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31 // Author: Dave Nicponski
33 // Bash-style command line flag completion for C++ binaries
35 // This module implements bash-style completions. It achieves this
36 // goal in the following broad chunks:
38 // 1) Take a to-be-completed word, and examine it for search hints
39 // 2) Identify all potentially matching flags
40 // 2a) If there are no matching flags, do nothing.
41 // 2b) If all matching flags share a common prefix longer than the
42 // completion word, output just that matching prefix
43 // 3) Categorize those flags to produce a rough ordering of relevence.
44 // 4) Potentially trim the set of flags returned to a smaller number
45 // that bash is happier with
46 // 5) Output the matching flags in groups ordered by relevence.
47 // 5a) Force bash to place most-relevent groups at the top of the list
48 // 5b) Trim most flag's descriptions to fit on a single terminal line
54 #include <string.h> // for strlen
61 #include <gflags/gflags.h>
67 #ifndef PATH_SEPARATOR
68 #define PATH_SEPARATOR '/'
71 DEFINE_string(tab_completion_word, "",
72 "If non-empty, HandleCommandLineCompletions() will hijack the "
73 "process and attempt to do bash-style command line flag "
74 "completion on this value.");
75 DEFINE_int32(tab_completion_columns, 80,
76 "Number of columns to use in output for tab completion");
78 _START_GOOGLE_NAMESPACE_
82 // Function prototypes and Type forward declarations. Code may be
83 // more easily understood if it is roughly ordered according to
84 // control flow, rather than by C's "declare before use" ordering
85 struct CompletionOptions;
88 // The entry point if flag completion is to be used.
89 static void PrintFlagCompletionInfo(void);
92 // 1) Examine search word
93 static void CanonicalizeCursorWordAndSearchOptions(
94 const string &cursor_word,
95 string *canonical_search_token,
96 CompletionOptions *options);
98 static bool RemoveTrailingChar(string *str, char c);
101 // 2) Find all matches
102 static void FindMatchingFlags(
103 const vector<CommandLineFlagInfo> &all_flags,
104 const CompletionOptions &options,
105 const string &match_token,
106 set<const CommandLineFlagInfo *> *all_matches,
107 string *longest_common_prefix);
109 static bool DoesSingleFlagMatch(
110 const CommandLineFlagInfo &flag,
111 const CompletionOptions &options,
112 const string &match_token);
115 // 3) Categorize matches
116 static void CategorizeAllMatchingFlags(
117 const set<const CommandLineFlagInfo *> &all_matches,
118 const string &search_token,
119 const string &module,
120 const string &package_dir,
121 NotableFlags *notable_flags);
123 static void TryFindModuleAndPackageDir(
124 const vector<CommandLineFlagInfo> all_flags,
126 string *package_dir);
129 // 4) Decide which flags to use
130 static void FinalizeCompletionOutput(
131 const set<const CommandLineFlagInfo *> &matching_flags,
132 CompletionOptions *options,
133 NotableFlags *notable_flags,
134 vector<string> *completions);
136 static void RetrieveUnusedFlags(
137 const set<const CommandLineFlagInfo *> &matching_flags,
138 const NotableFlags ¬able_flags,
139 set<const CommandLineFlagInfo *> *unused_flags);
143 static void OutputSingleGroupWithLimit(
144 const set<const CommandLineFlagInfo *> &group,
145 const string &line_indentation,
146 const string &header,
147 const string &footer,
148 bool long_output_format,
149 int *remaining_line_limit,
150 size_t *completion_elements_added,
151 vector<string> *completions);
154 static string GetShortFlagLine(
155 const string &line_indentation,
156 const CommandLineFlagInfo &info);
158 static string GetLongFlagLine(
159 const string &line_indentation,
160 const CommandLineFlagInfo &info);
166 // Try to deduce the intentions behind this completion attempt. Return the
167 // canonical search term in 'canonical_search_token'. Binary search options
168 // are returned in the various booleans, which should all have intuitive
169 // semantics, possibly except:
170 // - return_all_matching_flags: Generally, we'll trim the number of
171 // returned candidates to some small number, showing those that are
172 // most likely to be useful first. If this is set, however, the user
173 // really does want us to return every single flag as an option.
