Object protection in BLISS command line

To protect the BLISS shell against unintentional corruption by users and to avoid the loss of object (axes, counters, controllers etc.), that are available in the session environment, a system to protect a subset of these objects is put in place.

By default all objects that are imported from the configuration during the session startup (entries in config-objects and aliases of the session’s yaml configuration) are protected. Further all the content of bliss.shell.standard (e.g. ascan, dscan, wa, umv …) and some globals (ERROR_REPORT, last_error, ALIASES, SCAN_DISPLAY, SCAN_SAVING, SCANS) are protected. However it is possible to modify the behavior during run-time.

When trying the modify an protected object (axis roby in example below) one will see the following message:

TEST_SESSION [1]: roby
         Out [1]: AXIS:
                       name (R): roby
                       unit (R): None
                       offset (R): 0.00000
                       backlash (R): 2.00000
                       sign (R): 1
                       steps_per_unit (R): 10000.00
                       ...

TEST_SESSION [2]: roby = 1
!!! === RuntimeError: roby is protected and can not be modified! === !!! ( for more details type cmd 'last_error()' )

TEST_SESSION [3]: roby
         Out [3]: AXIS:
                       name (R): roby
                       unit (R): None
                       offset (R): 0.00000
                       backlash (R): 2.00000
                       sign (R): 1
                       steps_per_unit (R): 10000.00
                       ...

Protection on runtime

To protect or to remove the protection on the fly the two commands protect and unprotect are available from the command line.

TEST_SESSION [4]: my_important_variable = 3.141
TEST_SESSION [5]: protect('my_important_variable')
TEST_SESSION [6]: my_important_variable
         Out [6]: 3.141

TEST_SESSION [7]: my_important_variable=1
!!! === RuntimeError: my_important_variable is protected and can not be modified! === !!! ( for more details type cmd 'last_error()' )

TEST_SESSION [8]: unprotect('my_important_variable')
TEST_SESSION [9]: my_important_variable=1
TEST_SESSION [10]: my_important_variable
         Out [10]: 1

Customization of protection in session setup .py file

To add additional names to the set of protected keys from the setup file protect method can be used. Note: config objects are protected after setup.

from bliss import is_bliss_shell

my_important_variable = 12

if is_bliss_shell():
    protect('my_important_variable')
    protect(['obj1','obj2'])

Further implementation details

• config.get overrides the protection

  TEST_SESSION [15]: roby
           Out [15]: AXIS:
                          name (R): roby
                          unit (R): None
                          offset (R): 0.00000
                          ...
  
  TEST_SESSION [16]: unprotect('roby')
  TEST_SESSION [17]: roby=1
  TEST_SESSION [18]: protect('roby')
  TEST_SESSION [19]: roby
           Out [19]: 1
  
  TEST_SESSION [20]: config.get('roby')
           Out [20]: AXIS:
                          name (R): roby
                          unit (R): None
                          offset (R): 0.00000
                          ...
  
  TEST_SESSION [21]: roby
           Out [21]: AXIS:
                          name (R): roby
                          unit (R): None
                          offset (R): 0.00000
                          ...
  

• only keys that are present in the env_dict can be protected.
• the use of bliss in library-mode is not concerned, the protection only affects the command line. However, once the command line client is initialized protect and unprotect are available in the session env_dict.