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grep: teach --debug option to dump the parse tree
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Our "grep" allows complex boolean expressions to be formed to match
each individual line with operators like --and, '(', ')' and --not.
Introduce the "--debug" option to show the parse tree to help people
who want to debug and enhance it.

Also "log" learns "--grep-debug" option to do the same.  The command
line parser to the log family is a lot more limited than the general
"git grep" parser, but it has special handling for header matching
(e.g. "--author"), and a parse tree is valuable when working on it.

Note that "--all-match" is *not* any individual node in the parse
tree.  It is an instruction to the evaluator to check all the nodes
in the top-level backbone have matched and reject a document as
non-matching otherwise.

Signed-off-by: Junio C Hamano <gitster@pobox.com>
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Junio C Hamano committed Sep 14, 2012
1 parent 785ee49 commit 17bf35a
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Showing 4 changed files with 96 additions and 2 deletions.
3 changes: 3 additions & 0 deletions builtin/grep.c
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Original file line number Diff line number Diff line change
Expand Up @@ -772,6 +772,9 @@ int cmd_grep(int argc, const char **argv, const char *prefix)
"indicate hit with exit status without output"),
OPT_BOOLEAN(0, "all-match", &opt.all_match,
"show only matches from files that match all patterns"),
{ OPTION_SET_INT, 0, "debug", &opt.debug, NULL,
"show parse tree for grep expression",
PARSE_OPT_NOARG | PARSE_OPT_HIDDEN, NULL, 1 },
OPT_GROUP(""),
{ OPTION_STRING, 'O', "open-files-in-pager", &show_in_pager,
"pager", "show matching files in the pager",
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92 changes: 90 additions & 2 deletions grep.c
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Original file line number Diff line number Diff line change
Expand Up @@ -332,6 +332,87 @@ static struct grep_expr *compile_pattern_expr(struct grep_pat **list)
return compile_pattern_or(list);
}

static void indent(int in)
{
while (in-- > 0)
fputc(' ', stderr);
}

static void dump_grep_pat(struct grep_pat *p)
{
switch (p->token) {
case GREP_AND: fprintf(stderr, "*and*"); break;
case GREP_OPEN_PAREN: fprintf(stderr, "*(*"); break;
case GREP_CLOSE_PAREN: fprintf(stderr, "*)*"); break;
case GREP_NOT: fprintf(stderr, "*not*"); break;
case GREP_OR: fprintf(stderr, "*or*"); break;

case GREP_PATTERN: fprintf(stderr, "pattern"); break;
case GREP_PATTERN_HEAD: fprintf(stderr, "pattern_head"); break;
case GREP_PATTERN_BODY: fprintf(stderr, "pattern_body"); break;
}

switch (p->token) {
default: break;
case GREP_PATTERN_HEAD:
fprintf(stderr, "<head %d>", p->field); break;
case GREP_PATTERN_BODY:
fprintf(stderr, "<body>"); break;
}
switch (p->token) {
default: break;
case GREP_PATTERN_HEAD:
case GREP_PATTERN_BODY:
case GREP_PATTERN:
fprintf(stderr, "%.*s", (int)p->patternlen, p->pattern);
break;
}
fputc('\n', stderr);
}

static void dump_grep_expression_1(struct grep_expr *x, int in)
{
indent(in);
switch (x->node) {
case GREP_NODE_TRUE:
fprintf(stderr, "true\n");
break;
case GREP_NODE_ATOM:
dump_grep_pat(x->u.atom);
break;
case GREP_NODE_NOT:
fprintf(stderr, "(not\n");
dump_grep_expression_1(x->u.unary, in+1);
indent(in);
fprintf(stderr, ")\n");
break;
case GREP_NODE_AND:
fprintf(stderr, "(and\n");
dump_grep_expression_1(x->u.binary.left, in+1);
dump_grep_expression_1(x->u.binary.right, in+1);
indent(in);
fprintf(stderr, ")\n");
break;
case GREP_NODE_OR:
fprintf(stderr, "(or\n");
dump_grep_expression_1(x->u.binary.left, in+1);
dump_grep_expression_1(x->u.binary.right, in+1);
indent(in);
fprintf(stderr, ")\n");
break;
}
}

void dump_grep_expression(struct grep_opt *opt)
{
struct grep_expr *x = opt->pattern_expression;

if (opt->all_match)
fprintf(stderr, "[all-match]\n");
dump_grep_expression_1(x, 0);
fflush(NULL);
}

static struct grep_expr *grep_true_expr(void)
{
struct grep_expr *z = xcalloc(1, sizeof(*z));
Expand Down Expand Up @@ -395,7 +476,7 @@ static struct grep_expr *prep_header_patterns(struct grep_opt *opt)
return header_expr;
}

void compile_grep_patterns(struct grep_opt *opt)
static void compile_grep_patterns_real(struct grep_opt *opt)
{
struct grep_pat *p;
struct grep_expr *header_expr = prep_header_patterns(opt);
Expand All @@ -415,7 +496,7 @@ void compile_grep_patterns(struct grep_opt *opt)

if (opt->all_match || header_expr)
opt->extended = 1;
else if (!opt->extended)
else if (!opt->extended && !opt->debug)
return;

p = opt->pattern_list;
Expand All @@ -435,6 +516,13 @@ void compile_grep_patterns(struct grep_opt *opt)
opt->all_match = 1;
}

void compile_grep_patterns(struct grep_opt *opt)
{
compile_grep_patterns_real(opt);
if (opt->debug)
dump_grep_expression(opt);
}

static void free_pattern_expr(struct grep_expr *x)
{
switch (x->node) {
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1 change: 1 addition & 0 deletions grep.h
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Original file line number Diff line number Diff line change
Expand Up @@ -90,6 +90,7 @@ struct grep_opt {
int word_regexp;
int fixed;
int all_match;
int debug;
#define GREP_BINARY_DEFAULT 0
#define GREP_BINARY_NOMATCH 1
#define GREP_BINARY_TEXT 2
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2 changes: 2 additions & 0 deletions revision.c
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Original file line number Diff line number Diff line change
Expand Up @@ -1578,6 +1578,8 @@ static int handle_revision_opt(struct rev_info *revs, int argc, const char **arg
} else if ((argcount = parse_long_opt("grep", argv, &optarg))) {
add_message_grep(revs, optarg);
return argcount;
} else if (!strcmp(arg, "--grep-debug")) {
revs->grep_filter.debug = 1;
} else if (!strcmp(arg, "--extended-regexp") || !strcmp(arg, "-E")) {
revs->grep_filter.regflags |= REG_EXTENDED;
} else if (!strcmp(arg, "--regexp-ignore-case") || !strcmp(arg, "-i")) {
Expand Down

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