ripgrep: add --pre-glob flag

The --pre-glob flag is like the --glob flag, except it applies to filtering
files through the preprocessor instead of for search. This makes it
possible to apply the preprocessor to only a small subset of files, which
can greatly reduce the process overhead of using a preprocessor when
searching large directories.

6 files changed, 159 insertions, 59 deletions

diff --git a/CHANGELOG.md b/CHANGELOG.md
index 226ca6a7..f757f550 100644
--- a/CHANGELOG.md
+++ b/CHANGELOG.md
@@ -46,6 +46,8 @@ Feature enhancements:
   The `--passthru` flag now works with the `--replace` flag.
 * FEATURE:
   Add `--line-buffered` and `--block-buffered` for forcing a buffer strategy.
+* FEATURE:
+  Add `--pre-glob` for filtering files through the `--pre` flag.
 
 Bug fixes:
 
diff --git a/complete/_rg b/complete/_rg
index 2bbdf992..6f7b0ef8 100644
--- a/complete/_rg
+++ b/complete/_rg
@@ -183,6 +183,9 @@ _rg() {
     '(-z --search-zip)--pre=[specify preprocessor utility]:preprocessor utility:_command_names -e'
     $no'--no-pre[disable preprocessor utility]'
 
+    + pre-glob # Preprocessing glob options
+    '*--pre-glob[include/exclude files for preprocessing with --pre]'
+
     + '(pretty-vimgrep)' # Pretty/vimgrep display options
     '(heading)'{-p,--pretty}'[alias for --color=always --heading -n]'
     '(heading passthru)--vimgrep[show results in vim-compatible format]'
diff --git a/src/app.rs b/src/app.rs
index e0e1eda7..03239277 100644
--- a/src/app.rs
+++ b/src/app.rs
@@ -598,6 +598,7 @@ pub fn all_args_and_flags() -> Vec<RGArg> {
     flag_passthru(&mut args);
     flag_pcre2(&mut args);
     flag_pre(&mut args);
+    flag_pre_glob(&mut args);
     flag_pretty(&mut args);
     flag_quiet(&mut args);
     flag_regex_size_limit(&mut args);
@@ -1819,6 +1820,97 @@ This flag can be disabled with --no-pcre2.
     args.push(arg);
 }
 
+fn flag_pre(args: &mut Vec<RGArg>) {
+    const SHORT: &str = "search outputs of COMMAND FILE for each FILE";
+    const LONG: &str = long!("\
+For each input FILE, search the standard output of COMMAND FILE rather than the
+contents of FILE. This option expects the COMMAND program to either be an
+absolute path or to be available in your PATH. Either an empty string COMMAND
+or the `--no-pre` flag will disable this behavior.
+
+    WARNING: When this flag is set, ripgrep will unconditionally spawn a
+    process for every file that is searched. Therefore, this can incur an
+    unnecessarily large performance penalty if you don't otherwise need the
+    flexibility offered by this flag.
+
+A preprocessor is not run when ripgrep is searching stdin.
+
+When searching over sets of files that may require one of several decoders
+as preprocessors, COMMAND should be a wrapper program or script which first
+classifies FILE based on magic numbers/content or based on the FILE name and
+then dispatches to an appropriate preprocessor. Each COMMAND also has its
+standard input connected to FILE for convenience.
+
+For example, a shell script for COMMAND might look like:
+
+    case \"$1\" in
+    *.pdf)
+        exec pdftotext \"$1\" -
+        ;;
+    *)
+        case $(file \"$1\") in
+        *Zstandard*)
+            exec pzstd -cdq
+            ;;
+        *)
+            exec cat
+            ;;
+        esac
+        ;;
+    esac
+
+The above script uses `pdftotext` to convert a PDF file to plain text. For
+all other files, the script uses the `file` utility to sniff the type of the
+file based on its contents. If it is a compressed file in the Zstandard format,
+then `pzstd` is used to decompress the contents to stdout.
+
+This overrides the -z/--search-zip flag.
+");
+    let arg = RGArg::flag("pre", "COMMAND")
+        .help(SHORT).long_help(LONG)
+        .overrides("no-pre")
+        .overrides("search-zip");
+    args.push(arg);
+
+    let arg = RGArg::switch("no-pre")
+        .hidden()
+        .overrides("pre");
+    args.push(arg);
+}
+
+fn flag_pre_glob(args: &mut Vec<RGArg>) {
+    const SHORT: &str =
+        "Include or exclude files from a preprocessing command.";
+    const LONG: &str = long!("\
+This flag works in conjunction with the --pre flag. Namely, when one or more
+--pre-glob flags are given, then only files that match the given set of globs
+will be handed to the command specified by the --pre flag. Any non-matching
+files will be searched without using the preprocessor command.
+
+This flag is useful when searching many files with the --pre flag. Namely,
+it permits the ability to avoid process overhead for files that don't need
+preprocessing. For example, given the following shell script, 'pre-pdftotext':
+
+    #!/bin/sh
+
+    pdftotext \"$1\" -
+
+then it is possible to use '--pre pre-pdftotext --pre-glob \'*.pdf\'' to make
+it so ripgrep only executes the 'pre-pdftotext' command on files with a '.pdf'
+extension.
+
+Multiple --pre-glob flags may be used. Globbing rules match .gitignore globs.
+Precede a glob with a ! to exclude it.
+
+This flag has no effect if the --pre flag is not used.
+");
+    let arg = RGArg::flag("pre-glob", "GLOB")
+        .help(SHORT).long_help(LONG)
+        .multiple()
+        .allow_leading_hyphen();
+    args.push(arg);
+}
+
 fn flag_pretty(args: &mut Vec<RGArg>) {
     const SHORT: &str = "Alias for --color always --heading --line-number.";
     const LONG: &str = long!("\
@@ -1924,64 +2016,6 @@ This flag can be disabled with --no-search-zip.
     args.push(arg);
 }
 
