Re: [PATCH v7 1/2] grep: refactor next_match() and match_one_pattern() for external use
From: Junio C Hamano <hidden>
Date: 2021-09-23 17:25:34
Hamza Mahfooz [off-list ref] writes:
quoted hunk
These changes are made in preparation of, the colorization support for the "git log" subcommands that, rely on regex functionality (i.e. "--author", "--committer" and "--grep"). These changes are necessary primarily because match_one_pattern() expects header lines to be prefixed, however, in pretty, the prefixes are stripped from the lines because the name-email pairs needs to go through additional parsing, before they can be printed and because next_match() doesn't handle the case of "ctx == GREP_CONTEXT_HEAD" at all. So, teach next_match() how to handle the new case, move header_field[] so it can be used by pretty to reappend relevant prefixes and teach match_one_pattern() how to handle subsequent header line match attempts. Signed-off-by: Hamza Mahfooz <redacted> --- v5: separate grep changes from pretty changes. v6: rescope some variables. v7: export header_field[] and allow for subsequent matches on header lines in match_one_pattern(). --- grep.c | 53 ++++++++++++++++++++++++++++------------------------- grep.h | 13 +++++++++++++ 2 files changed, 41 insertions(+), 25 deletions(-)diff --git a/grep.c b/grep.c index 14fe8a0fd2..f4126011c5 100644 --- a/grep.c +++ b/grep.c@@ -935,15 +935,6 @@ static void strip_timestamp(const char *bol, const char **eol_p) } } -static struct { - const char *field; - size_t len; -} header_field[] = { - { "author ", 7 }, - { "committer ", 10 }, - { "reflog ", 7 }, -}; - static int match_one_pattern(struct grep_pat *p, const char *bol, const char *eol, enum grep_context ctx,@@ -953,18 +944,23 @@ static int match_one_pattern(struct grep_pat *p, const char *start = bol; if ((p->token != GREP_PATTERN) && - ((p->token == GREP_PATTERN_HEAD) != (ctx == GREP_CONTEXT_HEAD))) + ((p->token == GREP_PATTERN_HEAD) != (ctx == GREP_CONTEXT_HEAD)) && + ((p->token == GREP_PATTERN_BODY) != (ctx == GREP_CONTEXT_BODY))) return 0; if (p->token == GREP_PATTERN_HEAD) { - const char *field; - size_t len; - assert(p->field < ARRAY_SIZE(header_field)); - field = header_field[p->field].field; - len = header_field[p->field].len; - if (strncmp(bol, field, len)) - return 0; - bol += len; + if (!(eflags & REG_NOTBOL)) { + const char *field; + size_t len; + + assert(p->field < ARRAY_SIZE(grep_header_fields)); + field = grep_header_fields[p->field].field; + len = grep_header_fields[p->field].len; + if (strncmp(bol, field, len)) + return 0; + bol += len; + } + switch (p->field) { case GREP_HEADER_AUTHOR: case GREP_HEADER_COMMITTER:saved_ch = strip_timestamp(bol, &eol);
Let's first see if we correctly understand how the original was designed to be used. It is called once per line, with "bol" set to the true beginning of the line. For a line in the header (e.g. "author A U Thor [off-list ref] 12345678 +0000"), therefore, we ensure we are looking at the right type of the header (e.g. when looking for an "author" line, the line must begin with "author "), or we return 0 (i.e. does not match). And then, for "author" and "committer" line, we adjust the eol to exclude the timestamp part from pattern the matching by calling strip_timetamp(). Both of these special case used to be unconditional because we _knew_ that the caller would call this function with "bol" pointing at the true beginning of the line. The patch adds a new !(eflags & REG_NOTBOL) guard, presumably because new callers will start calling this function with "bol" set to point in the middle of a line? So we only do the "check the kind of header and skip a line that records the commiter when we are looking for an author" part when the guard passes, i.e. we know that the caller called us with the true beginning of the line in bol. But how would the new caller that points "bol" at middle of a line make sure that we are looking at the right kind of header? If the pattern p is set to match only for an author line, the first call with "bol" set to the true beginning of the line will correctly reject a "committer" header, but because you lost the sanity check above, the second and subsequent one will go ahead and scan for the pattern p on the line, even if p->field asks for author line and the line records the committer. You'd end up finding a commit object that is committed by (but not authored by) the person when you are looking for a commit that was authored by somebody, no? If you ask for commits by somebody (e.g. "--author=Hazma") with an output format that shows both the author and the committer (e.g. "log --pretty=fuller"), wouldn't your "hit coloring" code show Hazma on the committer name as a grep hit, too? Also, because the function is designed to be called with bol and eol set to true beginning and the end of the line, the strip_timestamp() side of the logic should also be done only once, but that is not what is happening in the patch. Chomping the line immediately after the last occurrence of '>' is idempotent, so it is OK to have the logic outside the new !(eflags & REG_NOTBOL) guard, but discarding the updated eol from the first call and not reusing the result of the strip_timestamp() in the second and subsequent call smells like a waste. I am having a feeling that you'd need to make the caller of this function (either the direct callers, or you may want to introduce another layer between the current direct callers and this function) perform these massaging for the prefix and trailing parts of the line for GREP_PATTERN_HEAD patterns, so that this function, if you were to change it to be callable many times starting at a middle of the line, only needs to care about matching the pattern in the portion between (bol, eol) and nothing else.