feat(variables): Add check for padwalker

It can be difficult for newcommers to know that perl debugger relies on "Padwalker".
This release will display a message in the variable inspector in case PadWalker is missing.

Our CI now runs on the package manager "yarn"

src/adapter.ts

@@ -113,6 +113,7 @@ export class perlDebuggerConnection {
 	public perlDebugger: DebugSession;
 	public streamCatcher: StreamCatcher;
 	public perlVersion: string;
+	public padwalkerVersion: string;
 	public commandRunning: string = '';
 
 	private filename?: string;
@@ -362,6 +363,13 @@ export class perlDebuggerConnection {
 			// error on windows
 		}
 
+		try {
+			this.padwalkerVersion = await this.getPadwalkerVersion();
+		} catch(ignore) {
+			// xxx: Ignore errors - it should not break anything, this is used to
+			// inform the user of a missing dependency install of PadWalker
+		}
+
 		return this.parseResponse(data);
 	}
 
@@ -534,6 +542,19 @@ export class perlDebuggerConnection {
 	}
 
 	async variableList(scopes): Promise<ParsedVariableScope> {
+		// If padwalker not found then tell the user via the variable inspection
+		// instead of being empty.
+		if (!this.padwalkerVersion) {
+			return {
+				local_0: [{
+					name: 'PadWalker',
+					value: 'Not installed',
+					type: 'string',
+					variablesReference: '0',
+				}],
+			};
+		}
+
 		const keys = Object.keys(scopes);
 		let result: ParsedVariableScope = {};
 
@@ -589,6 +610,14 @@ export class perlDebuggerConnection {
 		return res.data[0];
 	}
 
+	async getPadwalkerVersion(): Promise<string> {
+		const res = await this.request('print $DB::OUT eval { require PadWalker; PadWalker->VERSION() }');
+		const version = res.data[0];
+		if (/^[0-9]+\.?([0-9]?)+$/.test(version)) {
+			return version;
+		}
+	}
+
 	async resolveFilename(filename): Promise<string> {
 		const res = await this.request(`p $INC{"${filename}"};`);
 		const [ result = '' ] = res.data;

src/localSession.ts

@@ -27,7 +27,7 @@ export class LocalSession implements DebugSession {
 				...options.env,
 			},
 		};
-        // print $DB::OUT eval { require PadWalker; PadWalker->VERSION(0.08) }
+
 		const session = spawn(perlCommand, commandArgs, spawnOptions);
 		this.stdin = session.stdin;
 		this.stdout = session.stdout;

src/tests/connection.test.ts

@@ -264,6 +264,15 @@ describe('Perl debugger connection', () => {
 			});
 		});
 
+		describe('getPadwalkerVersion', () => {
+			it('should return version of installed padwalker', async () => {
+				await conn.launchRequest(FILE_TEST_PL, DATA_ROOT, [], launchOptions);
+				expect(conn.padwalkerVersion).toBeDefined();
+				expect(conn.padwalkerVersion.length).toBeGreaterThan(1);
+				expect(Number(conn.padwalkerVersion)).toBeGreaterThan(1);
+			});
+		});
+
 		describe('getVariableList', () => {
 			it('Should get more scope variables types', async function() {
 				await conn.launchRequest(FILE_TEST_PL, DATA_ROOT, [], launchOptions);