174 // - force_no_update: Any time we output lines, all of which share a
175 // common prefix, bash will 'helpfully' not even bother to show the
176 // output, instead changing the current word to be that common prefix.
177 // If it's clear this shouldn't happen, we'll set this boolean
178 struct CompletionOptions {
179 bool flag_name_substring_search;
180 bool flag_location_substring_search;
181 bool flag_description_substring_search;
182 bool return_all_matching_flags;
183 bool force_no_update;
186 // Notable flags are flags that are special or preferred for some
187 // reason. For example, flags that are defined in the binary's module
188 // are expected to be much more relevent than flags defined in some
189 // other random location. These sets are specified roughly in precedence
190 // order. Once a flag is placed in one of these 'higher' sets, it won't
191 // be placed in any of the 'lower' sets.
192 struct NotableFlags {
193 typedef set<const CommandLineFlagInfo *> FlagSet;
194 FlagSet perfect_match_flag;
195 FlagSet module_flags; // Found in module file
196 FlagSet package_flags; // Found in same directory as module file
197 FlagSet most_common_flags; // One of the XXX most commonly supplied flags
198 FlagSet subpackage_flags; // Found in subdirectories of package
203 // Tab completion implementation - entry point
204 static void PrintFlagCompletionInfo(void) {
205 string cursor_word = FLAGS_tab_completion_word;
206 string canonical_token;
207 CompletionOptions options = { };
208 CanonicalizeCursorWordAndSearchOptions(
213 //VLOG(1) << "Identified canonical_token: '" << canonical_token << "'";
215 vector<CommandLineFlagInfo> all_flags;
216 set<const CommandLineFlagInfo *> matching_flags;
217 GetAllFlags(&all_flags);
218 //VLOG(2) << "Found " << all_flags.size() << " flags overall";
220 string longest_common_prefix;
226 &longest_common_prefix);
227 //VLOG(1) << "Identified " << matching_flags.size() << " matching flags";
228 //VLOG(1) << "Identified " << longest_common_prefix
229 // << " as longest common prefix.";
230 if (longest_common_prefix.size() > canonical_token.size()) {
231 // There's actually a shared common prefix to all matching flags,
232 // so may as well output that and quit quickly.
233 //VLOG(1) << "The common prefix '" << longest_common_prefix
234 // << "' was longer than the token '" << canonical_token
235 // << "'. Returning just this prefix for completion.";
236 fprintf(stdout, "--%s", longest_common_prefix.c_str());
239 if (matching_flags.empty()) {
240 //VLOG(1) << "There were no matching flags, returning nothing.";
246 TryFindModuleAndPackageDir(all_flags, &module, &package_dir);
247 //VLOG(1) << "Identified module: '" << module << "'";
248 //VLOG(1) << "Identified package_dir: '" << package_dir << "'";
250 NotableFlags notable_flags;
251 CategorizeAllMatchingFlags(
257 //VLOG(2) << "Categorized matching flags:";
258 //VLOG(2) << " perfect_match: " << notable_flags.perfect_match_flag.size();
259 //VLOG(2) << " module: " << notable_flags.module_flags.size();
260 //VLOG(2) << " package: " << notable_flags.package_flags.size();
261 //VLOG(2) << " most common: " << notable_flags.most_common_flags.size();
262 //VLOG(2) << " subpackage: " << notable_flags.subpackage_flags.size();
264 vector<string> completions;
265 FinalizeCompletionOutput(
271 if (options.force_no_update)
272 completions.push_back("~");
274 //VLOG(1) << "Finalized with " << completions.size()
275 // << " chosen completions";
277 for (vector<string>::const_iterator it = completions.begin();
278 it != completions.end();
280 //VLOG(9) << " Completion entry: '" << *it << "'";
281 fprintf(stdout, "%s\n", it->c_str());
286 // 1) Examine search word (and helper method)
287 static void CanonicalizeCursorWordAndSearchOptions(
288 const string &cursor_word,
289 string *canonical_search_token,
290 CompletionOptions *options) {
291 *canonical_search_token = cursor_word;
292 if (canonical_search_token->empty()) return;
294 // Get rid of leading quotes and dashes in the search term
295 if ((*canonical_search_token)[0] == '"')
296 *canonical_search_token = canonical_search_token->substr(1);
297 while ((*canonical_search_token)[0] == '-')
298 *canonical_search_token = canonical_search_token->substr(1);
300 options->flag_name_substring_search = false;
301 options->flag_location_substring_search = false;
302 options->flag_description_substring_search = false;
303 options->return_all_matching_flags = false;
304 options->force_no_update = false;
306 // Look for all search options we can deduce now. Do this by walking
307 // backwards through the term, looking for up to three '?' and up to
308 // one '+' as suffixed characters. Consume them if found, and remove
309 // them from the canonical search token.
