[TODO] on error, we shouldn't discard valuable information

[timotheecour]

follow up from #29: my original bug report was actually only half valid / imprecise (sorry for any confusion!); let me clarify what I think is ideal default behavior:

let's reuse bugs/t59_array_index.nim: same as in #29

inim
👑 INim 0.3.1
Nim Compiler Version 0.18.1 [MacOSX: amd64] at /Users/timothee/.nimble/bin/nim
inim> import bugs/t59_array_index
Error: unhandled exception: index out of bounds [IndexError]

the useful context is lost here.

• @["a", "b", "c"] stdout normal output should be shown (but i think that's just on error, should flush stdout #30)
• the error should be:

/Users/timothee/git_clone/nim/timn/bugs/t59_array_index.nim(3) t59_array_index
/Users/timothee/git_clone/nim/Nim/lib/system.nim(3597) []
/Users/timothee/git_clone/nim/Nim/lib/system.nim(2807) sysFatal
Error: unhandled exception: index out of bounds [IndexError]

which shows the relevant useful runtime stacktrace
the only non-relevant information, that we can discard, is:
Error: execution of an external program failed: '/tmp/nim//app '

NOTE: this is also how ipython3 does it.

ipython3
Python 3.6.5 (default, Jun 20 2018, 01:40:23)
Type 'copyright', 'credits' or 'license' for more information
IPython 6.1.0 -- An enhanced Interactive Python. Type '?' for help.

In [1]: import t01_inim_issue_29
['a', 'b', 'c']
a
---------------------------------------------------------------------------
IndexError                                Traceback (most recent call last)
<ipython-input-1-7cfa22fd8457> in <module>()
----> 1 import t01_inim_issue_29

~/git_clone/nim/timn/tests/python/t01_inim_issue_29.py in <module>()
      2 print(a)
      3 print(a[0])
----> 4 print(a[3])
      5

IndexError: list index out of range

• TODO: and in their case, they show more source info which could be nice as an enhancement

NOTE: same with inim -s=bugs/t59_array_index.nim, the useful error should be:

inim -s=bugs/t59_array_index.nim
inim_1531876765
/Users/timothee/git_clone/nim/Nim/lib/system.nim(3597) []
/Users/timothee/git_clone/nim/Nim/lib/system.nim(2807) sysFatal
Error: unhandled exception: index out of bounds [IndexError]

ie, only Error: execution of an external program failed: '/private/tmp/inim_1531876765 ' would be discarded

NOTE: the existing behavior is correct in the following case:

inim
👑 INim 0.3.1
Nim Compiler Version 0.18.1 [MacOSX: amd64] at /Users/timothee/.nimble/bin/nim
inim> asdf
Error: undeclared identifier: 'asdf'
inim>

since there's no relevant stacktrace

summary

• for runtime errors (after compilation of given cmd succeeds and program is ran, then errors), show runtime stacktrace (discard just "Error: execution of an external program failed" which actually isn't even part of runtime error, just the wrapping exec cmd)
• for compile errors, existing behavior (eg just showing: "Error: undeclared identifier: 'asdf'") is problably ok but I need to double check on more complex failures; eg, we problably don't want to filter out "template/generic instantiation from here" compilation error messages since these contain useful information to figure out why compile failed

[AndreiRegiani]

Pushed fixes to master, please check nimble install inim@#head

• Runtime errors show relevant stack trace (4 lines)
• Compilation errors shows single line as before

Works with import foobar, inim -s or inim> .

[timotheecour]

reopening: the following compilation errors are "relevant" and should not be discarded:

bugs/inim/t01_error_msg_discards.nim:

proc fun(a:int):auto =
  a*2
  3

let b=4
echo fun(2)

inim -s=bugs/inim/t01_error_msg_discards.nim --showHeader:false
Error: undeclared identifier: 'a'
inim>

rnim bugs/inim/t01_error_msg_discards.nim
nim c --nimcache:/tmp/nim//nimcache/ -o:/tmp/nim//app -r bugs/inim/t01_error_msg_discards.nim
/Users/timothee/git_clone/nim/timn/bugs/inim/t01_error_msg_discards.nim(1, 1) template/generic instantiation from here
/Users/timothee/git_clone/nim/timn/bugs/inim/t01_error_msg_discards.nim(2, 4) Error: expression 'a * 2' is of type 'int' and has to be discarded
    a*2
     ^

expected output:

inim -s=bugs/inim/t01_error_msg_discards.nim --showHeader:false
/Users/timothee/git_clone/nim/timn/bugs/inim/t01_error_msg_discards.nim(1, 1) template/generic instantiation from here
/Users/timothee/git_clone/nim/timn/bugs/inim/t01_error_msg_discards.nim(2, 4) Error: expression 'a * 2' is of type 'int' and has to be discarded
    a*2
     ^
inim>

[AndreiRegiani]

By compiling your example with Nim 0.18.1 [Linux: amd64] I get:

~ nim c -r bugs/t01_error_msg_discards.nim
Hint: used config file '/home/user/.choosenim/toolchains/nim-#devel/config/nim.cfg' [Conf]
Hint: system [Processing]
Hint: t01_error_msg_discards [Processing]
t01_error_msg_discards.nim(2, 6) Error: expression 'a * 2' is of type 'int' and has to be discarded
~ 

With INim I get same output above:

~ inim -s bugs/t01_error_msg_discards.nim 
👑 INim 0.4.1
Nim Compiler Version 0.18.1 [Linux: amd64] at /home/user/.nimble/bin/nim
inim_1533504761.nim(4, 6) Error: expression 'a * 2' is of type 'int' and has to be discarded
~ 

Since it's the same, does seem good enough to close this issue, what do you think? How did you get the arrow thing?

    a*2
     ^

[timotheecour]

IIRC, --hint[source]=on

btw: IMO if we have to test on only 1 thing, priority should be given to devel, instead of stable

[Tangdongle]

@0atman I think we might be able to close this (unless you think otherwise @timotheecour). Unless I'm doing something wrong, I can't get --hints:on to print out more than INim gives me.