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diff --git a/doc/PROGRAMMING b/doc/PROGRAMMING new file mode 100644 index 0000000..97cd40e --- /dev/null +++ b/doc/PROGRAMMING @@ -0,0 +1,598 @@ +This file documents things you should know to write a new debhelper program. +Any program with a name that begins with dh_ should conform to these +guidelines (with the historical exception of dh_make). + +Standardization: +--------------- + +There are lots of debhelper commands. To make the learning curve shallower, +I want them all to behave in a standard manner: + +All debhelper programs have names beginning with "dh_". This is so we don't +pollute the name space too much. + +Debhelper programs should never output anything to standard output except +error messages, important warnings, and the actual commands they run that +modify files under debian/ (this last only if they are passed -v, and if you +output the commands, you should indent them with 1 tab). This is so we don't +have a lot of noise output when all the debhelper commands in a debian/rules +are run, so the important stuff is clearly visible. + +An exception to above rule are dh_auto_* commands and dh itself. They will +also print the commands interacting with the upstream build system and which +of the simple debhelper programs are called. (i.e. print what a traditional +non-dh(1) using debian/rules would print but nothing else). + +Debhelper programs should accept all options listed in the "SHARED +DEBHELPER OPTIONS" section of debhelper(7), including any long forms of +these options, like --verbose . If necessary, the options may be ignored. + +If debhelper commands need config files, they should use +debian/package.filename as the name of the config file (replace filename +with whatever your command wants), and debian/filename should also be +checked for config information for the first binary package in +debian/control. Also, debhelper commands should accept the same sort of +information that appears in the config files, on their command lines, if +possible, and apply that information to the first package they act on. +The config file format should be as simple as possible, generally just a +list of files to act on. + +Debhelper programs should never modify the debian/postinst, debian/prerm, +etc scripts. Instead, they can add lines to debian/postinst.debhelper, etc. +The autoscript() function (see below) is one easy way to do this. +dh_installdeb is an exception, it will run after the other commands and +merge these modifications into the actual postinst scripts. + +In general, files named debian/*.debhelper and all content in +debian/.debhelper are internal to debhelper, and their existence or +use should not be relied on by external programs such as the build +process of a package. These files will be deleted by dh_clean. + +Debhelper programs should default to doing exactly what policy says to do. + +There are always exceptions. Just ask me. + +Introducing Dh_Lib: +------------------ + +Dh_Lib is the library used by all debhelper programs to parse their +arguments and set some useful variables. It's not mandatory that your +program use Dh_Lib.pm, but it will make it a lot easier to keep it in sync +with the rest of debhelper if it does, so this is highly encouraged. + +Use Dh_Lib like this: + +use Debian::Debhelper::Dh_Lib; +our $VERSION = '1.0'; +init(); + +The init() function causes Dh_lib to parse the command line and do +some other initialization tasks. If present, $main::VERSION will be +used to determine the version of the tool (e.g. embedded into +autoscript snippets). + +Argument processing: +------------------- + +All debhelper programs should respond to certain arguments, such as -v, -i, +-a, and -p. To help you make this work right, Dh_Lib.pm handles argument +processing. Just call init(). + +You can add support for additional options to your command by passing an +options hash to init(). The hash is then passed on the Getopt::Long to +parse the command line options. For example, to add a --foo option, which +sets $dh{FOO}: + +init(options => { foo => \$dh{FOO} }); + +After argument processing, some global variables are used to hold the +results; programs can use them later. These variables are elements of the +%dh hash. + +switch variable description +-v VERBOSE should the program verbosely output what it is + doing? +--no-act NO_ACT should the program not actually do anything? +-i,-a,-p,-N DOPACKAGES a space delimited list of the binary packages + to act on (in Dh_Lib.pm, this is an array) +-i DOINDEP set if