-fn flag_pre(args: &mut Vec<RGArg>) {
-    const SHORT: &str = "search outputs of COMMAND FILE for each FILE";
-    const LONG: &str = long!("\
-For each input FILE, search the standard output of COMMAND FILE rather than the
-contents of FILE. This option expects the COMMAND program to either be an
-absolute path or to be available in your PATH. Either an empty string COMMAND
-or the `--no-pre` flag will disable this behavior.
-
-    WARNING: When this flag is set, ripgrep will unconditionally spawn a
-    process for every file that is searched. Therefore, this can incur an
-    unnecessarily large performance penalty if you don't otherwise need the
-    flexibility offered by this flag.
-
-A preprocessor is not run when ripgrep is searching stdin.
-
-When searching over sets of files that may require one of several decoders
-as preprocessors, COMMAND should be a wrapper program or script which first
-classifies FILE based on magic numbers/content or based on the FILE name and
-then dispatches to an appropriate preprocessor. Each COMMAND also has its
-standard input connected to FILE for convenience.
-
-For example, a shell script for COMMAND might look like:
-
-    case \"$1\" in
-    *.pdf)
-        exec pdftotext \"$1\" -
-        ;;
-    *)
-        case $(file \"$1\") in
-        *Zstandard*)
-            exec pzstd -cdq
-            ;;
-        *)
-            exec cat
-            ;;
-        esac
-        ;;
-    esac
-
-The above script uses `pdftotext` to convert a PDF file to plain text. For
-all other files, the script uses the `file` utility to sniff the type of the
-file based on its contents. If it is a compressed file in the Zstandard format,
-then `pzstd` is used to decompress the contents to stdout.
-
-This overrides the -z/--search-zip flag.
-");
-    let arg = RGArg::flag("pre", "COMMAND")
-        .help(SHORT).long_help(LONG)
-        .overrides("no-pre")
-        .overrides("search-zip");
-    args.push(arg);
-
-    let arg = RGArg::switch("no-pre")
-        .hidden()
-        .overrides("pre");
-    args.push(arg);
-}
-
 fn flag_smart_case(args: &mut Vec<RGArg>) {
     const SHORT: &str = "Smart case search.";
     const LONG: &str = long!("\
diff --git a/src/args.rs b/src/args.rs
index f8a29cae..1a38d3ef 100644
--- a/src/args.rs
+++ b/src/args.rs
@@ -285,6 +285,7 @@ impl Args {
         builder
             .json_stats(self.matches().is_present("json"))
             .preprocessor(self.matches().preprocessor())
+            .preprocessor_globs(self.matches().preprocessor_globs()?)
             .search_zip(self.matches().is_present("search-zip"));
         Ok(builder.build(matcher, searcher, printer))
     }
@@ -1323,6 +1324,17 @@ impl ArgMatches {
         Some(Path::new(path).to_path_buf())
     }
 
