Buildozer

Buildozer is a command line tool to rewrite multiple Bazel BUILD files using standard commands.

Installation

1. Build a binary and put it into your $GOPATH/bin:

go install github.com/bazelbuild/buildtools/buildozer@latest

Usage

buildozer [OPTIONS] ['command arg...'...|-f FILE] [label]...

Here, label... is a (space-separated, possibly empty) list of Bazel labels, for example //path/to/pkg1:rule1 relative/path/to/pkg2:rule2. In addition to the Bazel label syntax for specifying a package, Buildozer also allows the package part to refer to a BUILD-like file, for example //WORKSPACE:all or toolchains/BUILD.tpl:host_toolchain.

Buildozer commands are passed as single positional arguments, and thus have to be quoted (or otherwise escaped). Multiple commands and multiple labels can be passed. Buildozer will execute all commands on all targets. (So if you do not specify at least one command and one target, nothing will happen.) Commands are executed in order, files are processed in parallel.

When -f FILE is used instead of literal commands, buildozer reads commands from FILE. FILE can be -, in which case commands are read from the standard input.

The format of the command file is as follows: Empty lines and lines beginning with # are ignored (including leading whitespace). Non-ignored lines consist of |-separated sets of commands and labels:

command arg arg...|command arg arg...|...|label|label|...

(In fact, commands and labels can appear interleaved in arbitrary order.) | characters in commands can be escaped like \|, but double null bytes (\x00\x00) are not valid in command files. See below for special handling of labels to allow reading from the standard input. When a line in a command file uses the single label '*', then the command(s) will be applied to all elements of the list label... from the command line.

Targets

Targets look like Bazel labels, but there can be some differences in presence of macros.

• Use the label notation to refer to a rule: //buildtools/buildozer:edit
• Use the __pkg__ suffix to refer to the package declaration: //buildtools/buildozer:__pkg__
• Use an asterisk to refer to all rules in a file: //pkg:*
• Use ... to refer to all descendant BUILD files in a directory: //pkg/...:*
• Use percent to refer to all rules of a certain kind: //pkg:%java_library
• Use percent-and-number to refer to a rule that begins at a certain line: //pkg:%123.
• Use the special package name - to read the BUILD file from the standard input instead of from a local file in the package directory: -:all_tests. (It is presumably not useful to both use a - package name and use the -f - flag to read commands from the standard input.)

Options

OPTIONS include the following options:

• -stdout : write changed BUILD file to stdout
• -buildifier : format output using a specific buildifier binary. If empty, use built-in formatter.
• -k : apply all commands, even if there are failures
• -quiet : suppress informational messages
• -shorten_labels : convert added labels to short form, e.g. //foo:bar => :bar
• -types: Filter the targets, keeping only those of the given types, e.g. buildozer -types go_library,go_binary 'print rule' '//buildtools/buildozer:*'
• -eol-comments=false: When adding new comments, put them on a separate line.

See buildozer -help for the full list.

Edit commands

Buildozer supports the following commands('command args'):

