west: runners: jlink: Avoid running logic when another runner is used

The logic to detect the default JLink location was placed at the top of
the script, executing whenever the script was imported. The west
extension command framework loads all runners when initializing, and so
this logic was being executed even when using another runner.

Move the logic to a function that is only executed when the JLink runner
is selected, to avoid executing it at all times.

Signed-off-by: Carles Cufi <carles.cufi@nordicsemi.no>

Author: carlescufi

scripts/west_commands/runners/jlink.py

@@ -26,37 +26,8 @@
 except ImportError:
     MISSING_REQUIREMENTS = True
 
-if sys.platform == 'win32':
-    # JLink.exe can collide with the JDK executable of the same name
-    # Look in the usual locations before falling back to $PATH
-    for root in [os.environ["ProgramFiles"], os.environ["ProgramFiles(x86)"], str(Path.home())]: # noqa SIM112
-        # SEGGER folder can contain a single "JLink" folder
-        _direct = Path(root) / "SEGGER" / "JLink" / "JLink.exe"
-        if _direct.exists():
-            DEFAULT_JLINK_EXE = str(_direct)
-            del _direct
-        else:
-            # SEGGER folder can contain multiple versions such as:
-            #   JLink_V796b
-            #   JLink_V796t
-            #   JLink_V798c
-            # Find the latest version
-            _versions = glob.glob(str(Path(root) / "SEGGER" / "JLink_V*"))
-            if len(_versions) == 0:
-                continue
-            _expected_jlink = Path(_versions[-1]) / "JLink.exe"
-            if not _expected_jlink.exists():
-                continue
-            DEFAULT_JLINK_EXE = str(_expected_jlink)
-            # Cleanup variables
-            del _versions
-            del _expected_jlink
-        break
-    else:
-        # Not found in the normal locations, hope that $PATH is correct
-        DEFAULT_JLINK_EXE = "JLink.exe"
-else:
-    DEFAULT_JLINK_EXE = "JLinkExe"
+# Populated in do_add_parser()
+DEFAULT_JLINK_EXE = None
 DEFAULT_JLINK_GDB_PORT = 2331
 DEFAULT_JLINK_RTT_PORT = 19021
 
@@ -138,8 +109,43 @@ def dev_id_help(cls) -> str:
     def tool_opt_help(cls) -> str:
         return "Additional options for JLink Commander, e.g. '-autoconnect 1'"
 
+    @staticmethod
+    def find_jlink():
+        global DEFAULT_JLINK_EXE
+
+        if sys.platform == 'win32':
+            # JLink.exe can collide with the JDK executable of the same name
+            # Look in the usual locations before falling back to $PATH
+            for root in [os.environ["ProgramFiles"], os.environ["ProgramFiles(x86)"], str(Path.home())]: # noqa SIM112
+                # SEGGER folder can contain a single "JLink" folder
+                _direct = Path(root) / "SEGGER" / "JLink" / "JLink.exe"
+                if _direct.exists():
+                    DEFAULT_JLINK_EXE = str(_direct)
+                else:
+                    # SEGGER folder can contain multiple versions such as:
+                    #   JLink_V796b
+                    #   JLink_V796t
+                    #   JLink_V798c
+                    # Find the latest version
+                    _versions = glob.glob(str(Path(root) / "SEGGER" / "JLink_V*"))
+                    if len(_versions) == 0:
+                        continue
+                    _expected_jlink = Path(_versions[-1]) / "JLink.exe"
+                    if not _expected_jlink.exists():
+                        continue
+                    DEFAULT_JLINK_EXE = str(_expected_jlink)
+                break
+            else:
+                # Not found in the normal locations, hope that $PATH is correct
+                DEFAULT_JLINK_EXE = "JLink.exe"
+        else:
+            DEFAULT_JLINK_EXE = "JLinkExe"
+
     @classmethod
     def do_add_parser(cls, parser):
+
+        cls.find_jlink()
+
         # Required:
         parser.add_argument('--device', required=True, help='device name')