310 int found_question_marks = 0;
311 int found_plusses = 0;
313 if (found_question_marks < 3 &&
314 RemoveTrailingChar(canonical_search_token, '?')) {
315 ++found_question_marks;
318 if (found_plusses < 1 &&
319 RemoveTrailingChar(canonical_search_token, '+')) {
326 switch (found_question_marks) { // all fallthroughs
327 case 3: options->flag_description_substring_search = true;
328 case 2: options->flag_location_substring_search = true;
329 case 1: options->flag_name_substring_search = true;
332 options->return_all_matching_flags = (found_plusses > 0);
335 // Returns true if a char was removed
336 static bool RemoveTrailingChar(string *str, char c) {
337 if (str->empty()) return false;
338 if ((*str)[str->size() - 1] == c) {
339 *str = str->substr(0, str->size() - 1);
346 // 2) Find all matches (and helper methods)
347 static void FindMatchingFlags(
348 const vector<CommandLineFlagInfo> &all_flags,
349 const CompletionOptions &options,
350 const string &match_token,
351 set<const CommandLineFlagInfo *> *all_matches,
352 string *longest_common_prefix) {
353 all_matches->clear();
354 bool first_match = true;
355 for (vector<CommandLineFlagInfo>::const_iterator it = all_flags.begin();
356 it != all_flags.end();
358 if (DoesSingleFlagMatch(*it, options, match_token)) {
359 all_matches->insert(&*it);
362 *longest_common_prefix = it->name;
364 if (longest_common_prefix->empty() || it->name.empty()) {
365 longest_common_prefix->clear();
368 string::size_type pos = 0;
369 while (pos < longest_common_prefix->size() &&
370 pos < it->name.size() &&
371 (*longest_common_prefix)[pos] == it->name[pos])
373 longest_common_prefix->erase(pos);
379 // Given the set of all flags, the parsed match options, and the
380 // canonical search token, produce the set of all candidate matching
381 // flags for subsequent analysis or filtering.
382 static bool DoesSingleFlagMatch(
383 const CommandLineFlagInfo &flag,
384 const CompletionOptions &options,
385 const string &match_token) {
386 // Is there a prefix match?
387 string::size_type pos = flag.name.find(match_token);
388 if (pos == 0) return true;
390 // Is there a substring match if we want it?
391 if (options.flag_name_substring_search &&
395 // Is there a location match if we want it?
396 if (options.flag_location_substring_search &&
397 flag.filename.find(match_token) != string::npos)
400 // TODO(daven): All searches should probably be case-insensitive
401 // (especially this one...)
