[lit] Remove TODO

[modocache]

Summary

Instead of keeping track of TODOs for lit in a file checked into source
control, use LLVM's bug tracker. The TODOs have been migrated to the
following bugs:

• https://llvm.org/bugs/show_bug.cgi?id=30666
• https://llvm.org/bugs/show_bug.cgi?id=30667
• https://llvm.org/bugs/show_bug.cgi?id=30668
• https://llvm.org/bugs/show_bug.cgi?id=30669
• https://llvm.org/bugs/show_bug.cgi?id=30670
• https://llvm.org/bugs/show_bug.cgi?id=30671

[modocache]

Update the README

[delcypher]

@modocache Sorry for the delay in taking a look at this.

This change mostly LGTM except it looks like you've dropped these TODOs

* Move temp directory name into local test config.

* Support valgrind in all configs, and LLVM style valgrind.

* Support ulimit.

* Create an explicit test suite object (instead of using the top-level TestingConfig object).

Is that intentional?

[modocache]

• "Move temp directory name into local test config" has been moved to https://llvm.org/bugs/show_bug.cgi?id=30673. Based on the comment on that bug, it may already be done!
• "Support ulimit" has been moved to https://llvm.org/bugs/show_bug.cgi?id=30672.

As for the others:

• I chose not to migrate "Create an explicit test suite object (instead of using the top-level TestingConfig object)" because I wasn't sure it was still relevant. It also seems like an implementation detail to me.
• I'd appreciate it if you could create a problem report for "Support valgrind in all configs, and LLVM style valgrind", @delcypher! I'm not sure I understand what is and isn't supported.

[delcypher]

@modocache

I'd appreciate it if you could create a problem report for "Support valgrind in all configs, and LLVM style valgrind", @delcypher! I'm not sure I understand what is and isn't supported.

I'm not entirely sure what this is either. lit can run tools under valgrind but I'm not sure if valgrind is actively used much these days for LLVM development. There are valgrind suppression files in the LLVM source tree (utils/valgrind) but they haven't been touched in a while but I'm guessing that's what this TODO was referring to. Really the idea of running the tests with a supervising tool needs to be generalized so arbitary stuff can be plugged in. For example it might be useful to have the system debugger attached to every process spawned so if one of them crashes it's easy to see what happened.

I could create a problem report for that if you like.

Also sorry for my slowness in replying :(

[modocache]

Thanks @delcypher! No worries about any lateness, I really appreciate the review!

A problem report for Valgrind would be appreciated, even if it's just "figure out what that old TODO was referring to." :)

utils/lit/README.txt

 ===============================
  lit - A Software Testing Tool
 ===============================
 
 lit is a portable tool for executing LLVM and Clang style test suites,
 summarizing their results, and providing indication of failures. lit is designed
 to be a lightweight testing tool with as simple a user interface as possible.
 
 =====================
  Contributing to lit
 =====================
 
-Please read the TODO file in this directory for ideas on what to work on.
+Please browse the Test Suite > lit category in LLVM's Bugzilla for ideas on
+what to work on.
+
 Before submitting patches, run the test suite to ensure nothing has regressed:
 
     # From within your LLVM source directory.
     utils/lit/lit.py \
         --path /path/to/your/llvm/build/bin \
         utils/lit/tests
 
 Note that lit's tests depend on 'not' and 'FileCheck', LLVM utilities.
 You will need to have built LLVM tools in order to run lit's test suite
 successfully.
 