we're acting on binary independent + packages +-a DOARCH set if we're acting on binary dependent + packages +-n NOSCRIPTS if set, do not make any modifications to the + package's postinst, postrm, etc scripts. +-o ONLYSCRIPTS if set, only make modifications to the + package's scripts, but don't look for or + install associated files. +-X EXCLUDE exclude a something from processing (you + decide what this means for your program) + (This is an array) +-X EXCLUDE_FIND same as EXCLUDE, except all items are put + into a string in a way that they will make + find find them. (Use ! in front to negate + that, of course) Note that this should + only be used inside complex_doit(), not in + doit(). +-d D_FLAG you decide what this means to your program +-P TMPDIR package build directory (implies only one + package is being acted on) +-u U_PARAMS will be set to a string, that is typically + parameters your program passes on to some + other program. (This is an array) +-V V_FLAG will be set to a string, you decide what it + means to your program +-V V_FLAG_SET will be 1 if -V was specified, even if no + parameters were passed along with the -V +-A PARAMS_ALL generally means that additional command line + parameters passed to the program (other than + those processed here), will apply to all + binary packages the program acts on, not just + the first +--mainpackage MAINPACKAGE controls which package is treated as the + main package to act on +--name NAME a name to use for installed files, instead of + the package name +--error-handler ERROR_HANDLER a function to call on error + +Any additional command line parameters that do not start with "-" will be +ignored, and you can access them later just as you normally would. + +Global variables: +---------------- + +The following keys are also set in the %dh hash when you call init(): + +MAINPACKAGE the name of the first binary package listed in + debian/control +FIRSTPACKAGE the first package we were instructed to act on. This package + typically gets special treatment; additional arguments + specified on the command line may effect it. + +Functions: +--------- + +Dh_Lib.pm also contains a number of functions you may find useful. + +doit([$options, ]@command) + Pass this function an array that is a command with arguments. + It will run the command (unless $dh{NO_ACT} is set), and + if $dh{VERBOSE} is set, it will also output the command to stdout. You + should use this function for almost all commands your program performs + that manipulate files in the package build directories. + + The $options argument (if passed) must be a hashref (added in debhelper 10.7). + The following key-value pairs can be used: + * stdout => A file name. The child process will have its STDOUT redirected + to that file. [debhelper (>= 10.7)] + * chdir => A directory. The child process will do a chdir into that + directory before executing the command. [debhelper (>= 10.9)] + * update_env => A hashref. Each key in it represents an environment variable + that should be set in the child (possibly replacing the existing value) + prior to the exec. If the value is undef, the environment variable will + be unset. Environment variables in %ENV but not listed in the update_env + hashref will be preserved as-is. [debhelper (>= 11.1)] + + This will *not* invoke a shell, so meta characters will not have any special + meaning. Use complex_doit for that (or emulate via "bash -c"). + NB: In compat 11 and below, there was a bug that would make doit fork a shell + in one special case. This is deprecated and will be removed in compat 12. + The detection code for this can be disabled by passing an empty hashref for + as $options. This will make doit unconditionally avoid forking a shell. +print_and_doit([$options, ]@command) + Like doit but will print unless $dh{QUIET} is set. See "Standardization" + above for when this is allowed to be called. +complex_doit($command) + Pass this function a string that is a shell command, it will run it + similarly to how doit() does. You can pass more complicated commands + to this (i.e. commands involving piping redirection), however, you + have to worry about things like escaping shell metacharacters. +verbose_print($message) + Pass this command a string, and it will echo it if $dh{VERBOSE} is set. +nonquiet_print($message) + Pass this command a string, and it will echo it unless $dh{QUIET} is set. + See "Standardization" above for when this is allowed to be called. +error($errormsg) + Pass this command a string, it will output it to standard error and + exit. +error_exitcode($cmd) + Pass this subroutine a string (representing a command line), it will + output a message describing that the command failed to standard error + and exit. Note that this relies on the value of $? to produce a + meaningful error message. Even if $? is 0, this /will/ still terminate + the program (although with a rather unhelpful message). +warning($message) + Pass this command a string, and it will output it to standard error + as a warning message. +tmpdir($dir) + Pass this command the name of a binary package, it will return the + name of the tmp directory that will be used as this package's + package build directory. Typically, this will be "debian/package". +compat($num) + Pass this command a number, and if the current compatibility level + is less than or equal to that number, it will return true. + Looks at DH_COMPAT to get the compatibility level. +pkgfile($package, $basename) + Pass this command the name of a binary package, and the base name of a + file, and it will return the actual filename to use. This is used + for allowing debhelper programs to have configuration files in the + debian/ directory, so there can be one config file per binary + package. The convention is that the files are named + debian/package.filename, and debian/filename is also allowable for + the $dh{MAINPACKAGE}. If the file does not exist, nothing is returned. + + If the *entire* behavior of a command, when run without any special + options, is determined by the existence of 1 or more pkgfiles, + or by the existence of a file or directory in a location in the + tmpdir, it can be marked as such, which allows dh to automatically + skip running it. Please see "Optimization techniques" below. + +pkgext($package) + Pass this command the name of a binary package, and it will return + the name to prefix to files in debian/ for this package. For the + $dh{MAINPACKAGE}, it returns nothing (there is no prefix), for the other + packages, it returns "package.". +isnative($package) + Pass this command the name of a package, it returns 1 if the package + is a native debian package. + As a side effect, $dh{VERSION} is set to the version number of the + package. +autoscript($package, $scriptname, $snippetname, $substparam) + Pass parameters: + - binary package to be affected + - script to add to + - filename of snippet. For testing purposes, you can set the + environment variable DH_DATAFILES containing a autoscripts + directory, which can be used to shadow the snippets provided + in /usr/share/debhelper/autoscripts (or to test newly added + snippets). + Older versions of debhelper (<< 13.1~) does not support + DH_DATAFILES. If you need to support debhelper (<< 13.1~) + then you can set DH_AUTOSCRIPTDIR to a directory containing + the snippets instead (note it should point to the autoscripts + directory unlike DH_DATAFILES). + - (optional) A substitution parameter, which is one of 3 types: + * sed commands to run on the snippet. E.g. s/#PACKAGE#/$PACKAGE/ + Note: Passed to the shell inside double quotes. + * a perl sub to invoke with $_ set to each line of the snippet + in turn. + * a hashref, where each key will substitute "#${key}#" with the + value that $key points to. [debhelper (>= 10.7)] + This command automatically adds shell script snippets to a debian + maintainer script (like the postinst or prerm). + Note that in v6 mode and up, the snippets are added in reverse + order for the removal scripts. +autotrigger($package, $trigger_type, $trigger_target) + This command automatically adds a trigger to the package. The + parameters: + - binary package to be affected + - the type of trigger (e.g. "activate-noawait") + - the target (e.g. "ldconfig" or "/usr/share/foo") +dirname($pathname) + Return directory part of pathname. +basename($pathname) + Return base of pathname, +addsubstvar($package, $substvar, $deppackage, $verinfo, $remove) + This function adds a dependency on some package to the specified + substvar in a package's substvar's file. It needs all these + parameters: + - binary package that gets the item + - name of the substvar to add the item to + - the package that will be depended on + - version info for the package (optional) (i.e. ">= 1.1") + - if this last parameter is passed, the thing that would be added + is removed instead. This can be useful to ensure that a debhelper + command is idempotent. (However, we generally don't bother, + and rely on the user calling dh_prep.) Note that without this + parameter, if you call the function twice with the same values it + will only add one