Re: [PATCH v6 7/7] grep: simplify config parsing and option parsing
- From
Junio C Hamano <gitster@pobox.com>
- Date
- Dec 27, 2021, 06:06 UTC
- Message-ID
- <xmqqpmpid1jc.fsf@gitster.g>
- In-Reply-To
- <patch-v6-7.7-88dfd40bf9e-20211226T223035Z-avarab@gmail.com>
Ævar Arnfjörð Bjarmason <avarab@gmail.com> writes:
Show 33 quoted lines
> @@ -143,7 +142,6 @@ struct grep_opt {
> int unmatch_name_only;
> int count;
> int word_regexp;
> - int fixed;
> int all_match;
> #define GREP_BINARY_DEFAULT 0
> #define GREP_BINARY_NOMATCH 1
> @@ -152,7 +150,6 @@ struct grep_opt {
> int allow_textconv;
> int extended;
> int use_reflog_filter;
> - int pcre2;
> int relative;
> int pathname;
> int null_following_name;
> @@ -162,7 +159,7 @@ struct grep_opt {
> int funcname;
> int funcbody;
> int extended_regexp_option;
> - int pattern_type_option;
> + enum grep_pattern_type pattern_type_option;
> int ignore_locale;
> char colors[NR_GREP_COLORS][COLOR_MAXLEN];
> unsigned pre_context;
> @@ -181,7 +178,6 @@ struct grep_opt {
> .relative = 1, \
> .pathname = 1, \
> .max_depth = -1, \
> - .pattern_type_option = GREP_PATTERN_TYPE_UNSPECIFIED, \
> .colors = { \
> [GREP_COLOR_CONTEXT] = "", \
> [GREP_COLOR_FILENAME] = "", \I very much like the lossage of redundant fixed and pcre2 members.
As I kept telling you, we still need a separate bit to keep track of the last value of grep.extendedRegexp, but the primary mechanism to determine what pattern type to use should be a single enum that is pattern_type. When we see "fixed", "pcre", "-G", etc. from grep.patternType config or from command line, we can stuff their enum values in pattern_type member of this struct, and when we see "default", we need to leave "default" in pattern_type member until we see the last definition of grep.extendedRegexp, at which time we can turn it into either "basic" or "extended".
So having only two members is absolutely the right thing to do.
But this part convinces me that whatever this patch does, it will not possible be capable of doing the right thing. You cannot implement "we have to remember that the last grep.patternType we saw was DEFAULT and in that case we cannot decide the real pattern type until we see the last definition of grep.extendedRegexp, which may be well after we saw the last grep.patternType definition" without a value in this enum to express that the last value we saw was DEFAULT.
Show 7 quoted lines
> enum grep_pattern_type {
> - GREP_PATTERN_TYPE_UNSPECIFIED = 0,
> - GREP_PATTERN_TYPE_BRE,
> + GREP_PATTERN_TYPE_BRE = 0,
> GREP_PATTERN_TYPE_ERE,
> GREP_PATTERN_TYPE_FIXED,
> GREP_PATTERN_TYPE_PCREShow 5 quoted lines
> @@ -982,7 +981,6 @@ int cmd_grep(int argc, const char **argv, const char *prefix) > argc = parse_options(argc, argv, prefix, options, grep_usage, > PARSE_OPT_KEEP_DASHDASH | > PARSE_OPT_STOP_AT_NON_OPTION); > - grep_commit_pattern_type(pattern_type_arg, &opt);
In other words, this lossage is likely wrong. Let's keep reading and see how well the config reader in this patch does.
Show 25 quoted lines
> @@ -61,11 +59,25 @@ int grep_config(const char *var, const char *value, void *cb)
> return -1;
>
> if (!strcmp(var, "grep.extendedregexp")) {
> + if (opt->extended_regexp_option == -1)
> + return 0;
> opt->extended_regexp_option = git_config_bool(var, value);
> + if (opt->extended_regexp_option)
> + opt->pattern_type_option = GREP_PATTERN_TYPE_ERE;
> + else
> + opt->pattern_type_option = GREP_PATTERN_TYPE_BRE;
> + return 0;
> + }
> + if (!strcmp(var, "grep.patterntype") &&
> + !strcmp(value, "default")) {
> + opt->pattern_type_option = opt->extended_regexp_option == 1
> + ? GREP_PATTERN_TYPE_ERE : GREP_PATTERN_TYPE_BRE;
> return 0;
> }
>
> if (!strcmp(var, "grep.patterntype")) {
> + opt->extended_regexp_option = -1; /* ignore */
> opt->pattern_type_option = parse_pattern_type_arg(var, value);
> return 0;
> }The above does not look correct at all.
What happens when the configuration parser sees these configuration variables in this sequence:
- grep.patternType set to say "pcre" (or anything not "default"). - grep.extendedRegexp set to "true". - grep.patternType set to "default".
After these three variable definitions with the usual "last one wins" (for each variable independently), the last value for the grep.patternType variable is "default", and the last value for the grep.extendedRegexp variable is "true". The user wants to use the ERE patterns.
The way the above code would work on this three variable definition sequence, as far as I read it, would however not give us the desired behaviour. First we drop extended_regexp_option member to -1 while setting PCRE to attern_type_option member, and then grep.extendedRegexp is totally ignored, and then we see patterntype set to default and notice extended_regexp_option is *NOT* 1 (because you ignored it and left it to -1), and end up using BRE, no?
I agree 100% with the direction that .fixed and .pcre2 members that were added over time to the struct are redundant and it is a very good idea to get rid of them. But we need to keep track of two configuration variables separately to allow them the "last one wins" semantics independently, and for that, you cannot lose the "default" value from the enum. It is impossible not to store the fact that "default" was the last value so far we saw for grep.patternType because you do not know, at the point of seeing "default", what the final value for grep.extendedRegexp will be. If you want to correctly implement the interaction between two variables without regression, that is.