• add <attr> <value(s)>: Adds value(s) to a list attribute of a rule. If a value is already present in the list, it is not added.
• new_load <path> <[to=]from(s)>: Add a load statement for the given path, importing the symbols. Before using this, make sure to run buildozer 'fix movePackageToTop'. Afterwards, consider running buildozer 'fix unusedLoads'.
• replace_load <path> <[to=]from(s)>: Similar to new_load, but removes existing load statements for the requested symbols before adding new loads.
• substitute_load <old_regexp> <new_template> Replaces modules of loads which match old_regexp according to new_template. The regular expression must follow RE2 syntax. new_template may be a simple replacement string, but it may also expand numbered or named groups using $0 or $x.
• comment <attr>? <value>? <comment>: Add a comment to a rule, an attribute, or a specific value in a list. Spaces in the comment should be escaped with backslashes.
• print_comment <attr>? <value>?
• delete: Delete a rule.
• fix <fix(es)>?: Apply a fix.
• move <old_attr> <new_attr> <value(s)>: Moves value(s) from the list old_attr to the list new_attr. The wildcard * matches all values.
• new <rule_kind> <rule_name> [(before|after) <relative_rule_name>]: Add a new rule at the end of the BUILD file (before/after <relative_rule>). The identifier __pkg__ can be used to position rules relative to package().
• print <attr(s)>
• remove <attr>: Removes attribute attr. The wildcard * matches all attributes except name.
• remove <attr> <value(s)>: Removes value(s) from the list attr. The wildcard * matches all attributes. Lists containing none of the value(s) are not modified.
• remove_comment <attr>? <value>?: Removes the comment attached to the rule, an attribute, or a specific value in a list.
• remove_if_equal <attr> <value>: Removes the attribute attr if its value is equal to value.
• rename <old_attr> <new_attr>: Rename the old_attr to new_attr which must not yet exist.
• replace <attr> <old_value> <new_value>: Replaces old_value with new_value in the list attr. Wildcard * matches all attributes. Lists not containing old_value are not modified.
• substitute <attr> <old_regexp> <new_template>: Replaces strings which match old_regexp in the list attr according to new_template. Wildcard * matches all attributes. The regular expression must follow RE2 syntax. new_template may be a simple replacement string, but it may also expand numbered or named groups using $0 or $x. Lists without strings that match old_regexp are not modified.
• set <attr> <value(s)>: Sets the value of an attribute. If the attribute was already present, its old value is replaced.
• set_if_absent <attr> <value(s)>: Sets the value of an attribute. If the attribute was already present, no action is taken.
• set kind <value>: Set the target type to value.
• set_select <attr> <key_1> <value_1> <key_n> <value_n>
• copy <attr> <from_rule>: Copies the value of attr between rules. If it exists in the to_rule, it will be overwritten.
• copy_no_overwrite <attr> <from_rule>: Copies the value of attr between rules. If it exists in the to_rule, no action is taken.
• dict_add <attr> <(key:value)(s)>: Sets the value of a key for the dict attribute attr. If the key was already present, it will not be overwritten
• dict_set <attr> <(key:value)(s)>: Sets the value of a key for the dict attribute attr. If the key was already present, its old value is replaced.
• dict_remove <attr> <key(s)>: Deletes the key for the dict attribute attr.
• dict_replace_if_equal <attr> <key> <old_value> <new_value>: Replaces old_value with new_value for key key in dictionary attribute attr. If the key is not present in the dictionary, or does not have value old_value, it will not be updated.
• dict_list_add <attr> <key> <value(s)>: Adds value(s) to the list in the dict attribute attr.
• format: Force formatting of all files, even if they were not changed by other commands.

Here, <attr> represents an attribute (being added/renamed/deleted etc.), e.g.: srcs, <value(s)> represents values of the attribute and so on. A '?' indicates that the preceding argument is optional.

The fix command without a fix specified applied to all eligible fixes. Use //path/to/pkg:__pkg__ as label for file level changes like new_load and new. A transformation can be applied to all rules of a particular kind by using %rule_kind at the end of the label(see examples below).

The following commands only apply to MODULE.bazel files (e.g. the target //MODULE.bazel:all):

• use_repo_add <use_extension variable name> <repo(s)>: Ensures that the given repositories are imported via use_repo for the extension for which the given top-level variable contains the return value of a use_extension call.
• use_repo_remove <use_extension variable name> <repo(s)>: Ensures that the given repositories are not imported via use_repo for the extension for which the given top-level variable contains the return value of a use_extension call.
• use_repo_add [dev] <extension .bzl file> <extension name> <repo(s)>: Ensures that the given repositories generated by the given extension are imported via use_repo. If the dev argument is given, extension usages with dev_dependency = True will be considered instead. Extension usages with isolated = True are ignored.
• use_repo_remove [dev] <extension .bzl file> <extension name> <repo(s)>: Ensures that the given repositories generated by the given extension are not imported via use_repo. If the dev argument is given, extension usages with dev_dependency = True will be considered instead. Extension usages with isolated = True are ignored.

Examples

# Edit //pkg:rule and //pkg:rule2, and add a dependency on //base
buildozer 'add deps //base' //pkg:rule //pkg:rule2

# A load for a skylark file in //pkg
buildozer 'new_load //tools/build_rules:build_test.bzl build_test' //pkg:__pkg__

# Replaces existing loads for build_test in //pkg
buildozer 'replace_load @rules_build//build:defs.bzl build_test' //pkg:__pkg__

# Replaces modules of loads using regular expressions.
#
# In this example
#     load("@rules_foo//foo:defs.bzl", "foo_library", "foo_test")
# will be replaced with
#     load("//third_party/build_defs/rules_foo/foo:defs.bzl", "foo_library", "foo_test")
buildozer 'substitute_load ^@([^/]*)//([^:].*)$ //third_party/build_defs/${1}/${2}' //pkg:__pkg__

# Change the default_visibility to public for the package //pkg
buildozer 'set default_visibility //visibility:public' //pkg:__pkg__

