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incompatible_py3_is_default: Bazel configures targets for Python 3 by default #7359
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…t`'s default version When this flag is enabled, `py_binary` and `py_test` targets that do not specify a version (by setting the `python_version` attribute, or its deprecated alias `default_python_version`) will default to `PY3` instead of `PY2`. In addition, the host configuration will use `PY3`, unless `--host_force_python=PY2` is set to override it. The flag requires the new version semantics (`--incompatible_allow_python_version_transitions=true`), and will fail the build if it is not set. The flag is implemented by eliminating PythonVersion#DEFAULT_TARGET_VALUE and replacing it with an accessor PythonOptions#getDefaultPythonVersion. For the case of rule transition factories in rule definitions, which previously relied on DEFAULT_TARGET_VALUE and which do not have access to a configuration, they are updated to instead pass a callback function that retrieves the default version from the configuration at the time of the transition. Work toward #6647, #7359. RELNOTES[INC]: Added --incompatible_py3_is_default to test switching the default Python version to PY3 for py_binary/py_test targets that do not specify a version. See #7359. PiperOrigin-RevId: 232939284
Nice to see this issue. A really good motivation for this issue that is not mentioned could be that Python 2 will reach End of Life in less than 11 months. https://pythonclock.org/ |
Ran a downstream presubmit with this flag and For TensorFlow it didn't actually run the test because it failed a hardcoded version check, and it's not clear that it uses the bazel under test. Filed bazelbuild/continuous-integration#569 for assistance. For the other failures I have no idea whether they're legit or not, and will probably rerun the presubmit to deflake. |
All four of these failures are broken at head. |
It helps if the branch I'm using actually has the flag flips I'm testing. Sigh. Let's do this over again. |
New results here. [Edit: fixed link to show all results]
As of this post rules_typescript and Bazel itself still have a mac test running. In any case, this looks good enough that I'm willing to flip both |
@brandjon This is really promising -- thanks! Does this test exercise rules_docker and, transitively, containerregistry? |
Well I'm not so sure. There is indeed a rules_docker project in the set of downstream tests that get run. But when I tested another flag You can test yourself by grabbing Bazel at head, or a 0.24 RC, and passing (at the same time) --incompatible_py3_is_default and --incompatible_py2_outputs_are_suffixed. You can also check the bazel invocation used in my presubmit and see if any test targets that would've identified problems were missing. |
@brandjon Ahh, right, it looks like google/containerregistry needs a new release with an updated subpar to enable rules_docker and rules_k8s to be updated. |
In another run today, the only failure is in IntelliJ. They're using an output-path-based method for determining whether a Python target is PY2 or PY3. I'm in communication with them to fix. |
Baseline: 235e76b Cherry picks: + badd82e: Automated rollback of commit 1b4c37c. + 33e5719: Fix the Python version select() mechanism to handle PY3-as-default + 56366ee: Set non-empty values for msvc_env_* when VC not installed + 22b3fbf: Windows, test wrapper: fix broken integration test + f14d447: Add whitelist file for starlark transitions + d99bc47: Update BUILD + 3529ad7: Rename tools/function_transition_whitelist/BUILD to tools/whitelists/function_transition_whitelist/BUILD + de0612a: Update bazel_toolchains to latest release and add toolchain config target for BuildKite CI (rbe_ubuntu1604) + 3e660ad: Automated rollback of commit 0877340. + 314cf1f: Pass -undefined dynamic_lookup to dynamic library linking actions on Mac + fc586a8: Move cc_flags target into @bazel_tools//tools/cpp. + ea1703b: C++: Fix crash reported in #7721 + 803801d: Pass execution info to xml generating spawn. Fixes #7794 Incompatible changes: - Added --incompatible_py3_is_default to test switching the default Python version to PY3 for py_binary/py_test targets that do not specify a version. See #7359. - //tools/cmd_line_differ has been renamed to //tools/aquery_differ & can now compare (in addition to command lines) inputs of actions given 2 aquery results. - java_(mutable_|)proto_library: removed strict_deps attribute. - The flag --incompatible_list_based_execution_strategy_selection was added and is used to ease the migration to the new style of specifying execution strategy selection and fallback behavior. The documentation for this flag is here: #7480 - Added --incompatible_py2_outputs_are_suffixed, for switching the bazel-bin symlink to point to Python 3 outputs instead of Python 2 outputs. See [#7593](#7593). New features: - Make actions.args() object chainable. - Added --incompatible_windows_style_arg_escaping flag: enables correct subprocess argument escaping on Windows. (No-op on other platforms.) - Added --incompatible_windows_escape_jvm_flags flag: enables correct java_binary.jvm_flags and java_test.jvm_flags tokenization and escaping on Windows. (No-op on other platforms.) Important changes: - Allow running aquery against the current state of Skyframe - Added support for the "navigation" resource directory to Android resource processing in Bazel. This is used by the Navigation Architecture Component. - --incompatible_disable_runtimes_filegroups was flipped (#6942) - Incompatible flag `--incompatible_linkopts_in_user_link_flags` has been flipped (#6826) - Incompatible flag `--incompatible_dont_emit_static_libgcc` has been flipped (#6825) - --incompatible_disallow_filetype is enabled by default. - Fixed issue where exceptions and stacktraces were silently swallowed in the Android resource processing pipeline. - `--incompatible_disable_expand_if_all_available_in_flag_set` has been flipped (#7008) - --incompatible_disallow_dict_plus is enabled by default - Adds --incompatible_disable_objc_library_resources to disable resource attributes in objc_library. Please migrate these attributes to `data` instead. - --incompatible_disallow_old_style_args_add is enabled by default. - Using the `native` module in BUILD files is deprecated. It will be forbidden with --incompatible_disallow_native_in_build_file. - (Python rules) PyRuntimeInfo is exposed to Starlark, making it possible for Starlark rules to depend on or imitate `py_runtime`. The `files` attribute of `py_runtime` is no longer mandatory. - incompatible_use_toolchain_providers_in_java_common: pass JavaToolchainInfo and JavaRuntimeInfo providers to java_common APIs instead of configured targetshttps://github.com//issues/7186. - is_using_fission crosstool variable is now exposed in all compile actions when fission is active (it used to be exposed only for linking actions). - incompatible_use_toolchain_providers_in_java_common: pass JavaToolchainInfo and JavaRuntimeInfo providers to java_common APIs instead of configured targetshttps://github.com//issues/7186. - `py_runtime` gains a `python_version` attribute for specifying whether it represents a Python 2 or 3 interpreter. - `--incompatible_java_coverage` is enabled by default. - Starlark rules can safely declare attributes named "licenses" - When using --incompatible_list_based_execution_strategy_selection, Bazel will use remote execution by default (if you specify --remote_executor), otherwise persistent workers (if the action supports it), otherwise sandboxed local execution (if the action and platform supports it) and at last unsandboxed local execution. The flags --spawn_strategy and --strategy continue to work as before - this only sets new defaults for the case where you don't specify these flags. - Set default value of --incompatible_remap_main_repo to true. - Set default value of --incompatible_remap_main_repo to true. This release contains contributions from many people at Google, as well as Andrew Suffield, Brandon Lico, Chris Eason, Clint Harrison, Ed Schouten, Garrett Hopper, George Gensure, Greg, John Millikin, Julie, Keith Smiley, Laurent Le Brun, Ryan Beasley, Shmuel H, Travis Cline, Vladimir Chebotarev.
