feat: CLI command to run formatting (#824)

Closes #702

### Summary of Changes

Add a new `format` command to format Safe-DS files.

packages/safe-ds-cli/src/cli/format.ts

@@ -0,0 +1,35 @@
+import { createSafeDsServicesWithBuiltins } from '@safe-ds/lang';
+import { NodeFileSystem } from 'langium/node';
+import { extractDocuments } from '../helpers/documents.js';
+import { exitIfDocumentHasSyntaxErrors } from '../helpers/diagnostics.js';
+import { TextDocument } from 'vscode-languageserver-textdocument';
+import { writeFile } from 'node:fs/promises';
+import chalk from 'chalk';
+
+export const format = async (fsPaths: string[]): Promise<void> => {
+    const services = (await createSafeDsServicesWithBuiltins(NodeFileSystem)).SafeDs;
+    const documents = await extractDocuments(services, fsPaths);
+
+    // Exit if any document has syntax errors before formatting code
+    for (const document of documents) {
+        exitIfDocumentHasSyntaxErrors(document);
+    }
+
+    // Format code
+    for (const document of documents) {
+        const edits = await services.lsp.Formatter!.formatDocument(document, {
+            textDocument: {
+                uri: document.uri.toString(),
+            },
+            options: {
+                tabSize: 4,
+                insertSpaces: true,
+            },
+        });
+
+        const editedDocument = TextDocument.applyEdits(document.textDocument, edits);
+        await writeFile(document.uri.fsPath, editedDocument);
+    }
+
+    console.log(chalk.green(`Safe-DS code formatted successfully.`));
+};

packages/safe-ds-cli/src/cli/main.ts

@@ -3,6 +3,7 @@ import { createRequire } from 'node:module';
 import { fileURLToPath } from 'node:url';
 import { generate } from './generate.js';
 import { check } from './check.js';
+import { format } from './format.js';
 
 const program = new Command();
 
@@ -19,6 +20,13 @@ program
     .description('check Safe-DS code')
     .action(check);
 
+// Format command
+program
+    .command('format')
+    .argument('<paths...>', `list of files or directories to format`)
+    .description('format Safe-DS code')
+    .action(format);
+
 // Generate command
 program
     .command('generate')

packages/safe-ds-cli/src/helpers/diagnostics.ts

@@ -99,6 +99,24 @@ export const exitIfDocumentHasErrors = function (document: LangiumDocument): voi
     }
 };
 
+/**
+ * Exits the process if the given document has syntax errors.
+ */
+export const exitIfDocumentHasSyntaxErrors = function (document: LangiumDocument): void {
+    const errors = getSyntaxErrors(document);
+    if (errors.length > 0) {
+        console.error(chalk.red(`The file '${uriToRelativePath(document.uri)}' has syntax errors:`));
+        for (const error of errors) {
+            console.error(diagnosticToString(document.uri, error));
+        }
+        process.exit(ExitCode.FileHasErrors);
+    }
+};
+
 const getErrors = (document: LangiumDocument): Diagnostic[] => {
     return getDiagnostics(document).filter((it) => it.severity === DiagnosticSeverity.Error);
 };
+
+const getSyntaxErrors = (document: LangiumDocument): Diagnostic[] => {
+    return getErrors(document).filter((d) => d.data?.code === 'lexing-error' || d.data?.code === 'parsing-error');
+};

packages/safe-ds-cli/tests/cli/main.test.ts

@@ -93,6 +93,52 @@ describe('safe-ds', () => {
         });
     });
 
+    describe('format', () => {
+        const testResourcesRoot = new URL('../resources/format/', import.meta.url);
+        const spawnFormatProcess = (additionalArguments: string[], paths: string[]) => {
+            const fsPaths = paths.map((p) => fileURLToPath(new URL(p, testResourcesRoot)));
+            return spawnSync('node', ['./bin/cli', 'format', ...additionalArguments, ...fsPaths], {
+                cwd: projectRoot,
+            });
+        };
+
+        it('should show an error if no paths are passed', () => {
+            const process = spawnFormatProcess([], []);
+            expect(process.stderr.toString()).toContain("error: missing required argument 'paths'");
+            expect(process.status).not.toBe(ExitCode.Success);
+        });
+
+        it('should show usage on stdout if -h flag is passed', () => {
+            const process = spawnFormatProcess(['-h'], []);
+            expect(process.stdout.toString()).toContain('Usage: cli format');
+            expect(process.status).toBe(ExitCode.Success);
+        });
+
+        it('should show errors in wrong files', () => {
+            const process = spawnFormatProcess([], ['.']);
+            expect(process.stderr.toString()).toContain('has syntax errors');
+            expect(process.status).toBe(ExitCode.FileHasErrors);
+        });
+
+        it('should show not show errors in correct files', () => {
+            const process = spawnFormatProcess([], ['correct.sdstest']);
+            expect(process.stdout.toString()).toContain('Safe-DS code formatted successfully.');
+            expect(process.status).toBe(ExitCode.Success);
+        });
+
+        it('should show an error if the file does not exist', () => {
+            const process = spawnFormatProcess([], ['missing.sdstest']);
+            expect(process.stderr.toString()).toMatch(/Path .* does not exist\./u);
+            expect(process.status).toBe(ExitCode.MissingPath);
+        });
+
+        it('should show an error if a file has the wrong extension', () => {
+            const process = spawnFormatProcess([], ['not safe-ds.txt']);
+            expect(process.stderr.toString()).toContain('does not have a Safe-DS extension');
+            expect(process.status).toBe(ExitCode.FileWithoutSafeDsExtension);
+        });
+    });
+
     describe('generate', () => {
         const testResourcesRoot = new URL('../resources/generate/', import.meta.url);
         const spawnGenerateProcess = (additionalArguments: string[], paths: string[]) => {

packages/safe-ds-cli/tests/resources/format/contains syntax errors.sdstest

@@ -0,0 +1,3 @@
+package test
+
+segment mySegment()

packages/safe-ds-cli/tests/resources/format/correct.sdstest

@@ -0,0 +1,3 @@
+package test
+
+pipeline myPipeline {}

packages/safe-ds-cli/tests/resources/format/not safe-ds.txt

@@ -0,0 +1,3 @@
+package test
+
+segment mySegment() {}