402 if (options.flag_description_substring_search &&
403 flag.description.find(match_token) != string::npos)
409 // 3) Categorize matches (and helper method)
411 // Given a set of matching flags, categorize them by
412 // likely relevence to this specific binary
413 static void CategorizeAllMatchingFlags(
414 const set<const CommandLineFlagInfo *> &all_matches,
415 const string &search_token,
416 const string &module, // empty if we couldn't find any
417 const string &package_dir, // empty if we couldn't find any
418 NotableFlags *notable_flags) {
419 notable_flags->perfect_match_flag.clear();
420 notable_flags->module_flags.clear();
421 notable_flags->package_flags.clear();
422 notable_flags->most_common_flags.clear();
423 notable_flags->subpackage_flags.clear();
425 for (set<const CommandLineFlagInfo *>::const_iterator it =
427 it != all_matches.end();
429 //VLOG(2) << "Examining match '" << (*it)->name << "'";
430 //VLOG(7) << " filename: '" << (*it)->filename << "'";
431 string::size_type pos = string::npos;
432 if (!package_dir.empty())
433 pos = (*it)->filename.find(package_dir);
434 string::size_type slash = string::npos;
435 if (pos != string::npos) // candidate for package or subpackage match
436 slash = (*it)->filename.find(
438 pos + package_dir.size() + 1);
440 if ((*it)->name == search_token) {
441 // Exact match on some flag's name
442 notable_flags->perfect_match_flag.insert(*it);
443 //VLOG(3) << "Result: perfect match";
444 } else if (!module.empty() && (*it)->filename == module) {
445 // Exact match on module filename
446 notable_flags->module_flags.insert(*it);
447 //VLOG(3) << "Result: module match";
448 } else if (!package_dir.empty() &&
449 pos != string::npos && slash == string::npos) {
450 // In the package, since there was no slash after the package portion
451 notable_flags->package_flags.insert(*it);
452 //VLOG(3) << "Result: package match";
454 // In the list of the XXX most commonly supplied flags overall
455 // TODO(daven): Compile this list.
456 //VLOG(3) << "Result: most-common match";
457 } else if (!package_dir.empty() &&
458 pos != string::npos && slash != string::npos) {
459 // In a subdirectory of the package
460 notable_flags->subpackage_flags.insert(*it);
461 //VLOG(3) << "Result: subpackage match";
464 //VLOG(3) << "Result: not special match";
468 static void PushNameWithSuffix(vector<string>* suffixes, const char* suffix) {
470 s += ProgramInvocationShortName();
472 suffixes->push_back(s);
475 static void TryFindModuleAndPackageDir(
476 const vector<CommandLineFlagInfo> all_flags,
478 string *package_dir) {
480 package_dir->clear();
482 vector<string> suffixes;
483 // TODO(daven): There's some inherant ambiguity here - multiple directories
484 // could share the same trailing folder and file structure (and even worse,
485 // same file names), causing us to be unsure as to which of the two is the
486 // actual package for this binary. In this case, we'll arbitrarily choose.
487 PushNameWithSuffix(&suffixes, ".");
488 PushNameWithSuffix(&suffixes, "-main.");
489 PushNameWithSuffix(&suffixes, "_main.");
490 // These four are new but probably merited?
491 PushNameWithSuffix(&suffixes, "-test.");
492 PushNameWithSuffix(&suffixes, "_test.");
493 PushNameWithSuffix(&suffixes, "-unittest.");
494 PushNameWithSuffix(&suffixes, "_unittest.");
496 for (vector<CommandLineFlagInfo>::const_iterator it = all_flags.begin();
497 it != all_flags.end();
499 for (vector<string>::const_iterator suffix = suffixes.begin();
500 suffix != suffixes.end();
502 // TODO(daven): Make sure the match is near the end of the string
503 if (it->filename.find(*suffix) != string::npos) {
504 *module = it->filename;
505 string::size_type sep = it->filename.rfind(PATH_SEPARATOR);
506 *package_dir = it->filename.substr(0, (sep == string::npos) ? 0 : sep);
513 // Can't specialize template type on a locally defined type. Silly C++...
514 struct DisplayInfoGroup {
517 set<const CommandLineFlagInfo *> *group;
519 int SizeInLines() const {
520 int size_in_lines = static_cast<int>(group->size()) + 1;
521 if (strlen(header) > 0) {
524 if (strlen(footer) > 0) {
527 return size_in_lines;
531 // 4) Finalize and trim output flag set
532 static void FinalizeCompletionOutput(
533 const set<const CommandLineFlagInfo *> &matching_flags,
534 CompletionOptions *options,
535 NotableFlags *notable_flags,
536 vector<string> *completions) {
538 // We want to output lines in groups. Each group needs to be indented
539 // the same to keep its lines together. Unless otherwise required,
540 // only 99 lines should be output to prevent bash from harassing the
543 // First, figure out which output groups we'll actually use. For each
544 // nonempty group, there will be ~3 lines of header & footer, plus all
545 // output lines themselves.
