shelldriver: make run wrapper injecting more reliable

Current fire and forget approach doesn't work reliably in all corner
cases for various reasons, like for example serial console bitflip or
lost byte issues due to RX fifo overruns. Those issues mostly happen
frequently during early boot process, where there is a lot of output
going on.

So let's make it more reliable by actually checking, if the run wrapper
was injected into the target system correctly.

Signed-off-by: Petr Štetiar <[email protected]>

Author: ynezz

doc/usage.rst

@@ -543,6 +543,7 @@ environment config:
       Mock(return_value=(['OK'], [], 0))
   ).start()
   patch.object(ShellDriver, "_silence_kernel", Mock()).start()
+  patch.object(ShellDriver, "_inject_run", Mock()).start()
 
 .. testcode:: pytest-example
   :hide:

labgrid/driver/shelldriver.py

@@ -239,11 +239,24 @@ def _check_prompt(self):
             self._status = 0
             raise
 
-    def _inject_run(self):
-        self.console.sendline(
-            '''run() { echo -n "$MARKER"; sh -c "$@"; echo "$MARKER $?"; }'''
-        )
-        self.console.expect(self.prompt)
+    def _inject_run(self, inject_timeout=10.0):
+        """Tries to inject run() command wrapper into shell on the console."""
+        timeout = Timeout(inject_timeout)
+
+        while True:
+            self.console.sendline(
+                '''run() { echo -n "$MARKER"; sh -c "$@"; echo "$MARKER $?"; }'''
+            )
+            self.console.expect(self.prompt)
+            try:
+                data = self._raw_run("type run")
+                if data[2] and "function" in data[2]:
+                    return
+            except TIMEOUT:
+                pass
+
+            if timeout.expired:
+                raise TIMEOUT(f"Timeout of {inject_timeout} seconds exceeded during waiting for run injection")  # pylint: disable=line-too-long
 
     @step(args=['keyfile_path'])
     def _put_ssh_key(self, keyfile_path):