https://gtfs.org/reference/static/#term-definitions)
+<details>
+
+#### Notice fields description
+| Field name   	| Description                    	| Type   	|
+|--------------	|--------------------------------	|--------	|
+| `filename`   	| The name of the forbidden file.   	| String 	|
+
+#### Affected files
+[All GTFS files supported by the specification.](http://gtfs.org/reference/static#dataset-files)
+
+</details>
+
 <a name="CsvParsingFailedNotice"/>
 
 ### csv_parsing_failed

core/src/main/java/org/mobilitydata/gtfsvalidator/notice/ForbiddenFileNotice.java

@@ -0,0 +1,31 @@
+/*
+ * Copyright 2020 Google LLC
+ *
+ * Licensed under the Apache License, Version 2.0 (the "License");
+ * you may not use this file except in compliance with the License.
+ * You may obtain a copy of the License at
+ *
+ * http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ */
+
+package org.mobilitydata.gtfsvalidator.notice;
+
+/**
+ * A conditionally forbidden file is present in the feed.
+ *
+ * <p>Severity: {@code SeverityLevel.ERROR}
+ */
+public class ForbiddenFileNotice extends ValidationNotice {
+  private final String filename;
+
+  public ForbiddenFileNotice(String filename) {
+    super(SeverityLevel.ERROR);
+    this.filename = filename;
+  }
+}

main/src/main/java/org/mobilitydata/gtfsvalidator/validator/FaresV1FileValidator.java

@@ -0,0 +1,32 @@
+package org.mobilitydata.gtfsvalidator.validator;
+
+import javax.inject.Inject;
+import org.mobilitydata.gtfsvalidator.notice.ForbiddenFileNotice;
+import org.mobilitydata.gtfsvalidator.notice.MissingRequiredFileNotice;
+import org.mobilitydata.gtfsvalidator.notice.NoticeContainer;
+import org.mobilitydata.gtfsvalidator.table.GtfsFareAttributeTableContainer;
+import org.mobilitydata.gtfsvalidator.table.GtfsFareRuleTableContainer;
+
+public class FaresV1FileValidator extends FileValidator {
+
+  private final GtfsFareAttributeTableContainer fareAttributeTable;
+  private final GtfsFareRuleTableContainer fareRuleTable;
+
+  @Inject
+  public FaresV1FileValidator(
+      GtfsFareAttributeTableContainer fareAttributeTable,
+      GtfsFareRuleTableContainer fareRuleTable) {
+    this.fareAttributeTable = fareAttributeTable;
+    this.fareRuleTable = fareRuleTable;
+  }
+
+  @Override
+  public void validate(NoticeContainer noticeContainer) {
+    if (!fareAttributeTable.isMissingFile() && fareRuleTable.isMissingFile()) {
+      noticeContainer.addValidationNotice(
+          new MissingRequiredFileNotice(fareRuleTable.gtfsFilename()));
+    } else if (fareAttributeTable.isMissingFile() && !fareRuleTable.isMissingFile()) {
+      noticeContainer.addValidationNotice(new ForbiddenFileNotice(fareRuleTable.gtfsFilename()));
+    }
+  }
+}

main/src/test/java/org/mobilitydata/gtfsvalidator/validator/FaresV1FileValidatorTest.java

@@ -0,0 +1,65 @@
+package org.mobilitydata.gtfsvalidator.validator;
+
+import static com.google.common.truth.Truth.assertThat;
+
+import junit.framework.TestCase;
+import org.junit.Test;
+import org.mobilitydata.gtfsvalidator.notice.ForbiddenFileNotice;
+import org.mobilitydata.gtfsvalidator.notice.MissingRequiredFileNotice;
+import org.mobilitydata.gtfsvalidator.notice.NoticeContainer;
+import org.mobilitydata.gtfsvalidator.table.GtfsFareAttributeTableContainer;
+import org.mobilitydata.gtfsvalidator.table.GtfsFareRuleTableContainer;
+import org.mobilitydata.gtfsvalidator.table.GtfsTableContainer.TableStatus;
+
+public class FaresV1FileValidatorTest extends TestCase {
+
+  private NoticeContainer noticeContainer = new NoticeContainer();
+
+  @Test
+  public void testFareAttributesPresentAndFareRulesPresent() {
+    new FaresV1FileValidator(
+            new GtfsFareAttributeTableContainer(TableStatus.PARSABLE_HEADERS_AND_ROWS),
+            new GtfsFareRuleTableContainer(TableStatus.PARSABLE_HEADERS_AND_ROWS))
+        .validate(noticeContainer);
+    assertThat(noticeContainer.getValidationNotices()).isEmpty();
+  }
+
+  @Test
+  public void testFareAttributesPresentAndFareRulesPresentByEmpty() {
+    // We still consider an empty file to be "present".
+    new FaresV1FileValidator(
+            new GtfsFareAttributeTableContainer(TableStatus.EMPTY_FILE),
+            new GtfsFareRuleTableContainer(TableStatus.EMPTY_FILE))
+        .validate(noticeContainer);
+    assertThat(noticeContainer.getValidationNotices()).isEmpty();
+  }
+
+  @Test
+  public void testFareAttributesMissingAndFareRulesMissing() {
+    new FaresV1FileValidator(
+            new GtfsFareAttributeTableContainer(TableStatus.MISSING_FILE),
+            new GtfsFareRuleTableContainer(TableStatus.MISSING_FILE))
+        .validate(noticeContainer);
+    assertThat(noticeContainer.getValidationNotices()).isEmpty();
+  }
+
+  @Test
+  public void testFareAttributesPresentButFareRulesMissing() {
+    new FaresV1FileValidator(
+            new GtfsFareAttributeTableContainer(TableStatus.PARSABLE_HEADERS_AND_ROWS),
+            new GtfsFareRuleTableContainer(TableStatus.MISSING_FILE))
+        .validate(noticeContainer);
+    assertThat(noticeContainer.getValidationNotices())
+        .containsExactly(new MissingRequiredFileNotice("fare_rules.txt"));
+  }
+
+  @Test
+  public void testFareAttributesMissingButFareRulesPresent() {
+    new FaresV1FileValidator(
+            new GtfsFareAttributeTableContainer(TableStatus.MISSING_FILE),
+            new GtfsFareRuleTableContainer(TableStatus.PARSABLE_HEADERS_AND_ROWS))
+        .validate(noticeContainer);
+    assertThat(noticeContainer.getValidationNotices())
+        .containsExactly(new ForbiddenFileNotice("fare_rules.txt"));
+  }
+}