Template language changes

[chaley]

Kovid accepted the changes. They are in calibre source, available to testing/inspection.

[chaley]

I am considering adding a 'break' statement to the template language to exit for loops. To do so I must make it a reserved word.

By way of a survey, do any of you have template local variables named 'break'? This change would require renaming them.

[ownedbycats]

I do not use it; if I ever felt the need to, I could just use "br" instead.

btw, thanks for the word wrap!

[capink]

Originally Posted by chaley

I am considering adding a 'break' statement to the template language to exit for loops. To do so I must make it a reserved word.

By way of a survey, do any of you have template local variables named 'break'? This change would require renaming them.

Yes please. I ran into multiple situations that would have been much easier with this feature. Would you also add 'continue' to this?

[davidfor]

Originally Posted by chaley

I am considering adding a 'break' statement to the template language to exit for loops. To do so I must make it a reserved word.

By way of a survey, do any of you have template local variables named 'break'? This change would require renaming them.

Yes please. I doubt if I have used "break" as a variable name. I think it is to ingrained in me after C, C++, C#, Python and probably other languages. Which is a problem when writing Perl at work

Are you also adding "continue"?

[chaley]

06 Apr 2021 (in calibre version 5.15)

• Add 'break' and 'continue' to the template language.
• Add a "Test" button to the Stored Templates preferences dialog.
  Clicking this button opens a subsidiary template tester that can 'see' the templates being created/edited in the preferences dialog, where you can write a template that test the stored templates. It shows the values using the books selected before starting the preferences dialog.
• Make TAB and SHIFT-TAB indent and unindent selected lines in the template tester.
• Add template file load/save buttons and to the template tester context menu. The buttons and the context menu items do the same thing.
• Add the ability to toggle word wrapping to the template tester context menu.
• Make the top button line reflow to two lines if the dialog box isn't wode enough

[chaley]

12 Apr 2021 (in calibre version 5.15)

• Add 'return expression' to the template language. The expression doesn't need to be in parentheses.
• Improve syntax and runtime error messages
• Fix not using metadata from the selected book when breakpointing.
• Improved help text in the Stored Template dialog.
• Allow hiding the help text in the Stored Template dialog.

[chaley]

14 Apr 2021 (in calibre version 5.15)

• Add the infix operator 'pattern inlist list'. It returns True ('1') if the regular expression pattern matches any item in the comma-separated list, otherwise False ('').

[chaley]

18 April 2021 (In calibre version 5.16.1)

• Fix a regression in calibre version 5.15 that broke stored templates. They always raise an exception.
• Add a tweak "Tab stop width in the template editor (ID: template_editor_tab_stop_width)" to control the width of tab stops in the template editor. The default is now 4 average-size characters.

[ownedbycats]

Originally Posted by chaley

18 April 2021 (In calibre source)

• Fix a regression in calibre version 5.15 that broke stored templates. They always raise an exception.
• Add a tweak "Tab stop width in the template editor (ID: template_editor_tab_stop_width)" to control the width of tab stops in the template editor. The default is now 4 average-size characters.

Is the first one why 5.16 was released so quickly?

[chaley]

Originally Posted by ownedbycats

Is the first one why 5.16 was released so quickly?

No. It is still broken in 5.16. I just noticed it today.

We haven't had any bug reports, which says something about stored template usage.

[ownedbycats]

I meant to implement one for my shared emblem/icon rules, but never got around to it.

[chaley]

21 April 2021 (In calibre version 5.17)

• Add the function "character('character_name')" that returns the special character named by character_name. For example, character('newline') returns a newline character ('\n'). The function can be used with strcat() to create multiline and tab-aligned output. The supported character names are 'newline', 'return', 'tab', and 'backslash'. The argument to character() can be an expression that returns the character name.
• Show special characters in the template editor & debugger as escape sequences, e.g., a newline is displayed as \n.
• Performance improvements in the template language parser.

[chaley]

3 June 2021 (In calibre version 5.21)

• Add the function date_arithmetic(date, calc_spec, fmt) to simplify computing new dates from existing ones. The documentation for the function is

  date_arithmetic(date, calc_spec, fmt) -- Calculate a new date from 'date' using 'calc_spec'. Return the new date formatted according to optional 'fmt'; if not supplied then the result will be in ISO format. The calc_spec is a string formed by concatenating pairs of 'vW' ('valueWhat') where 'v' is a possibly-negative number and W is one of the following letters:

  • 's': add 'v' seconds to 'date'
  • 'm': add 'v' minutes to 'date'
  • 'h': add 'v' hours to 'date'
  • 'd': add 'v' days to 'date'
  • 'w': add 'v' weeks to 'date'
  • 'y': add 'v' years to 'date', where a year is 365 days.

  Example: '1s3d-1m' will add 1 second, add 3 days, and subtract 1 minute from 'date'.

  NB: you probably want to use a raw_field() or '$$date' to fetch the source date so you can be sure that all the fields are there.
  
  And yes, the 'months' specifier is missing, because the number of days in a month depend on both the source date month and year. This is also why a year is fixed at 365 days.

[ownedbycats]

That will be helpful.