546 int max_desired_lines = // "999999 flags should be enough for anyone. -dave"
547 (options->return_all_matching_flags ? 999999 : 98);
548 int lines_so_far = 0;
550 vector<DisplayInfoGroup> output_groups;
551 bool perfect_match_found = false;
552 if (lines_so_far < max_desired_lines &&
553 !notable_flags->perfect_match_flag.empty()) {
554 perfect_match_found = true;
555 DisplayInfoGroup group =
558 ¬able_flags->perfect_match_flag };
559 lines_so_far += group.SizeInLines();
560 output_groups.push_back(group);
562 if (lines_so_far < max_desired_lines &&
563 !notable_flags->module_flags.empty()) {
564 DisplayInfoGroup group = {
565 "-* Matching module flags *-",
566 "===========================",
567 ¬able_flags->module_flags };
568 lines_so_far += group.SizeInLines();
569 output_groups.push_back(group);
571 if (lines_so_far < max_desired_lines &&
572 !notable_flags->package_flags.empty()) {
573 DisplayInfoGroup group = {
574 "-* Matching package flags *-",
575 "============================",
576 ¬able_flags->package_flags };
577 lines_so_far += group.SizeInLines();
578 output_groups.push_back(group);
580 if (lines_so_far < max_desired_lines &&
581 !notable_flags->most_common_flags.empty()) {
582 DisplayInfoGroup group = {
583 "-* Commonly used flags *-",
584 "=========================",
585 ¬able_flags->most_common_flags };
586 lines_so_far += group.SizeInLines();
587 output_groups.push_back(group);
589 if (lines_so_far < max_desired_lines &&
590 !notable_flags->subpackage_flags.empty()) {
591 DisplayInfoGroup group = {
592 "-* Matching sub-package flags *-",
593 "================================",
594 ¬able_flags->subpackage_flags };
595 lines_so_far += group.SizeInLines();
596 output_groups.push_back(group);
599 set<const CommandLineFlagInfo *> obscure_flags; // flags not notable
600 if (lines_so_far < max_desired_lines) {
601 RetrieveUnusedFlags(matching_flags, *notable_flags, &obscure_flags);
602 if (!obscure_flags.empty()) {
603 DisplayInfoGroup group = {
607 lines_so_far += group.SizeInLines();
608 output_groups.push_back(group);
612 // Second, go through each of the chosen output groups and output
613 // as many of those flags as we can, while remaining below our limit
614 int remaining_lines = max_desired_lines;
615 size_t completions_output = 0;
616 int indent = static_cast<int>(output_groups.size()) - 1;
617 for (vector<DisplayInfoGroup>::const_iterator it =
618 output_groups.begin();
619 it != output_groups.end();
621 OutputSingleGroupWithLimit(
623 string(indent, ' '), // line indentation
624 string(it->header), // header
625 string(it->footer), // footer
626 perfect_match_found, // long format
627 &remaining_lines, // line limit - reduces this by number printed
628 &completions_output, // completions (not lines) added
629 completions); // produced completions
630 perfect_match_found = false;
633 if (completions_output != matching_flags.size()) {
634 options->force_no_update = false;
635 completions->push_back("~ (Remaining flags hidden) ~");
637 options->force_no_update = true;
641 static void RetrieveUnusedFlags(
642 const set<const CommandLineFlagInfo *> &matching_flags,
643 const NotableFlags ¬able_flags,
644 set<const CommandLineFlagInfo *> *unused_flags) {
645 // Remove from 'matching_flags' set all members of the sets of
646 // flags we've already printed (specifically, those in notable_flags)
647 for (set<const CommandLineFlagInfo *>::const_iterator it =
648 matching_flags.begin();
649 it != matching_flags.end();
651 if (notable_flags.perfect_match_flag.count(*it) ||
652 notable_flags.module_flags.count(*it) ||