This flag is not actually tested on Bazel CI: Because it relies on
Can we automatically enable |
I manually tested this flag with Bazel 0.24.0 and got the following error
This looks like a bug that has already been fixed at HEAD, but it also means we cannot flip this flag for 0.25.0, because users cannot use 0.24.0 for migration. |
See the link in my last post -- I ran the Bazel CI using the downstream w/ bazel@head pipeline, on a custom build that flipped all four python-version-related flags (2 introduced in 0.23 and 2 in 0.24, all to be flipped in 0.25) and it was green. So I don't think migration is actually an issue for this change. The action conflict issue is partially mitigated by turning on |
Ran another rerun of downstream at head + flag flips here. It's clean except for Tulsi which is broken at Bazel head, and Bazel's own presubmits are still running as I'm writing this. So I'm pretty comfortable with proceeding with these flips. Note that I still have to update Bazels own unit tests for the flag flips. (This isn't reflected by the above presubmit since it modified the host blaze, not the blaze under test.) |
Baseline: 235e76b Cherry picks: + badd82e: Automated rollback of commit 1b4c37c. + 33e5719: Fix the Python version select() mechanism to handle PY3-as-default + 56366ee: Set non-empty values for msvc_env_* when VC not installed + 22b3fbf: Windows, test wrapper: fix broken integration test + f14d447: Add whitelist file for starlark transitions + d99bc47: Update BUILD + 3529ad7: Rename tools/function_transition_whitelist/BUILD to tools/whitelists/function_transition_whitelist/BUILD + de0612a: Update bazel_toolchains to latest release and add toolchain config target for BuildKite CI (rbe_ubuntu1604) + 3e660ad: Automated rollback of commit 0877340. + 314cf1f: Pass -undefined dynamic_lookup to dynamic library linking actions on Mac + fc586a8: Move cc_flags target into @bazel_tools//tools/cpp. + ea1703b: C++: Fix crash reported in #7721 + 803801d: Pass execution info to xml generating spawn. Fixes #7794 Incompatible changes: - Added --incompatible_py3_is_default to test switching the default Python version to PY3 for py_binary/py_test targets that do not specify a version. See #7359. - //tools/cmd_line_differ has been renamed to //tools/aquery_differ & can now compare (in addition to command lines) inputs of actions given 2 aquery results. - java_(mutable_|)proto_library: removed strict_deps attribute. - The flag --incompatible_list_based_execution_strategy_selection was added and is used to ease the migration to the new style of specifying execution strategy selection and fallback behavior. The documentation for this flag is here: #7480 - Added --incompatible_py2_outputs_are_suffixed, for switching the bazel-bin symlink to point to Python 3 outputs instead of Python 2 outputs. See [#7593](#7593). New features: - Make actions.args() object chainable. - Added --incompatible_windows_style_arg_escaping flag: enables correct subprocess argument escaping on Windows. (No-op on other platforms.) - Added --incompatible_windows_escape_jvm_flags flag: enables correct java_binary.jvm_flags and java_test.jvm_flags tokenization and escaping on Windows. (No-op on other platforms.) Important changes: - Allow running aquery against the current state of Skyframe - Added support for the "navigation" resource directory to Android resource processing in Bazel. This is used by the Navigation Architecture Component. - --incompatible_disable_runtimes_filegroups was flipped (#6942) - Incompatible flag `--incompatible_linkopts_in_user_link_flags` has been flipped (#6826) - Incompatible flag `--incompatible_dont_emit_static_libgcc` has been flipped (#6825) - --incompatible_disallow_filetype is enabled by default. - Fixed issue where exceptions and stacktraces were silently swallowed in the Android resource processing pipeline. - `--incompatible_disable_expand_if_all_available_in_flag_set` has been flipped (#7008) - --incompatible_disallow_dict_plus is enabled by default - Adds --incompatible_disable_objc_library_resources to disable resource attributes in objc_library. Please migrate these attributes to `data` instead. - --incompatible_disallow_old_style_args_add