feat(python): detect python projects with start.py or bot.py (#416)

* feat(python): detect python projects with start.py or bot.py

Refactor Detect() to use getMainPythonFile() instead of duplicating
the sentinel file check. Add start.py to the list of recognized
Python entry files.

Add test case and example for bot.py-only detection.

Fixes PRO-4625

* update

core/__snapshots__/TestGenerateBuildPlanForExamples_python-bot-only_1.snap.json

@@ -0,0 +1,104 @@
+{
+ "deploy": {
+  "base": {
+   "image": "ghcr.io/railwayapp/railpack-runtime:latest"
+  },
+  "inputs": [
+   {
+    "include": [
+     "/mise/shims",
+     "/mise/installs",
+     "/usr/local/bin/mise",
+     "/etc/mise/config.toml",
+     "/root/.local/state/mise"
+    ],
+    "step": "packages:mise"
+   },
+   {
+    "step": "build"
+   },
+   {
+    "exclude": [
+     ".venv"
+    ],
+    "include": [
+     "."
+    ],
+    "step": "build"
+   }
+  ],
+  "startCommand": "python bot.py",
+  "variables": {
+   "PIP_DEFAULT_TIMEOUT": "100",
+   "PIP_DISABLE_PIP_VERSION_CHECK": "1",
+   "PYTHONDONTWRITEBYTECODE": "1",
+   "PYTHONFAULTHANDLER": "1",
+   "PYTHONHASHSEED": "random",
+   "PYTHONUNBUFFERED": "1"
+  }
+ },
+ "steps": [
+  {
+   "assets": {
+    "mise.toml": "[mise.toml]"
+   },
+   "commands": [
+    {
+     "path": "/mise/shims"
+    },
+    {
+     "customName": "create mise config",
+     "name": "mise.toml",
+     "path": "/etc/mise/config.toml"
+    },
+    {
+     "cmd": "mise install",
+     "customName": "install mise packages: python"
+    }
+   ],
+   "inputs": [
+    {
+     "image": "ghcr.io/railwayapp/railpack-builder:latest"
+    }
+   ],
+   "name": "packages:mise",
+   "variables": {
+    "MISE_CACHE_DIR": "/mise/cache",
+    "MISE_CONFIG_DIR": "/mise",
+    "MISE_DATA_DIR": "/mise",
+    "MISE_IDIOMATIC_VERSION_FILE_ENABLE_TOOLS": "python,node,ruby,elixir,go,java,yarn",
+    "MISE_INSTALLS_DIR": "/mise/installs",
+    "MISE_NODE_VERIFY": "false",
+    "MISE_PARANOID": "1",
+    "MISE_PYTHON_COMPILE": "false",
+    "MISE_SHIMS_DIR": "/mise/shims",
+    "MISE_TRUSTED_CONFIG_PATHS": "/app"
+   }
+  },
+  {
+   "inputs": [
+    {
+     "step": "packages:mise"
+    }
+   ],
+   "name": "install"
+  },
+  {
+   "inputs": [
+    {
+     "step": "install"
+    },
+    {
+     "include": [
+      "."
+     ],
+     "local": true
+    }
+   ],
+   "name": "build",
+   "secrets": [
+    "*"
+   ]
+  }
+ ]
+}

core/providers/python/python.go

@@ -31,7 +31,7 @@ func (p *PythonProvider) Initialize(ctx *generate.GenerateContext) error {
 }
 
 func (p *PythonProvider) Detect(ctx *generate.GenerateContext) (bool, error) {
-	hasPython := ctx.App.HasFile("main.py") ||
+	hasPython := p.getMainPythonFile(ctx) != "" ||
 		p.hasRequirements(ctx) ||
 		p.hasPyproject(ctx) ||
 		p.hasPipfile(ctx)
@@ -123,7 +123,7 @@ func (p *PythonProvider) GetStartCommand(ctx *generate.GenerateContext) string {
 }
 
 func (p *PythonProvider) getMainPythonFile(ctx *generate.GenerateContext) string {
-	for _, file := range []string{"main.py", "app.py", "bot.py", "hello.py", "server.py"} {
+	for _, file := range []string{"main.py", "app.py", "start.py", "bot.py", "hello.py", "server.py"} {
 		if ctx.App.HasFile(file) {
 			return file
 		}

core/providers/python/python_test.go

@@ -34,6 +34,11 @@ func TestDetect(t *testing.T) {
 			path: "../../../examples/python-uv",
 			want: true,
 		},
+		{
+			name: "bot.py only",
+			path: "../../../examples/python-bot-only",
+			want: true,
+		},
 		{
 			name: "no python",
 			path: "../../../examples/go-mod",

examples/python-bot-only/bot.py

@@ -0,0 +1 @@
+print("Hello from bot.py")

examples/python-bot-only/test.json

@@ -0,0 +1,5 @@
+[
+  {
+    "expectedOutput": "Hello from bot.py"
+  }
+]