# Change all gwt_module targets to java_library in the package //pkg
buildozer 'set kind java_library' //pkg:%gwt_module

# Replace the dependency on pkg_v1 with a dependency on pkg_v2
buildozer 'replace deps //pkg_v1 //pkg_v2' //pkg:rule

# Replace all dependencies using regular expressions.
buildozer 'substitute deps //old/(.*) //new/${1}' //pkg:rule

# Delete the dependency on foo in every cc_library in the package
buildozer 'remove deps foo' //pkg:%cc_library

# Delete the testonly attribute in every rule in the package
buildozer 'remove testonly' '//pkg:*'

# Add a comment to the timeout attribute of //pkg:rule_test
buildozer 'comment timeout Delete\ this\ after\ 2015-12-31.' //pkg:rule_test

# Add a new rule at the end of the file
buildozer 'new java_library foo' //pkg:__pkg__

# Add a cc_binary rule named new_bin before the rule named tests
buildozer 'new cc_binary new_bin before tests' //:__pkg__

# Copy an attribute from `protolib` to `py_protolib`.
buildozer 'copy testonly protolib' //pkg:py_protolib

# Set two attributes in the same rule
buildozer 'set compile 1' 'set srcmap 1' //pkg:rule

# Make a default explicit in all soy_js rules in a package
buildozer 'set_if_absent allowv1syntax 1' //pkg:%soy_js

# Add an attribute new_attr with value "def_val" to all cc_binary rules
# Note that special characters will automatically be escaped in the string
buildozer 'add new_attr def_val' //:%cc_binary

Print commands

These commands are not modifying files, Buildifier returns 0 after a successful execution.

• print <attribute(s)>: For each target, prints the value of the attributes (see below).
• print_comment <attr>? <value>?: Prints a comment associated with a rule, an attribute or a specific value in a list.

The print command prints the value of the attributes. If a target doesn't have the attribute, a warning is printed on stderr.

There are some special attributes in the print command:

• kind: displays the name of the function
• label: the fully qualified label
• rule: the entire rule definition
• startline: the line number on which the rule begins in the BUILD file
• endline: the line number on which the rule ends in the BUILD file
• path: the absolute path to the BUILD file that contains the rules

Examples

# Print the kind of a target
buildozer 'print kind' base  # output: cc_library

# Print the name of all cc_library in //base
buildozer 'print name' base:%cc_library

# Get the default visibility of the //base package
buildozer 'print default_visibility' base:%package

# Print labels of cc_library targets in //base that have a deps attribute
buildozer 'print label deps' base:%cc_library 2>/dev/null | cut -d' ' -f1

# Print the list of labels in //base that explicitly set the testonly attribute:
buildozer 'print label testonly' 'base:*' 2>/dev/null

# Print the entire definition (including comments) of the //base:heapcheck rule:
buildozer 'print rule' //base:heapcheck

Converting labels

Buildozer works at the syntax-level. It doesn't evaluate the BUILD files. If you need to query the information Bazel has, please use bazel query. If you have a list of Bazel labels, chances are that some of them are generated by BUILD extensions. Labels in Buildozer are slightly different from labels in Bazel. Bazel cares about the generated code, while Buildozer looks at the BUILD file before macro expansion.

To see the expanded BUILD files, try:

bazel query --output=build //path/to/BUILD

Do multiple changes at once

Use buildozer -f <file> to load a list of commands and labels from a file (see Usage above).

$ cat /tmp/cmds
# a comment
new cc_library foo|//buildtools/buildozer/BUILD
add deps //base //strings|add srcs foo.cc|//buildtools/buildozer:foo
add deps :foo|//buildtools/buildozer

$ buildozer -f /tmp/cmds
fixed //buildtools/buildozer/BUILD

The list of commands will typically be generated and can be large. This is efficient: Commands are grouped so that each file is modified once. Files are processed in parallel.

Alternatively, BUILD files can be read from the standard input and written to the standard output, by using the - package name:

$ cat /tmp/cmds
add deps //base //strings|-:foo|-:bar

$ cat some/path/BUILD | buildozer -f /tmp/cmds

This writes the result of updating the :foo and :bar targets in the input BUILD file to the standard output.

Buildozer commands can be made executable by means of a shebang line, too:

#!/usr/bin/env -S buildozer -f
#
# Adds //base and //string dependencies to :foo and :bar.

add deps //base //strings|-:foo|-:bar

Error code

The return code is:

• 0 on success, if changes were made or only readonly commands were executed
• 1 when there is a usage error
• 2 when at least one command has failed
• 3 on success, when no changes were made

Source Structure

• buildozer/main.go : Entry point for the buildozer binary
• edit/buildozer.go : Implementation of functions for the buildozer commands
• edit/edit.go: Library functions to perform various operations on ASTs. These
• functions are called by the impl functions in buildozer.go
• edit/fix.go: Functions for various fixes for the buildozer 'fix <fix(es)>' command, like cleaning unused loads, changing labels to canonical notation, etc.
• edit/types.go: Type information for attributes