Simplify slice logic, add tests.

src/phpDebug.ts

@@ -783,13 +783,7 @@ class PhpDebugSession extends vscode.DebugSession {
                 response.body = { stackFrames: [{ id, name, source, line, column: 1 }] }
             } else {
                 const totalFrames = stack.length
-                if (args.levels !== undefined && args.levels > 0) {
-                    stack = stack.filter(
-                        stackFrame =>
-                            stackFrame.level >= (args.startFrame ?? 0) &&
-                            stackFrame.level < (args.startFrame ?? 0) + args.levels!
-                    )
-                }
+                stack = stack.slice(args.startFrame, args.levels ? (args.startFrame ?? 0) + args.levels : undefined)
                 response.body = {
                     totalFrames,
                     stackFrames: stack.map((stackFrame): VSCodeDebugProtocol.StackFrame => {

src/test/adapter.ts

@@ -817,5 +817,24 @@ describe('PHP Debug Adapter', () => {
                 s1.end()
             })
         })
+        it('stack depth', async () => {
+            const program = path.join(TEST_PROJECT, 'stack.php')
+
+            await Promise.all([client.launch({ program }), client.configurationSequence()])
+            const event = (await client.waitForEvent('stopped')) as DebugProtocol.StoppedEvent
+            assert.propertyVal(event.body, 'reason', 'breakpoint')
+            const threadId = event.body.threadId!
+
+            const response = await client.stackTraceRequest({ threadId, levels: 1 })
+            assert.lengthOf(response.body.stackFrames, 1)
+            assert.equal(response.body.totalFrames, 4)
+            assert.equal(response.body.stackFrames[0].name, 'depth3')
+            const response2 = await client.stackTraceRequest({ threadId, startFrame: 1 /*, levels: 3*/ })
+            assert.lengthOf(response2.body.stackFrames, 3)
+            assert.equal(response2.body.totalFrames, 4)
+            assert.equal(response2.body.stackFrames[0].name, 'depth2')
+            assert.equal(response2.body.stackFrames[1].name, 'depth1')
+            assert.equal(response2.body.stackFrames[2].name, '{main}')
+        })
     })
 })

testproject/stack.php

@@ -0,0 +1,17 @@
+<?php
+
+// Test stack depth.
+
+function depth1() {
+	depth2();
+}
+
+function depth2() {
+	depth3();
+}
+
+function depth3() {
+	xdebug_break();
+}
+
+depth1();