Add csv output format to validate command

You can now pass `--validation-format text|csv` to the validate
command to get CSV or text output. Text continues to be the default
when not specified.

smithy-cli/src/main/java/software/amazon/smithy/cli/commands/ModelBuilder.java

@@ -130,6 +130,13 @@ public Model build() {
                 : new ValidatorOptions();
         resolveMinSeverity(standardOptions, validatorOptions);
 
+        // Determine how to format the output, whether it's text (the default) or CSV.
+        // Only some commands (like validate) actually let you customize the output format, so assume a default.
+        ValidationEventFormatOptions formatOptions = arguments.hasReceiver(ValidationEventFormatOptions.class)
+                ? arguments.getReceiver(ValidationEventFormatOptions.class)
+                : new ValidationEventFormatOptions();
+        ValidationEventFormatOptions.ValidationFormat validationOutputFormat = formatOptions.format();
+
         ClassLoader classLoader = env.classLoader();
         ColorFormatter colors = env.colors();
         CliPrinter stderr = env.stderr();
@@ -180,13 +187,15 @@ public Model build() {
                 .titleLabel(titleLabel, titleLabelStyles)
                 .build();
 
+        validationOutputFormat.beginPrinting(validationPrinter);
         for (ValidationEvent event : sortedEvents) {
             // Only log events that are >= --severity. Note that setting --quiet inherently
             // configures events to need to be >= DANGER. Also filter using --show-validators and --hide-validators.
             if (validatorOptions.isVisible(event)) {
-                validationPrinter.println(formatter.format(event));
+                validationOutputFormat.print(validationPrinter, formatter, event);
             }
         }
+        validationOutputFormat.endPrinting(validationPrinter);
 
         env.flush();
         // Note: disabling validation will still show a summary of failures if the model can't be loaded.

smithy-cli/src/main/java/software/amazon/smithy/cli/commands/ValidateCommand.java

@@ -48,6 +48,7 @@ public int execute(Arguments arguments, Env env) {
         arguments.addReceiver(new DiscoveryOptions());
         arguments.addReceiver(new ValidatorOptions());
         arguments.addReceiver(new BuildOptions());
+        arguments.addReceiver(new ValidationEventFormatOptions());
 
         CommandAction action = HelpActionWrapper.fromCommand(
             this,

smithy-cli/src/main/java/software/amazon/smithy/cli/commands/ValidationEventFormatOptions.java