is enabled by default. - Using the `native` module in BUILD files is deprecated. It will be forbidden with --incompatible_disallow_native_in_build_file. - (Python rules) PyRuntimeInfo is exposed to Starlark, making it possible for Starlark rules to depend on or imitate `py_runtime`. The `files` attribute of `py_runtime` is no longer mandatory. - incompatible_use_toolchain_providers_in_java_common: pass JavaToolchainInfo and JavaRuntimeInfo providers to java_common APIs instead of configured targetshttps://github.com//issues/7186. - is_using_fission crosstool variable is now exposed in all compile actions when fission is active (it used to be exposed only for linking actions). - incompatible_use_toolchain_providers_in_java_common: pass JavaToolchainInfo and JavaRuntimeInfo providers to java_common APIs instead of configured targetshttps://github.com//issues/7186. - `py_runtime` gains a `python_version` attribute for specifying whether it represents a Python 2 or 3 interpreter. - `--incompatible_java_coverage` is enabled by default. - Starlark rules can safely declare attributes named "licenses" - When using --incompatible_list_based_execution_strategy_selection, Bazel will use remote execution by default (if you specify --remote_executor), otherwise persistent workers (if the action supports it), otherwise sandboxed local execution (if the action and platform supports it) and at last unsandboxed local execution. The flags --spawn_strategy and --strategy continue to work as before - this only sets new defaults for the case where you don't specify these flags. - Set default value of --incompatible_remap_main_repo to true. - Set default value of --incompatible_remap_main_repo to true. This release contains contributions from many people at Google, as well as Andrew Suffield, Brandon Lico, Chris Eason, Clint Harrison, Ed Schouten, Garrett Hopper, George Gensure, Greg, John Millikin, Julie, Keith Smiley, Laurent Le Brun, Ryan Beasley, Shmuel H, Travis Cline, Vladimir Chebotarev.
Baseline: 0366246 Cherry picks: + 3f7f255: Windows: fix native test wrapper's arg. escaping + afeb8d0: Flip --incompatible_windows_escape_jvm_flags + 4299b65: Sort DirectoryNode children to ensure validity. + 231270c: Conditionally use deprecated signature for initWithContentsOfURL + 75a3a53: Add http_archive entries for testing with various JDK versions. + 4a6354a: Now that ubuntu1804 uses JDK 11, remove explicit ubuntu1804_java11 tests. + ae102fb: Fix wrong name of ubuntu1804_javabase9 task. + 0020a97: Remove @executable_path/Frameworks from rpaths + 130f86d: Download stderr/stdout to a temporary FileOutErr Incompatible changes: - (Starlark rules) The legacy "py" provider can no longer be passed to or produced by native Python rules; use [PyInfo](https://docs.bazel.build/versions/master/skylark/lib/PyIn fo.html) instead. See [#7298](#7298) for more information. - (Python rules) The `default_python_version` attribute of the `py_binary` and `py_test` rules has been renamed to `python_version`. Also, the `--force_python` flag has been renamed to `--python_version`. See [#7308](#7308) for more information. - (Python rules) The python version now changes to whatever version is specified in a `py_binary` or `py_test`'s `python_version` attribute, instead of being forced to the value set by a command line flag. You can temporarily revert this change with `--incompatible_allow_python_version_transitions=false`. See [#7307](#7307) for more information. - --incompatible_disable_third_party_license_checking` is enabled by default - Introduced --incompatible_use_python_toolchains, which supersedes --python_top/--python_path. See #7899 and #7375 for more information. - Python 3 is now the default Python version (for `py_binary` and `py_test` targets that don't specify the `python_version` attribute). Targets that are built for Python 3 will no longer have their output put in a separate `-py3` directory; instead there is now a separate `-py2` directory for Python 2 targets. See #7359 and #7593 for more information. - objc_library resource attributes are now disabled by default. Please migrate them to data instead. See #7594 for more