Add delete and add methods for parsers in global configuration

doc/Documentation.md

@@ -228,7 +228,9 @@ text into an issue instance. Here is an example of such a Groovy based parser:
 #### Creating a Groovy parser programmatically
 
 The Groovy based parser can also be created using a Groovy script from within a pipeline, a Jenkins startup script or 
-the script console, see the following example:
+the script console.
+
+See the following example:
 
 ```groovy
 def config = io.jenkins.plugins.analysis.warnings.groovy.ParserConfiguration.getInstance()
@@ -241,7 +243,7 @@ if(!config.contains('pep8-groovy')){
         'return builder.setFileName(matcher.group(1)).setCategory(matcher.group(4)).setMessage(matcher.group(5)).buildOptional()', 
         "optparse.py:69:11: E401 multiple imports on one line"
     )
-    config.setParsers(config.getParsers().plus(newParser))
+    config.addParser(newParser)
 }
 ```
 

plugin/src/main/java/io/jenkins/plugins/analysis/warnings/groovy/ParserConfiguration.java

@@ -87,6 +87,39 @@
         save();
     }
 
+    /**
+     * Removes a GroovyParser from the list by Id.
+     *
+     * @param parserId
+     *         the ID of the Groovy parser to be deleted
+     */
+    public void deleteParser(final String parserId) {
+        if (contains(parserId)) {
+            GroovyParser parser = getParser(parserId);
+            this.parsers.remove(parser);
+        }
+        else {
+            throw new NoSuchElementException(String.format("No Groovy parser with ID '%s' found.", parserId));
+        }
+        save();
+    }
+
+    /**
+     * Adds a GroovyParser to the list without removing other parsers.
+     *
+     * @param parser
+     *         the new Groovy parser to be added
+     */
+    public void addParser(final GroovyParser parser) {
+        String parserId = parser.getId();
+        if (contains(parserId)) {
+            throw new IllegalArgumentException(String.format("ID '%s' already exists.", parserId));
+        }
+        this.parsers.add(parser);
+
+        save();
+    }
+
     /**
      * Says if the admin has permitted groovy parsers to scan a build's console log.
      *

plugin/src/test/java/io/jenkins/plugins/analysis/warnings/groovy/ParserConfigurationTest.java

@@ -27,7 +27,7 @@ void shouldHaveNoParsersWhenCreated() {
     }
 
     @Test
-    void shouldSaveConfigurationIfParsersAreAdded() {
+    void shouldSaveConfigurationIfParsersAreSet() {
         GlobalConfigurationFacade facade = mock(GlobalConfigurationFacade.class);
 
         ParserConfiguration configuration = new ParserConfiguration(facade);
@@ -68,4 +68,45 @@ void shouldWarnUserIfConsoleLogScanningPermittedIsSet() {
         final FormValidation actualTrue = configuration.doCheckConsoleLogScanningPermitted(true);
         assertThat(actualTrue.kind).isEqualTo(FormValidation.Kind.WARNING);
     }
+
+    @Test
+    void shouldSaveConfigurationIfParserIsAdded() {
+        GlobalConfigurationFacade facade = mock(GlobalConfigurationFacade.class);
+        GroovyParser additionalParser = new GroovyParser("1", "", "", "", "");
+
+        ParserConfiguration configuration = new ParserConfiguration(facade);
+        configuration.addParser(additionalParser);
+
+        verify(facade).save();
+        assertThat(configuration.getParsers()).containsExactly(additionalParser);
+    }
+
+    @Test
+    void shouldThrowIfParserExists() {
+        GlobalConfigurationFacade facade = mock(GlobalConfigurationFacade.class);
+        GroovyParser testParser = new GroovyParser("1", "", "", "", "");
+
+        ParserConfiguration configuration = new ParserConfiguration(facade);
+        configuration.addParser(testParser);
+        verify(facade).save();
+
+        assertThatIllegalArgumentException().isThrownBy(() -> configuration.addParser(testParser)).withMessageContaining(testParser.getId());
+    }
+
+    @Test
+    void deleteShouldRemoveOnlySpecifiedParser() {
+        GlobalConfigurationFacade facade = mock(GlobalConfigurationFacade.class);
+        GroovyParser firstTestParser = new GroovyParser("1", "", "", "", "");
+        GroovyParser secondTestParser = new GroovyParser("2", "", "", "", "");
+
+        ParserConfiguration configuration = new ParserConfiguration(facade);
+        configuration.addParser(firstTestParser);
+        configuration.addParser(secondTestParser);
+
+        assertThat(configuration.getParsers()).containsExactly(firstTestParser, secondTestParser);
+
+        configuration.deleteParser(firstTestParser.getId());
+        assertThat(configuration.getParsers()).containsExactly(secondTestParser);
+
+    }
 }

plugin/src/test/java/io/jenkins/plugins/analysis/warnings/steps/StepsITest.java

@@ -815,6 +815,33 @@ void shouldShowWarningsOfGroovyParserWhenScanningConsoleLogWhenThatIsPermitted()
         testGroovyPep8JobIsSuccessful(job, id);
     }
 
+    /**
+     * Registers a new {@link GroovyParser} (a Pep8 parser) in Jenkins global configuration and runs this parser on the
+     * console that's showing an error log with 8 issues.
+     *
+     * @throws IOException
+     *         if the test fails unexpectedly
+     */
+    @Test
+    void shouldShowWarningsOfGroovyParserWhenScanningConsoleLogWhenThatIsPermittedAndUsingAddParser() throws IOException {
+        WorkflowJob job = createPipeline();
+        ArrayList<String> stages = new ArrayList<>();
+        catFileContentsByAddingEchosSteps(stages, "pep8Test.txt");
+        stages.add("def groovy = scanForIssues "
+                + "tool: groovyScript(parserId: 'another-groovy-pep8', pattern:'', reportEncoding:'UTF-8')");
+        stages.add("publishIssues issues:[groovy]");
+        job.setDefinition(asStage(stages.toArray(new String[0])));
+
+        ParserConfiguration configuration = ParserConfiguration.getInstance();
+        configuration.setConsoleLogScanningPermitted(true);
+        String id = "another-groovy-pep8";
+
+        configuration.addParser(new GroovyParser(id, "Another Groovy Pep8",
+                        "(.*):(\\d+):(\\d+): (\\D\\d*) (.*)",
+                        toString("groovy/pep8.groovy"), ""));
+        testGroovyPep8JobIsSuccessful(job, id);
+    }
+
     /**
      * Registers a new {@link GroovyParser} (a Pep8 parser) in Jenkins global configuration and runs this parser on the
      * console that's showing an error log with 8 issues ... but when we're configured not to allow groovy parsers to