improve 'help'

[jmbarbone]

• help parameter should be able to take a function
• provide better print() for help (below)
• include help in error? or link to execute code?
• apply more coding/cleaning for text
  • skip clean_text() when class is AsIs (i.e., I("my text")
  • line returns are two sequential \n\n, unless wrapped in grave marks
  • clean_padding() should ignore leading and trailing blank/space lines
    • text[grepl("^[[:space:]]{0,}$", text)] <- ""
• $help should be produced when conditions are triggered
  • cnd() should probably contain a withCallingHandlers(), or globalCallingHandlers('cnd::condition' = ...) on .onLoad()

help text should probably use cat(sep = "\n")

cnd:::cond_as_character_condition
#> cnd::condition_generator
#> cnd:as_character_cnd_error/error 
#> 
#> help
#> You cannot coerce a [cnd::condition_generator] object to a character. This may have occurred when trying to put a condition function through [stop()] or [warning].  Instead, call the function first, then pass the result to [stop()] or [warning()].  For example: ```r # Instead of this stop(my_condition)  # Do this stop(my_condition()) ``` 
#> 
#> exports
#>   cnd::condition()

clean_text() should probably incorporate line returns:

do.call(cat, list( cnd:::grey(cnd:::clean_text("this\nthat")), sep = "\n"))
#> this
#> that

[jmbarbone]

There's also the issue of easily being able to write more verbose information

numeric_datetime_tz := condition(
  "Date times cannot be numeric when tz is NULL",
  type = "error",
  exports = "diff_time",
  help = "```r
# Instead of this:
diff_time(100, 200, tz = NULL)

# do this:
diff_time(100, 200, tz = 'America/New_York')

# or:
diff_time(100, 200, tz = 0)
```"
)

which would feel easier to write as:

numeric_datetime_tz := condition(
  "Date times cannot be numeric when tz is NULL",
  type = "error",
  exports = "diff_time",
  help = "
    ```r
    # Instead of this:
    diff_time(100, 200, tz = NULL)
    
    # do this:
    diff_time(100, 200, tz = 'America/New_York')
    
    # or:
    diff_time(100, 200, tz = 0)
    ```
  "
)

but unfortunately, some IDEs may remove the blank spaces, and the documentation retained the tabs

numeric_datetime_tz$help
#> [1] "\n    ```r\n    # Instead of this:\n    diff_time(100, 200, tz = NULL)\n\n    # do this:\n    diff_time(100, 200, tz = 'America/New_York')\n\n    # or:\n    diff_time(100, 200, tz = 0)\n    ```\n   

numeric_datetime_tz$help |> cat()
#>
#>    ```r
#>    # Instead of this:
#>    diff_time(100, 200, tz = NULL)
#>
#>    # do this:
#>    diff_time(100, 200, tz = 'America/New_York')
#>
#>    # or:
#>    diff_time(100, 200, tz = 0)
#>    ```
#>