@@ -0,0 +1,98 @@
+/*
+ * Copyright Amazon.com, Inc. or its affiliates. All Rights Reserved.
+ * SPDX-License-Identifier: Apache-2.0
+ */
+
+package software.amazon.smithy.cli.commands;
+
+import java.util.function.Consumer;
+import software.amazon.smithy.cli.ArgumentReceiver;
+import software.amazon.smithy.cli.CliError;
+import software.amazon.smithy.cli.CliPrinter;
+import software.amazon.smithy.cli.HelpPrinter;
+import software.amazon.smithy.model.shapes.ShapeId;
+import software.amazon.smithy.model.validation.ValidationEvent;
+import software.amazon.smithy.model.validation.ValidationEventFormatter;
+
+final class ValidationEventFormatOptions implements ArgumentReceiver {
+
+    private static final String VALIDATION_FORMAT = "--validation-format";
+
+    enum ValidationFormat {
+        TEXT {
+            @Override
+            void print(CliPrinter printer, ValidationEventFormatter formatter, ValidationEvent event) {
+                printer.println(formatter.format(event));
+            }
+        },
+
+        CSV {
+            @Override
+            void beginPrinting(CliPrinter printer) {
+                printer.println("severity,id,shape,file,message,hint,suppressionReason");
+            }
+
+            @Override
+            void print(CliPrinter printer, ValidationEventFormatter formatter, ValidationEvent event) {
+                printer.println(
+                        String.format("\"%s\",\"%s\",\"%s\",\"%s\",\"%s\",\"%s\",\"%s\"",
+                                      event.getSeverity().toString(),
+                                      formatCsv(event.getId()),
+                                      event.getShapeId().map(ShapeId::toString).orElse(""),
+                                      formatCsv(
+                                              event.getSourceLocation().getFilename()
+                                              + ':' + event.getSourceLocation().getLine()
+                                              + ':' + event.getSourceLocation().getColumn()),
+                                      formatCsv(event.getMessage()),
+                                      formatCsv(event.getHint().orElse("")),
+                                      formatCsv(event.getSuppressionReason().orElse(""))));
+            }
+        };
+
+        void beginPrinting(CliPrinter printer) {}
+
+        abstract void print(CliPrinter printer, ValidationEventFormatter formatter, ValidationEvent event);
+
+        void endPrinting(CliPrinter printer) {}
+
+        private static String formatCsv(String value) {
+            // Replace DQUOTE with DQUOTEDQUOTE and escape newlines.
+            return value.replace("\"", "\"\"").replace("\n", "\\n");
+        }
+    }
+
+    private ValidationFormat format = ValidationFormat.TEXT;
+
+    @Override
+    public void registerHelp(HelpPrinter printer) {
+        printer.param(VALIDATION_FORMAT, null, "text|csv",
+                      "Specifies the format to write validation events (text or csv). Defaults to text.");
+    }
+
+    @Override
+    public Consumer<String> testParameter(String name) {
+        if (name.equals("--validation-format")) {
+            return s -> {
+                switch (s) {
+                    case "csv":
+                        format(ValidationFormat.CSV);
+                        break;
+                    case "text":
+                        format(ValidationFormat.TEXT);
+                        break;
+                    default:
+                        throw new CliError("Unexpected " + VALIDATION_FORMAT + ": `" + s + "`");
+                }
+            };
+        }
+        return null;
+    }
+
+    void format(ValidationFormat format) {
+        this.format = format;
+    }
+
+    ValidationFormat format() {
+        return format;
+    }
+}

smithy-cli/src/test/java/software/amazon/smithy/cli/commands/ValidateCommandTest.java

@@ -18,7 +18,6 @@
 import static org.hamcrest.MatcherAssert.assertThat;
 import static org.hamcrest.Matchers.containsString;
 import static org.hamcrest.Matchers.equalTo;
-import static org.hamcrest.Matchers.is;
 import static org.hamcrest.Matchers.not;
 
 import java.net.URISyntaxException;
@@ -216,4 +215,38 @@ public void canHideEventsById() throws Exception {
         assertThat(result.stdout(), not(containsString("EmitDangers")));
         assertThat(result.stdout(), containsString("HttpLabelTrait"));
     }
+
+    @Test
+    public void canOutputCsv() throws Exception {
+        Path validationEventsModel = Paths.get(getClass().getResource("validation-events.smithy").toURI());
+        CliUtils.Result result = CliUtils.runSmithy("validate", "--validation-format", "csv",
+                                                    validationEventsModel.toString());
+
+        assertThat(result.code(), not(0));
+        assertThat(result.stdout(), containsString("suppressionReason"));
+        assertThat(result.stdout(), containsString("EmitWarnings"));
+        assertThat(result.stdout(), containsString("EmitDangers"));
+        assertThat(result.stdout(), containsString("HttpLabelTrait"));
+    }
+
+    @Test
+    public void canOutputText() throws Exception {
+        Path validationEventsModel = Paths.get(getClass().getResource("validation-events.smithy").toURI());
+        CliUtils.Result result = CliUtils.runSmithy("validate", "--validation-format", "text",
+                                                    validationEventsModel.toString());
+
+        assertThat(result.code(), not(0));
+        assertThat(result.stdout(), not(containsString("suppressionReason")));
+        assertThat(result.stdout(), containsString("EmitWarnings"));
+        assertThat(result.stdout(), containsString("EmitDangers"));
+        assertThat(result.stdout(), containsString("HttpLabelTrait"));
+    }
+
+    @Test
+    public void outputFormatMustBeValid() {
+        CliUtils.Result result = CliUtils.runSmithy("validate", "--validation-format", "HELLO");
+
+        assertThat(result.code(), not(0));
+        assertThat(result.stderr(), containsString("Unexpected --validation-format: `HELLO`"));
+    }
 }