DIP41
Contents
DIP 41: dmd command line overhaul. (still editing : don't read yet)
| Title: | dmd command line overhaul. |
|---|---|
| DIP: | 41 |
| Version: | 1 |
| Status: | Draft |
| Created: | 2013-05-20 |
| Last Modified: | 2013-05-20 |
| Author: | Timothee Cour |
| Links: | dmd command line options bad design: -offilename, -Ddocdir etc. |
Abstract
This DIP seeks to improve dmd's command line flags, to make it more consistent with other tools, more expandable, and better interact with other tools such as rdmd.
-offilename vs -of=filename
Dmd currently uses 2 conventions for its flags with arguments:
- type A: -offilename, -Dddocdir, -Dffilename, -Ipath (etc)
- type B: -version=ident (etc)
Type A, the most common in dmd, is problematic:
- it doesn't scale: we can't have any new flag starting with "-I" or "-L", etc as it would create conflicts.
- it's visually harder to tell from the command line the options from the arguments to these options
- it's using a different (worst) convention from most other tools (including other D compilers, like gdc or ldc)
For reference, ldc uses: -of=filename, -Dd=docdir, -Df=filename, -I=path etc.
Deprecation path
We should support type B convention for all flags in a future release of dmd, and support the existing ones for some time until they become deprecated.
1) Make all future flags have type B.
2) Migrate all A flags to B flags.
2a) Here's one possible way to achieve this (say in next dmd release):
dmd -offilename main.d //works but generates a warning for now, and error in a subsequent dmd release
dmd -old_flag -offilename main.d //works and doesn't generate a warning.
dmd -new_flag -of=filename main.d //works. After a certain time passed, -new_flag is implied
Note, A and B flags can't be mixed, eg: -offilename -Ddoc=dir will give error, in all 3 cases above (ie for flags that are currently in the A style).
2b) Alternative: use a new binary name (dmd2, reminds of D2, ldc2, ldmd2) instead of -newflag. I don't like this as much somehow.
Deprecate passing file without extension
I would like to deprecate the current behavior where one can pass the file name without extension (main vs main.d) as source. Consistency is better than avoiding to type those 2 characters. I can create a pathological case where main.d is conflicting with main.d.d (the 2 files have different contents).
rdmd main.d
Which one do you think is called when we call rdmd main.d ? Note, I raised a very analogous concern here [1] regarding naming of object files in a flat hierarchy, see my example with
dmd -c -oq foo/mod.d foo_mod.d
4) The current strategy of rdmd is to treat as input arguments anything after the first source file:
rdmd main.d myfirstprogramarg // a bit awkward, especially with optional extension it gets hard to parse visually.
This is error prone, and inconsistent with dmd's behavior, which is:
dmd src1.d -run main.d myfirstprogramarg //a bit awkward, need to split the source from the main file.
I suggest instead something simpler, explicit and consistent, using -args as a dmd command line argument, that would just work as well with rdmd:
dmd main.d src1.d -args myfirstprogramarg
rdmd main.d -args myfirstprogramarg
5) currently we distinguish rdmd's arguments from dmd's arguments via '--' vs '-'. A better way IMO would be to have a special flag indicating the start of dmd's (or gdc/ldc...) flags: eg
rdmd --chatty --dflags -version=myversion main.d
Notes: Has support of Walter (here)