info. - Flip --incompatible_windows_escape_jvm_flags to true. See #7486 New features: - genrules now support a $(RULEDIR) variable that resolves to the directory where the outputs of the rule are put. - Added --incompatible_windows_native_test_wrapper flag: enables using the Bash-less test wrapper on Windows. (No-op on other platforms.) Important changes: - incompatible_use_jdk11_as_host_javabase: makes JDK 11 the default --host_javabase for remote jdk (#7219) - Makes genquery somepath output deterministic. - Tristate attributes of native rules now reject True/False (use 1/0) - Rollback of "Tristate attributes of native rules now reject True/False (use 1/0)" - Tristate attributes of native rules now reject True/False (use 1/0) - Added -incompatible_do_not_split_linking_cmdline flag. See #7670 - Tristate attributes of native rules now temporarily accept True/False again - `--incompatible_disable_legacy_crosstool_fields` has been flipped (#6861) `--incompatible_disable_expand_if_all_available_in_flag_set` has been flipped (#7008) - `--incompatible_disable_legacy_crosstool_fields` has been flipped (#6861) `--incompatible_disable_expand_if_all_available_in_flag_set... RELNOTES: None. - --incompatible_no_transitive_loads is enabled by default. - Makes TreeArtifact deterministic. - --incompatible_no_transitive_loads is enabled by default. - Android NDK C++ toolchain is now configured in Starlark. This should be a backwards compatible change, but in case of bugs blame unknown commit. - `--incompatible_disable_legacy_crosstool_fields` has been flipped (#6861) `--incompatible_disable_expand_if_all_available_in_flag_set` has been flipped (#7008) - --incompatible_no_transitive_loads is enabled by default. - --incompatible_bzl_disallow_load_after_statement is enabled - Added `--incompatible_require_ctx_in_configure_features`, see #7793 for details. - Flag --incompatible_merge_genfiles_directory is flipped. This removes the directory `bazel-genfiles` in favor of `bazel-bin`. - previously deprecated flag --experimental_remote_spawn_cache was removed - `--incompatible_disallow_load_labels_to_cross_package_boundaries` is enabled by default - Fix an issue where the Android resource processor did not surface errors from aapt2 compile and link actions. - --incompatible_no_attr_license is enabled by default - `--incompatible_disable_crosstool_file` has been flipped (#7320) - A new flag `--incompatible_string_join_requires_strings` is introduced. The sequence argument of `string.join` must contain only string elements. - --incompatible_symlinked_sandbox_expands_tree_artifacts_in_runfile s_tree has been flipped - Incompatible flag `--incompatible_disable_legacy_cc_provider` has been flipped (see #7036 for details). - Don't drop the analysis cache when the same --define flag is set multiple times and the last value is the same (e.g. if the current invocation was run with "--define foo=bar" and the previous one was run with "--define foo=baz --define foo=bar"). - The --incompatible_disable_genrule_cc_toolchain_dependency flag has been flipped (see #6867 for details). - Incompatible change `--incompatible_remove_cpu_and_compiler_attributes_from_cc_toolcha in` has been flipped (see #7075 for details). - --noexperimental_java_coverage is a no-op flag. - --experimental_java_coverage/--incompatible_java_coverage flag was removed. See #7425. - incompatible_use_toolchain_providers_in_java_common: pass JavaToolchainInfo and JavaRuntimeInfo providers to java_common APIs instead of configured targets (#7186.) - --incompatible_remote_symlinks has been flipped. The remote caching and execution protocol will now represent symlinks in outputs as such. See #7917 for more details. - Bazel is now ~20MiB smaller, from unbundling the Android rules' runtime dependencies. This release contains contributions from many people at Google, as well as Andreas Herrmann, Andrew Suffield, Andy Scott, Benjamin Peterson, Ed Baunton, George Gensure, Ian McGinnis, Ity Kaul, Jingwen Chen, John Millikin, Keith Smiley, Marwan Tammam, Mike Fourie, Oscar Bonilla, perwestling, petros, Robert Sayre, Ryan Beasley, silvergasp, Stanimir Mladenov, Travis Cline, Vladimir Chebotarev, ??.