+    /// Builds the set of globs for filtering files to apply to the --pre
+    /// flag. If no --pre-globs are available, then this always returns an
+    /// empty set of globs.
+    fn preprocessor_globs(&self) -> Result<Override> {
+        let mut builder = OverrideBuilder::new(env::current_dir()?);
+        for glob in self.values_of_lossy_vec("pre-glob") {
+            builder.add(&glob)?;
+        }
+        Ok(builder.build()?)
+    }
+
     /// Parse the regex-size-limit argument option into a byte count.
     fn regex_size_limit(&self) -> Result<Option<usize>> {
         let r = self.parse_human_readable_size("regex-size-limit")?;
diff --git a/src/search.rs b/src/search.rs
index 457f8f7a..9baf513f 100644
--- a/src/search.rs
+++ b/src/search.rs
@@ -11,6 +11,7 @@ use grep::pcre2::{RegexMatcher as PCRE2RegexMatcher};
 use grep::printer::{JSON, Standard, Summary, Stats};
 use grep::regex::{RegexMatcher as RustRegexMatcher};
 use grep::searcher::Searcher;
+use ignore::overrides::Override;
 use serde_json as json;
 use termcolor::WriteColor;
 
@@ -23,6 +24,7 @@ use subject::Subject;
 struct Config {
     json_stats: bool,
     preprocessor: Option<PathBuf>,
+    preprocessor_globs: Override,
     search_zip: bool,
 }
 
@@ -31,6 +33,7 @@ impl Default for Config {
         Config {
             json_stats: false,
             preprocessor: None,
+            preprocessor_globs: Override::empty(),
             search_zip: false,
         }
     }
@@ -108,6 +111,17 @@ impl SearchWorkerBuilder {
         self
     }
 
+    /// Set the globs for determining which files should be run through the
+    /// preprocessor. By default, with no globs and a preprocessor specified,
+    /// every file is run through the preprocessor.
+    pub fn preprocessor_globs(
+        &mut self,
+        globs: Override,
+    ) -> &mut SearchWorkerBuilder {
+        self.config.preprocessor_globs = globs;
+        self
+    }
+
     /// Enable the decompression and searching of common compressed files.
     ///
     /// When enabled, if a particular file path is recognized as a compressed
@@ -298,7 +312,7 @@ impl<W: WriteColor> SearchWorker<W> {
             let stdin = io::stdin();
             // A `return` here appeases the borrow checker. NLL will fix this.
             return self.search_reader(path, stdin.lock());
-        } else if self.config.preprocessor.is_some() {
+        } else if self.should_preprocess(path) {
             self.search_preprocessor(path)
         } else if self.should_decompress(path) {
             self.search_decompress(path)
@@ -316,6 +330,20 @@ impl<W: WriteColor> SearchWorker<W> {
         self.decomp_builder.get_matcher().has_command(path)
     }
 
+    /// Returns true if and only if the given file path should be run through
+    /// the preprocessor.
+    fn should_preprocess(&self, path: &Path) -> bool {
+        if !self.config.preprocessor.is_some() {
+            return false;
+        }
+        if self.config.preprocessor_globs.is_empty() {
+            return true;
+        }
+        !self.config.preprocessor_globs.matched(path, false).is_ignore()
+    }
+
+    /// Search the given file path by first asking the preprocessor for the
+    /// data to search instead of opening the path directly.
     fn search_preprocessor(
         &mut self,
         path: &Path,
@@ -333,6 +361,9 @@ impl<W: WriteColor> SearchWorker<W> {
         })
     }
 
+    /// Attempt to decompress the data at the given file path and search the
+    /// result. If the given file path isn't recognized as a compressed file,
+    /// then search it without doing any decompression.
     fn search_decompress(
         &mut self,
         path: &Path,
diff --git a/tests/misc.rs b/tests/misc.rs
index 62226ceb..9b5a7a75 100644
--- a/tests/misc.rs
+++ b/tests/misc.rs
@@ -816,6 +816,24 @@ be, to a very large extent, the result of luck. Sherlock Holmes
     eqnice!(expected, cmd.stdout());
 });
 
+rgtest!(preprocessing_glob, |dir: Dir, mut cmd: TestCommand| {
+    if !cmd_exists("xzcat") {
+        return;
+    }
+
+    dir.create("sherlock", SHERLOCK);
+    dir.create_bytes("sherlock.xz", include_bytes!("./data/sherlock.xz"));
+    cmd.args(&["--pre", "xzcat", "--pre-glob", "*.xz", "Sherlock"]);
+
+    let expected = "\
+sherlock.xz:For the Doctor Watsons of this world, as opposed to the Sherlock
+sherlock.xz:be, to a very large extent, the result of luck. Sherlock Holmes
+sherlock:For the Doctor Watsons of this world, as opposed to the Sherlock
+sherlock:be, to a very large extent, the result of luck. Sherlock Holmes
+";
+    eqnice!(sort_lines(expected), sort_lines(&cmd.stdout()));
+});
+
 rgtest!(compressed_gzip, |dir: Dir, mut cmd: TestCommand| {
     if !cmd_exists("gzip") {
         return;