item to the substvars file. +delsubstvar($package, $substvar) + This function removes the entire line for the substvar from the + package's shlibs file. +excludefile($filename) + This function returns true if -X has been used to ask for the file + to be excluded. +is_udeb($package) + Returns true if the package is marked as a udeb in the control + file. +getpackages($type) + Returns a list of packages in the control file. + Pass "arch" or "indep" to specify arch-dependent or + -independent. If $type is omitted, returns all + packages (including packages that are not built + for this architecture). Pass "both" to get the union + of "arch" and "indep" packages. + Note that "both" is *not* the same omitting the $type parameter. + As a side effect, populates %package_arches and %package_types with + the types of all packages (not only those returned). +get_source_date_epoch() + Return the value of $ENV{SOURCE_DATE_EPOCH} if exists. + Otherwise compute the value from the first changelog entry, + use it to set the ENV variable and return it. +inhibit_log() + Prevent logging the program's successful finish to + debian/*debhelper.log + + Since debhelper/12.9, this can be done by passing the inhibit_log + option with a value of 1 to init() instead. E.g. + init('inhibit_log' => 1); +load_log($package, $hashref) + Loads the log file for the given package and returns a list of + logged commands. + (Passing a hashref also causes it to populate the hash.) +write_log($cmd, $package ...) + Writes the log files for the specified package(s), adding + the cmd to the end. +restore_file_on_clean($file) + Store a copy of $file, which will be restored by dh_clean. + The $file *must* be a relative path to the package root and + *must* be a real regular file. Dirs, devices and symlinks + (and everything else) *cannot* be restored by this. + If $file is passed multiple times (e.g. from different programs) + only the first version is stored. + CAVEAT: This *cannot* undo arbitrary "rm -fr"'ing. The dir, + which is/was in $file, must be present when dh_clean is called. +make_symlink($src, $dest, $tmp) + Creates a Policy compliant system link called $dest pointing to + $src. If $tmp is given, then $tmp will be prefixed to $dest when + creating the actual symlink. +install_dh_config_file($src, $dest[, $mode]) + Installs $src into $dest with $mode (defaults to 0644). If + compat is 9 (or later) and $src is executable, $src will be + executed instead and its output will be used to generate the + $dest file. +install_dir(@dirs) + Create the directories denoted by the paths in @dirs and all + parent entries as well (as needed). It uses mode 0755. + If a directory listed in @dirs already exists, the function + silently skips that directory (similar to mkdir -p). +install_file($src, $dest) + Installs $src into $dest with mode 0644. The parent dir of + $dest must exist (can be created with install_dir). + This is intended for installing regular non-executable files. +install_prog($src, $dest) + Installs $src into $dest with mode 0755. The parent dir of + $dest must exist (can be created with install_dir). + This is intended for installing scripts or binaries. +install_lib($src, $dest) + Installs a library at the path $src into $dest. The parent + dir of $dest must exist (can be created with install_dir). + This is intended for installing libraries. +reset_perm_and_owner($mode, $path...) + Resets the ownership and mode (POSIX permissions) of $path + This is useful for files created directly by the script, but + it not necessary for files installed via the install_* + functions. + The file owner and group is set to "root:root". The change + is only done on the exact paths listed (i.e. it is *not* + recursive). + Mode should be passed as an integer (not a string). +open_gz($file) + Open $file, read from it as a gzip-compressed file and return + the file handle. + Depending on runtime features, it might be a pipe from an + external process (which will die with a "SIGPIPE" if you + do not consume all the input) +deprecated_functionality($warn_msg[, $rm_compat[, $rm_msg]]) + Emit $warn_msg as a deprecation warning, or error out if $rm_compat + is provided and equal to (or greater than) the active compat level. + The $rm_msg parameter can be used to provide a custom error message + in the latter case (if omitted, $warn_msg will be used in both cases). + The function will provide a separate diagnostic about which compat + level that will remove/removed the functionality if $rm_compat is + given. +log_installed_files($package, @paths) + Creates