Baseline: 0366246 Cherry picks: + 3f7f255: Windows: fix native test wrapper's arg. escaping + afeb8d0: Flip --incompatible_windows_escape_jvm_flags + 4299b65: Sort DirectoryNode children to ensure validity. + 231270c: Conditionally use deprecated signature for initWithContentsOfURL + 75a3a53: Add http_archive entries for testing with various JDK versions. + 4a6354a: Now that ubuntu1804 uses JDK 11, remove explicit ubuntu1804_java11 tests. + ae102fb: Fix wrong name of ubuntu1804_javabase9 task. + 0020a97: Remove @executable_path/Frameworks from rpaths + 130f86d: Download stderr/stdout to a temporary FileOutErr Incompatible changes: - (Starlark rules) The legacy "py" provider can no longer be passed to or produced by native Python rules; use [PyInfo](https://docs.bazel.build/versions/master/skylark/lib/PyIn fo.html) instead. See [#7298](#7298) for more information. - (Python rules) The `default_python_version` attribute of the `py_binary` and `py_test` rules has been renamed to `python_version`. Also, the `--force_python` flag has been renamed to `--python_version`. See [#7308](#7308) for more information. - (Python rules) The python version now changes to whatever version is specified in a `py_binary` or `py_test`'s `python_version` attribute, instead of being forced to the value set by a command line flag. You can temporarily revert this change with `--incompatible_allow_python_version_transitions=false`. See [#7307](#7307) for more information. - --incompatible_disable_third_party_license_checking` is enabled by default - Introduced --incompatible_use_python_toolchains, which supersedes --python_top/--python_path. See #7899 and #7375 for more information. - Python 3 is now the default Python version (for `py_binary` and `py_test` targets that don't specify the `python_version` attribute). Targets that are built for Python 3 will no longer have their output put in a separate `-py3` directory; instead there is now a separate `-py2` directory for Python 2 targets. See #7359 and #7593 for more information. - objc_library resource attributes are now disabled by default. Please migrate them to data instead. See #7594 for more info. - Flip --incompatible_windows_escape_jvm_flags to true. See #7486 New features: - genrules now support a $(RULEDIR) variable that resolves to the directory where the outputs of the rule are put. - Added --incompatible_windows_native_test_wrapper flag: enables using the Bash-less test wrapper on Windows. (No-op on other platforms.) Important changes: - incompatible_use_jdk11_as_host_javabase: makes JDK 11 the default --host_javabase for remote jdk (#7219) - Makes genquery somepath output deterministic. - Tristate attributes of native rules now reject True/False (use 1/0) - Rollback of "Tristate attributes of native rules now reject True/False (use 1/0)" - Tristate attributes of native rules now reject True/False (use 1/0) - Added -incompatible_do_not_split_linking_cmdline flag. See #7670 - Tristate attributes of native rules now temporarily accept True/False again - `--incompatible_disable_legacy_crosstool_fields` has been flipped (#6861) `--incompatible_disable_expand_if_all_available_in_flag_set` has been flipped (#7008) - `--incompatible_disable_legacy_crosstool_fields` has been flipped (#6861) `--incompatible_disable_expand_if_all_available_in_flag_set... RELNOTES: None. - --incompatible_no_transitive_loads is enabled by default. - Makes TreeArtifact deterministic. - --incompatible_no_transitive_loads is enabled by default. - Android NDK C++ toolchain is now configured in Starlark. This should be a backwards compatible change, but in case of bugs blame unknown commit. - `--incompatible_disable_legacy_crosstool_fields` has been flipped (#6861) `--incompatible_disable_expand_if_all_available_in_flag_set` has been flipped (#7008) - --incompatible_no_transitive_loads is enabled by default. - --incompatible_bzl_disallow_load_after_statement is enabled - Added `--incompatible_require_ctx_in_configure_features`, see #7793 for details. - Flag --incompatible_merge_genfiles_directory is flipped. This removes the directory `bazel-genfiles` in favor of `bazel-bin`. - previously deprecated flag --experimental_remote_spawn_cache was removed - `--incompatible_disallow_load_labels_to_cross_package_boundaries` is