[PATCH] D65697: [lit] Fix internal env calling internal commands

[Joel E. Denny via Phabricator via llvm-commits]

jdenny created this revision.
jdenny added reviewers: probinson, stella.stamenova, bd1976llvm, jlpeyton, rnk, mgorny.
Herald added a subscriber: delcypher.
Herald added a project: LLVM.

Without this patch, if `env` on a lit RUN line calls `env`, `diff`, or
any of the shell builtins that lit implements, lit accidentally
searches for the latter as an external executable.  What's worse is
that works fine when a developer is testing on a platform where those
executables are available and behave as expected, but it then breaks
on other platforms.

`env` calling `diff` or a shell builtin appears useless in all cases
so far, so this patch takes the safe approach of diagnosing that usage
rather than supporting it.

`env` calling `env` can make sense if one such `env` is within a lit 
substitution, as in D65156 <https://reviews.llvm.org/D65156> and D65121 <https://reviews.llvm.org/D65121>.  This patch ensures that lit 
executes both as internal commands.

This patch also extends lit's test suite to check that lit doesn't
accidentally execute any of those internal commands as external
commands.  It does so by putting fake failing versions of those
commands in `PATH` while the entire lit test suite is running.  For 
some reason I cannot put my finger on, I'm not feeling confident this
testing will behave as I expect on all platforms, so hopefully
reviewers can give advice.  I can say that, without the fixes in the 
rest of this patch but with the tests, this approach does catch 
accidental external calls on my Ubuntu installation.


Repository:
  rG LLVM Github Monorepo

https://reviews.llvm.org/D65697

Files:
  llvm/utils/lit/lit/TestRunner.py
  llvm/utils/lit/tests/Inputs/fake-externals/:
  llvm/utils/lit/tests/Inputs/fake-externals/cd
  llvm/utils/lit/tests/Inputs/fake-externals/diff
  llvm/utils/lit/tests/Inputs/fake-externals/env
  llvm/utils/lit/tests/Inputs/fake-externals/export
  llvm/utils/lit/tests/Inputs/fake-externals/fake-external.py
  llvm/utils/lit/tests/Inputs/fake-externals/mkdir
  llvm/utils/lit/tests/Inputs/fake-externals/rm
  llvm/utils/lit/tests/Inputs/shtest-env/env-calls-cd.txt
  llvm/utils/lit/tests/Inputs/shtest-env/env-calls-colon.txt
  llvm/utils/lit/tests/Inputs/shtest-env/env-calls-diff.txt
  llvm/utils/lit/tests/Inputs/shtest-env/env-calls-echo.txt
  llvm/utils/lit/tests/Inputs/shtest-env/env-calls-env.txt
  llvm/utils/lit/tests/Inputs/shtest-env/env-calls-export.txt
  llvm/utils/lit/tests/Inputs/shtest-env/env-calls-mkdir.txt
  llvm/utils/lit/tests/Inputs/shtest-env/env-calls-rm.txt
  llvm/utils/lit/tests/lit.cfg
  llvm/utils/lit/tests/shtest-env.py

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