a logfile (in debian/.debhelper/generated) for the helper's + processing of $package, which installed the files listed in + @paths. This logfile will later be used by the dh_missing helper. + Paths should be relative to the package root (i.e. the directory + containing "debian/") and should not have superfluous segments + (e.g. avoid "foo/../bar" or "foo/./bar") + If a directory is listed, it and all paths recursively beneath is + also considered installed. +on_pkgs_in_parallel($code) - prototype: (&) + Short hand for on_items_in_parallel with $dh{DOPACKAGES} as + as list of packages. +on_items_in_parallel($item_list_ref, $code) + Splits all the items in $item_list_ref into a number of groups + based on the max parallel (as decided by DEB_BUILD_OPTIONS) + A subprocess is forked for each group (minimum 1 process will be + forked) and each subprocess will be given a group of items + to process. Each group is passed to the $code sub, which will + then process it and return normally on success. + Example: + my @all_packages = getpackages(); + on_items_in_parallel(\@all_packages, sub { + for my $package (@_) { + my $tmp=tmpdir($package); + my $pkgfile = pkgfile($package, 'foo'); + ...; + } + }); + my @work_list = compute_work_list(); + on_items_in_parallel(\@work_list, sub { + for my $item (@_) { + ...; + } + }); + + If there is an error, which should stop the build, please invoke + either "error()" or "error_exitcode". Alternatively, a trappable + error (e.g. "die($msg)") can also be used. + + Keep in mind that the sub will always be run in a subprocess, + so it cannot update global state. + +Sequence Addons: +--------------- + +The dh(1) command has a --with <addon> parameter that can be used to load +a sequence addon module named Debian::Debhelper::Sequence::<addon>. +These modules can add/remove commands to the dh command sequences, by +calling some functions from Dh_Lib: + +insert_before($existing_command, $new_command) + Insert $new_command in sequences before $existing_command + + Compatible with "arch-only"/"indep-only" modes if the command + appears only in a compatible sequence. + +insert_after($existing_command, $new_command) + Insert $new_command in sequences after $existing_command + + Compatible with "arch-only"/"indep-only" modes if the command + appears only in a compatible sequence. + +remove_command($existing_command) + Remove $existing_command from the list of commands to run + in all sequences. + + Cannot be used in "arch-only"/"indep-only" mode. + +add_command($new_command, $sequence) + Add $new_command to the beginning of the specified sequence. + If the sequence does not exist, it will be created. + + Compatible with "arch-only"/"indep-only" modes if $sequence + is an "-arch" or "-indep" sequence (respectively). + +add_command_options($command, $opt1, $opt2, ...) + Append $opt1, $opt2 etc. to the list of additional options which + dh passes when running the specified $command. These options are + not relayed to debhelper commands called via $command override. + + Cannot be used in "arch-only"/"indep-only" mode. + +remove_command_options($command) + Clear all additional $command options previously added with + add_command_options(). + + Cannot be used in "arch-only"/"indep-only" mode. + +remove_command_options($command, $opt1, $opt2, ...) + Remove $opt1, $opt2 etc. from the list of additional options which + dh passes when running the specified $command. + + Cannot be used in "arch-only"/"indep-only" mode. + +declare_command_obsolete($command) + Declare $command as obsolete, which make dh warn about leftover + override / hook targets. Note that $command MUST NOT be present + in the sequence! + + Cannot be used in "arch-only"/"indep-only" mode. + + +Optimization techniques: +------------------------ + +Most debhelper tools will have situations where they are not useful and can +be skipped. To support this, dh will look for a "NOOP PROMISE" as a part of +a comment in the command before running it. These promises have the form: + + # PROMISE: DH NOOP WITHOUT pkgfile-logged(pkgfileA) pkgfile-logged(pkgfileB) tmp(need/this) cli-options() + +The following keywords are defined: + + * pkgfile(X): The command might do something if debian/X (or debian/<package>.X) + exist for any of the packages it will be run for. If the debhelper tool + interacts with dh_missing, you always want to use pkgfile-logged(X) instead. + + * pkgfile-logged(X): Same as pkgfile(X) but it will also register which files + it handles so dh_missing can see it. + + * tmp(X): The command might do