enabled by default - Fix an issue where the Android resource processor did not surface errors from aapt2 compile and link actions. - --incompatible_no_attr_license is enabled by default - `--incompatible_disable_crosstool_file` has been flipped (#7320) - A new flag `--incompatible_string_join_requires_strings` is introduced. The sequence argument of `string.join` must contain only string elements. - --incompatible_symlinked_sandbox_expands_tree_artifacts_in_runfile s_tree has been flipped - Incompatible flag `--incompatible_disable_legacy_cc_provider` has been flipped (see #7036 for details). - Don't drop the analysis cache when the same --define flag is set multiple times and the last value is the same (e.g. if the current invocation was run with "--define foo=bar" and the previous one was run with "--define foo=baz --define foo=bar"). - The --incompatible_disable_genrule_cc_toolchain_dependency flag has been flipped (see #6867 for details). - Incompatible change `--incompatible_remove_cpu_and_compiler_attributes_from_cc_toolcha in` has been flipped (see #7075 for details). - --noexperimental_java_coverage is a no-op flag. - --experimental_java_coverage/--incompatible_java_coverage flag was removed. See #7425. - incompatible_use_toolchain_providers_in_java_common: pass JavaToolchainInfo and JavaRuntimeInfo providers to java_common APIs instead of configured targets (#7186.) - --incompatible_remote_symlinks has been flipped. The remote caching and execution protocol will now represent symlinks in outputs as such. See #7917 for more details. - Bazel is now ~20MiB smaller, from unbundling the Android rules' runtime dependencies. This release contains contributions from many people at Google, as well as Andreas Herrmann, Andrew Suffield, Andy Scott, Benjamin Peterson, Ed Baunton, George Gensure, Ian McGinnis, Ity Kaul, Jingwen Chen, John Millikin, Keith Smiley, Marwan Tammam, Mike Fourie, Oscar Bonilla, perwestling, petros, Robert Sayre, Ryan Beasley, silvergasp, Stanimir Mladenov, Travis Cline, Vladimir Chebotarev, ??.
Flag:
--incompatible_py3_is_default
Available since: 0.24
Will be flipped in: 0.25
Tracking issue: #6647
It is recommended to enable this flag at the same time as
--incompatible_py2_outputs_are_suffixed
.Motivation
Bazel currently defaults to Python 2 due to historic reasons, but the community has largely moved on to Python 3. We should fix this before 1.0.
Note: This incompatible change affects the mechanism that Bazel uses to decide whether a target should be built for Python 2 or 3. However, due to #4815, even when a target is built for Python 3 it may still execute under a Python 2 interpreter. See the workaround using
py_runtime
/--python_top
in #4815 (comment).Change
As of 0.24,
py_binary
andpy_test
targets that do not specify apython_version
attribute (formerly calleddefault_python_version
) will usePY3
instead ofPY2
when--incompatible_py3_is_default
is enabled. In addition,--incompatible_py3_is_default
makes the host configuration usePY3
instead ofPY2
, unless--host_force_python=PY2
is given to override this behavior.--incompatible_py3_is_default
requires that--incompatible_allow_python_version_transitions
is set true, or else an error is raised. This means that if you opt out of--incompatible_allow_python_version_transitions
during the migration window, you should also opt out of--incompatible_py3_is_default
.Migration
Any
py_binary
orpy_test
targets that cannot tolerate Python 3 should have an attributepython_version = "PY2"
added. You can do this with buildozer using a command like the following:For targets that get built in the host configuration, this command can modify their definitions but it will not actually affect the version that they use. If your build has tools in the host configuration that cannot tolerate Python 3, then you can keep the old behavior of using Python 2 for all host configuration targets (across your entire build) by adding
--host_force_python=PY2
to your build invocations. We do not currently have a story for incremental migration of targets in the host configuration to PY3. This is a consequence of the technical limitations of the host configuration, and should be addressed by future work on toolchains.The text was updated successfully, but these errors were encountered: