commands: new method for defining commands

. Define a prototype for every lvm command.
. Match every user command with one definition.
. Generate help text and man pages from them.

The new file command-lines.in defines a prototype for every
unique lvm command.  A unique lvm command is a unique
combination of: command name + required option args +
required positional args.  Each of these prototypes also
includes the optional option args and optional positional
args that the command will accept, a description, and a
unique string ID for the definition.  Any valid command
will match one of the prototypes.

Here's an example of the lvresize command definitions from
command-lines.in, there are three unique lvresize commands:

lvresize --size SizeMB LV
OO: --alloc Alloc, --autobackup Bool, --force,
--nofsck, --nosync, --noudevsync, --reportformat String, --resizefs,
--stripes Number, --stripesize SizeKB, --poolmetadatasize SizeMB
OP: PV ...
ID: lvresize_by_size
DESC: Resize an LV by a specified size.

lvresize LV PV ...
OO: --alloc Alloc, --autobackup Bool, --force,
--nofsck, --nosync, --noudevsync,
--reportformat String, --resizefs, --stripes Number, --stripesize SizeKB
ID: lvresize_by_pv
DESC: Resize an LV by specified PV extents.
FLAGS: SECONDARY_SYNTAX

lvresize --poolmetadatasize SizeMB LV_thinpool
OO: --alloc Alloc, --autobackup Bool, --force,
--nofsck, --nosync, --noudevsync,
--reportformat String, --stripes Number, --stripesize SizeKB
OP: PV ...
ID: lvresize_pool_metadata_by_size
DESC: Resize a pool metadata SubLV by a specified size.

The three commands have separate definitions because they have
different required parameters.  Required parameters are specified
on the first line of the definition.  Optional options are
listed after OO, and optional positional args are listed after OP.

This data is used to generate corresponding command definition
structures for lvm in command-lines.h.  usage/help output is also
auto generated, so it is always in sync with the definitions.

Every user-entered command is compared against the set of
command structures, and matched with one.  An error is
reported if an entered command does not have the required
parameters for any definition.  The closest match is printed
as a suggestion, and running lvresize --help will display
the usage for each possible lvresize command.

The prototype syntax used for help/man output includes
required --option and positional args on the first line,
and optional --option and positional args enclosed in [ ]
on subsequent lines.

  command_name <required_opt_args> <required_pos_args>
          [ <optional_opt_args> ]
          [ <optional_pos_args> ]

Command definitions that are not to be advertised/suggested
have the flag SECONDARY_SYNTAX.  These commands will not be
printed in the normal help output.

Man page prototypes are also generated from the same original
command definitions, and are always in sync with the code
and help text.

Very early in command execution, a matching command definition
is found.  lvm then knows the operation being done, and that
the provided args conform to the definition.  This will allow
lots of ad hoc checking/validation to be removed throughout
the code.

Each command definition can also be routed to a specific
function to implement it.  The function is associated with
an enum value for the command definition (generated from
the ID string.)  These per-command-definition implementation
functions have not yet been created, so all commands
currently fall back to the existing per-command-name
implementation functions.

Using per-command-definition functions will allow lots of
code to be removed which tries to figure out what the
command is meant to do.  This is currently based on ad hoc
and complicated option analysis.  When using the new
functions, what the command is doing is already known
from the associated command definition.