something if debian/<package>/X exists. + + * cli-options(--foo|--bar): The command might do something if *either* --foo + OR --bar are passed to the command. + + * cli-options(BUILDSYSTEM): The command is a build system command (dh_auto_*) + and will react to standard build system command line options. + + * cli-options(): Special variant of cli-options() to declare that command line + options will not affect whether the tool will do something. This enables + dh to skip commands even when passed custom options. Without an explicit + cli-option(...) hint, dh will assume the command might react to it. + +If the hint is present and ALL of the keywords imply that the command can be +skipped, dh will skip the command. + +Logging helpers and dh_missing: +------------------------------- + +Since debhelper 10.3, debhelper has had a helper called "dh_missing". It +takes over the "--list-missing" and "--fail-missing" options from dh_install +and as the advantage that it can "see" what other helpers have installed. + +Under the hood, this works by the helpers logging the source files +they (would) install to a hidden log file. When dh_missing is called, +it reads all these log files to determine which files have would been +installed and compare them to what is present. + +If you are writing a helper that need to integrate with dh_missing, +here is what you do: + +Dh_Lib-based helpers: +~~~~~~~~~~~~~~~~~~~~~ + + * Replace "@{$dh{DOPACKAGES}}" with "getpackages()" and use + "process_pkg($package)" to determine if the helper should actually + install anything. + * Call "log_installed_files" at least once per package (even on the ones + that are not to be acted on) with a list of source files that would be + installed. + - You can list entire directories even if there are files under + it that are ignored. + - Please call "log_installed_files" /even if/ the list is empty for that + packages. This enables dh_missing to see that the helper has been run + and nothing should be installed for that package. + - Prefer calling "log_installed_files" /exactly once/ per package as + this is what it is optimized for. + * If your helper has a PROMISE, it must use "pkgfile-logged(<file>)" + for its config files. (See #867246) + - CAVEAT: This requires a dependency on "debhelper (>= 10.2.5)". Prior + to that version, debhelper will wrongly optimize your helper out. + * Consider using dh_installman or dh_installexamples as examples. + +Other helpers: +~~~~~~~~~~~~~~ + + * The helper must compile a list of files it would have installed for + each package (even packages that are not acted on). The file list + should be relative to the source package root (e.g. + "debian/tmp/usr/bin/bar"). + - This list can also contain directories. They will be flagged as + installed along with their content (recursively). + * The helper must append to the file (create it if missing): + debian/.debhelper/generated/${package}/installed-by-${HELPER_NAME} + - Example: debian/.debhelper/generated/lintian/installed-by-dh_install + - The file should be created even if it is empty. This enables dh_missing + to see that the helper has been run and nothing would be installed for + that package. + * Please append to the file if it exists as the helper may be called multiple + times (once with -a and once with -i). It is completely fine if this leaves + duplicate entries as dh_missing will deduplicate these. + * If your helper has a PROMISE, it must use "pkgfile-logged(<file>)" + for its config files. (See #867246) + - CAVEAT: This requires a dependency on "debhelper (>= 10.2.5)". Prior + to that version, debhelper will wrongly optimize your helper out. + +Buildsystem Classes: +-------------------- + +The dh_auto_* commands are frontends that use debhelper buildsystem +classes. These classes have names like Debian::Debhelper::Buildsystem::foo, +and are derived from Debian::Debhelper::Buildsystem, or other, related +classes. + +A buildsystem class needs to inherit or define these methods: DESCRIPTION, +check_auto_buildable, configure, build, test, install, clean. See the comments +inside Debian::Debhelper::Buildsystem for details. Note that this interface +is still subject to change. + +Note that third-party buildsystems will not automatically be used by +default. The package maintainer will either have to explicitly enable +it via the --buildsystem parameter OR the build system should be +registered in debhelper. The latter is currently needed to ensure a +stable and well-defined ordering of the build systems. + +-- Joey Hess <joeyh@debian.org> |