653 notable_flags.package_flags.count(*it) ||
654 notable_flags.most_common_flags.count(*it) ||
655 notable_flags.subpackage_flags.count(*it))
657 unused_flags->insert(*it);
661 // 5) Output matches (and helper methods)
663 static void OutputSingleGroupWithLimit(
664 const set<const CommandLineFlagInfo *> &group,
665 const string &line_indentation,
666 const string &header,
667 const string &footer,
668 bool long_output_format,
669 int *remaining_line_limit,
670 size_t *completion_elements_output,
671 vector<string> *completions) {
672 if (group.empty()) return;
673 if (!header.empty()) {
674 if (*remaining_line_limit < 2) return;
675 *remaining_line_limit -= 2;
676 completions->push_back(line_indentation + header);
677 completions->push_back(line_indentation + string(header.size(), '-'));
679 for (set<const CommandLineFlagInfo *>::const_iterator it = group.begin();
680 it != group.end() && *remaining_line_limit > 0;
682 --*remaining_line_limit;
683 ++*completion_elements_output;
684 completions->push_back(
686 ? GetLongFlagLine(line_indentation, **it)
687 : GetShortFlagLine(line_indentation, **it)));
689 if (!footer.empty()) {
690 if (*remaining_line_limit < 1) return;
691 --*remaining_line_limit;
692 completions->push_back(line_indentation + footer);
696 static string GetShortFlagLine(
697 const string &line_indentation,
698 const CommandLineFlagInfo &info) {
700 line_indentation + "--" + info.name + " [" +
701 (info.type == "string" ?
702 ("'" + info.default_value + "'") :
706 FLAGS_tab_completion_columns - static_cast<int>(prefix.size());
710 (static_cast<int>(info.description.size()) > remainder ?
711 (info.description.substr(0, remainder - 3) + "...").c_str() :
712 info.description.c_str());
713 return prefix + suffix;
716 static string GetLongFlagLine(
717 const string &line_indentation,
718 const CommandLineFlagInfo &info) {
720 string output = DescribeOneFlag(info);
722 // Replace '-' with '--', and remove trailing newline before appending
723 // the module definition location.
724 string old_flagname = "-" + info.name;
726 output.find(old_flagname),
729 // Stick a newline and indentation in front of the type and default
730 // portions of DescribeOneFlag()s description
731 static const char kNewlineWithIndent[] = "\n ";
732 output.replace(output.find(" type:"), 1, string(kNewlineWithIndent));
733 output.replace(output.find(" default:"), 1, string(kNewlineWithIndent));
734 output = line_indentation + " Details for '--" + info.name + "':\n" +
735 output + " defined: " + info.filename;
737 // Eliminate any doubled newlines that crept in. Specifically, if
738 // DescribeOneFlag() decided to break the line just before "type"
739 // or "default", we don't want to introduce an extra blank line
740 static const string line_of_spaces(FLAGS_tab_completion_columns, ' ');
741 static const char kDoubledNewlines[] = "\n \n";
742 for (string::size_type newlines = output.find(kDoubledNewlines);
743 newlines != string::npos;
744 newlines = output.find(kDoubledNewlines))
745 // Replace each 'doubled newline' with a single newline
746 output.replace(newlines, sizeof(kDoubledNewlines) - 1, string("\n"));
748 for (string::size_type newline = output.find('\n');
749 newline != string::npos;
750 newline = output.find('\n')) {
751 int newline_pos = static_cast<int>(newline) % FLAGS_tab_completion_columns;
752 int missing_spaces = FLAGS_tab_completion_columns - newline_pos;
753 output.replace(newline, 1, line_of_spaces, 1, missing_spaces);
759 void HandleCommandLineCompletions(void) {
760 if (FLAGS_tab_completion_word.empty()) return;
761 PrintFlagCompletionInfo();
765 _END_GOOGLE_NAMESPACE_