utils/lit/TODO

-================
- lit TODO Items
-================
-
-Infrastructure
-==============
-
-1. Change to always load suites, then resolve command line arguments?
-
-  Currently we expect each input argument to be a path on disk; we do a
-  recursive search to find the test suite for each item, but then we only do a
-  local search based at the input path to find tests. Additionally, for any path
-  that matches a file on disk we explicitly construct a test instance (bypassing
-  the formats on discovery implementation).
-
-  This has a couple problems:
-
-  * The test format doesn't have control over the test instances that result
-    from file paths.
-
-  * It isn't possible to specify virtual tests as inputs. For example, it is not
-    possible to specify an individual subtest to run with the googletest format.
-
-  * The test format doesn't have full control over the discovery of tests in
-    subdirectories.
-
-  Instead, we should move to a model whereby first all of the input specifiers
-  are resolved to test suites, and then the resolution of the input specifier is
-  delegated to each test suite. This could take a couple forms:
-
-  * We could resolve to test suites, then fully load each test suite, then have
-    a fixed process to map input specifiers to tests in the test suite
-    (presumably based on path-in-suite derivations). This has the benefit of
-    being consistent across all test formats, but the downside of requiring
-    loading the entire test suite.
-
-  * We could delegate all of the resolution of specifiers to the test
-    suite. This would allow formats that anticipate large test suites to manage
-    their own resolution for better performance. We could provide a default
-    resolution strategy that was similar to what we do now (start at subpaths
-    for directories, but allow the test format control over what happens for
-    individual tests).
-
-2. Consider move to identifying all tests by path-to-test-suite and then path to
-   subtest, and don't use test suite names.
-
-  Currently the test suite name is presented as part of test names, but it has
-  no other useful function, and it is something that has to be skipped over to
-  cut-and-paste a name to subsequently use to rerun a test. If we just
-  represented each test suite by the path to its suite, then it would allow more
-  easy cut-and-paste of the test output lines. This has the downside that the
-  lines might get rather long.
-
-3. Allow 'lit' driver to cooperate with test formats and suites to add options
-   (or at least sanitize accepted params).
-
-  We have started to use the --params method more and more extensively, and it is
-  cumbersome and error prone. Additionally, there are currently various options
-  ``lit`` honors that should more correctly be specified as belonging to the
-  ShTest test format.
-  
-  It would be really nice if we could allow test formats and test suites to add
-  their own options to be parsed. The difficulty here, of course, is that we
-  don't know what test formats or test suites are in use until we have parsed the
-  input specifiers. For test formats we could ostensibly require all the possible
-  formats to be registered in order to have options, but for test suites we would
-  certainly have to load the suite before we can query it for what options it
-  understands.
-
-  That leaves us with the following options:
-
-  * Currently we could almost get away with parsing the input specifiers without
-    having done option parsing first (the exception is ``--config-prefix``) but
-    that isn't a very extensible design.
-
-  * We could make a distinction in the command line syntax for test format and
-    test suite options. For example, we could require something like::
-
-      lit -j 1 -sv input-specifier -- --some-format-option
-
-    which would be relatively easy to implement with optparser (I think).
-
-  * We could allow fully interspersed arguments by first extracting the options
-    lit knows about and parsing them, then dispatching the remainder to the
-    formats. This seems the most convenient for users, who are unlikely to care
-    about (or even be aware of) the distinction between the generic lit
-    infrastructure and format or suite specific options.
-
-4. Eliminate duplicate execution models for ShTest tests.
-
-  Currently, the ShTest format uses tests written with shell-script like syntax,
-  and executes them in one of two ways. The first way is by converting them into
-  a bash script and literally executing externally them using bash. The second
-  way is through the use of an internal shell parser and shell execution code
-  (built on the subprocess module). The external execution mode is used on most
-  Unix systems that have bash, the internal execution mode is used on Windows.
-
-  Having two ways to do the same thing is error prone and leads to unnecessary
-  complexity in the testing environment. Additionally, because the mode that
-  converts scripts to bash doesn't try and validate the syntax, it is possible
-  to write tests that use bash shell features unsupported by the internal
-  shell. Such tests won't work on Windows but this may not be obvious to the
-  developer writing the test.
-
-  Another limitation is that when executing the scripts externally, the ShTest
-  format has no idea which commands fail, or what output comes from which
-  commands, so this limits how convenient the output of ShTest failures can be
-  and limits other features (for example, knowing what temporary files were
-  written).
-
-  We should eliminate having two ways of executing the same tests to reduce
-  platform differences and make it easier to develop new features in the ShTest
-  module. This is currently blocked on:
-
-  * The external execution mode is faster in some situations, because it avoids
-    being bottlenecked on the GIL. This can hopefully be obviated simply by
-    using --use-processes.
-
-  * Some tests in LLVM/Clang are explicitly disabled with the internal shell
-    (because they use features specific to bash). We would need to rewrite these
-    tests, or add additional features to the internal shell handling to allow
-    them to pass.
-
-5. Consider changing core to support setup vs. execute distinction.
-
-  Many of the existing test formats are cleanly divided into two phases, once
-  parses the test format and extracts XFAIL and REQUIRES information, etc., and
-  the other code actually executes the test.
-
-  We could make this distinction part of the core infrastructure and that would
-  enable a couple things:
-
-  * The REQUIREs handling could be lifted to the core, which is nice.
-
-  * This would provide a clear place to insert subtest support, because the
-    setup phase could be responsible for providing subtests back to the
-    core. That would provide part of the infrastructure to parallelize them, for
-    example, and would probably interact well with other possible features like
-    parameterized tests.
-
-  * This affords a clean implementation of --no-execute.
-
-  * One possible downside could be for test formats that cannot determine their
-    subtests without having executed the test. Supporting such formats would
-    either force the test to actually be executed in the setup stage (which
-    might be ok, as long as the API was explicitly phrased to support that), or
-    would mean we are forced into supporting subtests as return values from the
-    execute phase.
-
-  Any format can just keep all of its code in execute, presumably, so the only
-  cost of implementing this is its impact on the API and futures changes.
-
-
-Miscellaneous
-=============
-
-* Move temp directory name into local test config.
-
-* Support valgrind in all configs, and LLVM style valgrind.
-
-* Support ulimit.
-
-* Create an explicit test suite object (instead of using the top-level
-  TestingConfig object).
-
-* Introduce a wrapper class that has a ``subprocess.Popen`` like interface
-  but also supports killing the process and all its children and use this for
-  running tests.  This would allow us to implement platform specific methods
-  for killing a process's children which is needed for a per test timeout. On
-  POSIX platforms we can use process groups and on Windows we can probably use
-  job objects. This would not only allow us to remove the dependency on the
-  ``psutil`` module but would also be more reliable as the
-  ``lit.util.killProcessAndChildren()`` function which is currently used is
-  potentially racey (e.g. it might not kill a fork bomb completely).