1 files changed, 136 insertions, 0 deletions

diff --git a/tools/vals.h b/tools/vals.h
new file mode 100644
index 000000000..c8c998fac
--- /dev/null
+++ b/tools/vals.h
@@ -0,0 +1,136 @@
+
+/*
+ * Define value types which describe values accepted
+ * by the --option's in args.h, and can also describe
+ * the values accepted as positional args.
+ *
+ * Previously, accepted values were only "described"
+ * by identifying the parsing function to use.
+ *
+ * Some standard val types are used by many options,
+ * e.g. many options (aa_ARG, bb_ARG, cc_ARG) all
+ * accept a number_VAL.
+ *
+ * Other special val types are used by only one option,
+ * e.g. only mirrorlog_ARG accepts a mirrorlog_VAL.
+ * This typically means that there are some specific
+ * words that are recognized after the option.
+ *
+ * Some options currently take a standard val type,
+ * (esp string_VAL), but they could be given their
+ * own custom val type.  The advantage of using a
+ * custom val type is the possibility of validating
+ * the value when parsing it with a custom parsing
+ * function, and the possibility of displaying the
+ * actual accepted values in the command usage.
+ * Without a custom val type, the code must do ad hoc
+ * validation of the string values, and the usage
+ * output for the option will only say "String"
+ * rather than giving the accepted string values.
+ * Even without a custom parsing function, there is
+ * reason to define a custom x_VAL enum so that a
+ * more descriptive usage string can be specified
+ * as opposed to just "String".
+ *
+ * Most of the val types defined here are used after
+ * --option's, and are referenced in foo_ARG entries
+ * in args.h.  But, some val types are only used to
+ * represent positional values in command definitions,
+ * e.g. vg_VAL.
+ *
+ * val(a, b, c, d)
+ *
+ * a:  foo_VAL enums
+ * b:  the function to parse and set the value
+ * c:  the name used to reference this value in command defs
+ * d:  what to display in usage output for this value
+ *
+ * command defintions will use --option NAME, where NAME
+ * is shown in val() field c.  NAME will be translated to
+ * foo_VAL enum in field a, which is used in commands[]
+ * structs.
+ *
+ * option definitions (arg.h) will reference foo_VAL enum
+ * in field a.
+ *
+ * FIXME: for specialized val types, the set of recognized
+ * words is not defined or stored in a consistent way,
+ * but is just whatever the parsing function happens to look
+ * for, so adding a new accepted value for the val type is
+ * generally making the parsing function recognize a new
+ * word, and making the implementation code also recognize
+ * that word to do something different.  This new word should
+ * then also be added to the usage string for the val type here.
+ * It would be nice if the accepted values could be defined in a
+ * more consistent way, and perhaps in a single place, perhaps in
+ * struct val_props.
+ *
+ * The usage text for an option is not always the full
+ * set of words accepted for an option, but may be a
+ * subset.  i.e. an outdated word that no longer does
+ * anything may not be shown, but may still be recognized
+ * and ignored, or an option that shouldn't be used in
+ * general isn't shown to avoid suggesting it.
+ * e.g. for --activate we show the most common "y|n|ay"
+ * without showing the lvmlockd variations "ey|sy" which
+ * are not applicable in general.
+ *
+ * FIXME: are there some specialized or irrelevant
+ * options included in the usage text below that should
+ * be removed?  Should "lvm1" be removed?
+ *
+ * For Number args that take optional units, a full usage
+ * could be "Number[bBsSkKmMgGtTpPeE]" (with implied |),
+ * but repeating this full specification produces cluttered
+ * output, and doesn't indicate which unit is the default.
+ * "Number[units]" would be cleaner, as would a subset of
+ * common units, e.g. "Number[kmg...]", but neither helps
+ * with default.  "Number[k|unit]" and "Number[m|unit]" show
+ * the default, and "unit" indicates that other units
+ * are possible without listing them all.  This also
+ * suggests using the preferred lower case letters, because
+ * --size and other option args treat upper/lower letters
+ * the same, all as 1024 SI base.  For this reason, we
+ * should avoid suggesting the upper case letters.
+ */
+
+val(none_VAL, NULL, "None", "ERR")             /* unused, for enum value 0 */
+val(conststr_VAL, NULL, "ConstString", "ERR")  /* used only for command defs */
+val(constnum_VAL, NULL, "ConstNumber", "ERR")  /* used only for command defs */
+val(bool_VAL, yes_no_arg, "Bool", "y|n")
+val(number_VAL, int_arg, "Number", NULL)
+val(string_VAL, string_arg, "String", NULL)
+val(vg_VAL, string_arg, "VG", NULL)
+val(lv_VAL, string_arg, "LV", NULL)
+val(pv_VAL, string_arg, "PV", NULL)
+val(tag_VAL, tag_arg, "Tag", NULL)
+val(select_VAL, NULL, "Select", NULL)       /* used only for command defs */
+val(activationmode_VAL, string_arg, "ActivationMode", "partial|degraded|complete")
+val(activation_VAL, activation_arg, "Active", "y|n|ay")
+val(cachemode_VAL, cachemode_arg, "CacheMode", "writethrough|writeback")
+val(discards_VAL, discards_arg, "Discards", "passdown|nopassdown|ignore")
+val(mirrorlog_VAL, mirrorlog_arg, "MirrorLog", "core|disk")
+val(sizekb_VAL, size_kb_arg, "SizeKB", "Number[k|unit]")
+val(sizemb_VAL, size_mb_arg, "SizeMB", "Number[m|unit]")
+val(numsigned_VAL, int_arg_with_sign, "SNumber", "[+|-]Number")
+val(numsignedper_VAL, int_arg_with_sign_and_percent, "SNumberP", "[+|-]Number[%VG|%PVS|%FREE]")
+val(permission_VAL, permission_arg, "Permission", "rw|r")
+val(metadatatype_VAL, metadatatype_arg, "MetadataType", "lvm2|lvm1")
+val(units_VAL, string_arg, "Units", "hHbBsSkKmMgGtTpPeE")
+val(segtype_VAL, segtype_arg, "SegType", "linear|striped|snapshot|mirror|raid*|thin|cache|thin-pool|cache-pool")
+val(alloc_VAL, alloc_arg, "Alloc", "contiguous|cling|cling_by_tags|normal|anywhere|inherit")
+val(locktype_VAL, locktype_arg, "LockType", "sanlock|dlm|none")
+val(readahead_VAL, readahead_arg, "Readahead", "auto|none|NumberSectors")
+val(vgmetadatacopies_VAL, vgmetadatacopies_arg, "MetadataCopiesVG", "all|unmanaged|Number")
+val(pvmetadatacopies_VAL, pvmetadatacopies_arg, "MetadataCopiesPV", "0|1|2")
+val(metadatacopies_VAL, metadatacopies_arg, "unused", "unused")
+val(polloperation_VAL, polloperation_arg, "PollOp", "pvmove|convert|merge|merge_thin")
+val(writemostly_VAL, writemostly_arg, "WriteMostlyPV", "PV[:t|n|y]")
+val(syncaction_VAL, syncaction_arg, "SyncAction", "check|repair")
+val(reportformat_VAL, reportformat_arg, "ReportFmt", "basic|json")
+val(configreport_VAL, configreport_arg, "ConfigReport", "log|vg|lv|pv|pvseg|seg")
+val(configtype_VAL, configtype_arg, "ConfigType", "current|default|diff|full|list|missing|new|profilable|profilable-command|profilable-metadata")
+
+/* this should always be last */
+val(VAL_COUNT, NULL, NULL, NULL)
+