bazelrc: Allow "common" lines to always accept any legal Bazel options

Description of the problem / feature request / question:

Currently, if a bazelrc file contains a common line, then all of the specified options are passed to every bazel command that is run. I propose that the common line always allow all legal options that can apply to any command, but silently ignore the ones that don’t apply to the current command.

The current behavior can easily lead to unnecessary error messages, and greatly hampers the usefulness of the common feature.

For one thing, there are very few Bazel options that are actually common across every command.

Also, although bazelrc supports inheritance (e.g. test and run will automatically inherit from any build lines), that inheritance isn’t always enough. For example, suppose I want to have a custom --package_path for every Bazel command that supports that flag. It’s not sufficient to write

build --package_path ...

because that will apply to build, test, and run, but not to fetch, info, and query, which do not inherit from build but do support the --package_path option.

I could write

build --package_path ...
fetch --package_path ...
info --package_path ...
query --package_path ...

But that is (a) messy, (b) requires me to do a lot of research to carefully figure out which commands support --package_path, and © could break in the future if I upgrade to a newer version of Bazel that supports --package_path for additional commands.

What I really want is to write

common --package_path ...

but I can’t, because that breaks any command that doesn’t support that flag, such as bazel help.

I think probably the best way to address this is what I proposed above: The common line always allows all legal options that can apply to any command, but silently ignores the ones that don’t apply to the current command.

So common --package_path ... would never cause an error, but common --invalid_flag would cause an error.

Environment info

• Operating System:

OS X

• Bazel version (output of bazel info release):

0.4.5

[alexeagle]

I brought up this issue with several groups at BazelCon this year, including the first community day unconference session and the rules authors SIG meeting. There was wide consensus that accidental external repository invalidations and analysis cache discards is a high-priority usability issue. Recent posts on this thread highlight the infeasibility of existing workarounds.

@katre agreed that it’s reasonable to solve this as @mmorearty proposed in the OP: ignore flags that aren’t available on the given command. I believe that is non-breaking for users, since the only behavior change is for bazel invocation that would fail under existing versions of bazel. However he feels that there may be some design discussion required. @gregestren is likely the other expert on this who could help to propose or evaluate designs that can fix it.

[jesseschalken]

My Bash isn’t great but here is a version of @pauldraper 's script that handles inheritance of options between commands.

bazel-option-commands.bash

#!/usr/bin/env bash

set -e -u -o pipefail

# Commands that don't inherit any options
base_commands=(
  analyze-profile
  build
  dump
  fetch
  help
  license
  query
  shutdown
  sync
  version
)

# Commands that inherit options from build
build_commands=(
  aquery
  canonicalize-flags
  clean
  info
  mobile-install
  print_action
  run
  "test"
  # It is not documented that config inherits from build but it does
  config
)

# Commands that inherit options from test
test_commands=(
  coverage
  cquery
)

option="$1"

all_commands_match=true

function command_has_option {
  local help_content
  if ! help_content="$(bazel help --short "$1")"; then
    exit $?
  fi
  grep -qE "^  --(\\[no\\])?$option\$" <<<"$help_content"
}

function test_command {
  if command_has_option "$1"; then
    echo "$1"
  else
    all_commands_match=false
  fi
}

for command in "${base_commands[@]}"; do
  test_command "$command"
done

if ! command_has_option build; then
  for command in "${build_commands[@]}"; do
    test_command "$command"
  done
fi

if ! command_has_option test; then
  for command in "${test_commands[@]}"; do
    test_command "$command"
  done
fi

if [ "$all_commands_match" = true ]; then
  echo "(all commands match, you can put this in \"common\" in .bazelrc)"
fi

$ ./bazel-options-commands.bash workspace_status_command
build

$ ./bazel-options-commands.bash repository_cache
analyze-profile
build
dump
fetch
help
license
query
shutdown
sync
version
(all commands match, you can put this in "common" in .bazelrc)