Strip dependencies of bat-as-a-library

13 files changed, 104 insertions, 81 deletions

diff --git a/Cargo.toml b/Cargo.toml
index 98a0fdc2..d7ba56b2 100644
--- a/Cargo.toml
+++ b/Cargo.toml
@@ -15,14 +15,27 @@ exclude = [
 build = "build.rs"
 edition = '2018'
 
+[features]
+default = ["application"]
+# Feature required for bat the application. Should be disabled when depending on
+# bat as a library.
+application = [
+    "atty",
+    "clap",
+    "dirs",
+    "lazy_static",
+    "liquid",
+    "wild",
+]
+
 [dependencies]
-atty = "0.2.14"
+atty = { version = "0.2.14", optional = true }
 ansi_term = "^0.12.1"
 ansi_colours = "^1.0"
 console = "0.10"
-dirs = "2.0"
-lazy_static = "1.4"
-wild = "2.0"
+dirs = { version = "2.0", optional = true }
+lazy_static = { version = "1.4", optional = true }
+wild = { version = "2.0", optional = true }
 content_inspector = "0.2.4"
 encoding = "0.2"
 shell-words = "0.1.0"
@@ -32,7 +45,6 @@ globset = "0.4"
 [dependencies.git2]
 version = "0.13"
 default-features = false
-features = []
 
 [dependencies.syntect]
 version = "3.2.0"
@@ -41,22 +53,22 @@ features = ["parsing", "yaml-load", "dump-load", "dump-create"]
 
 [dependencies.clap]
 version = "2.33"
+optional = true
 default-features = false
 features = ["suggestions", "color", "wrap_help"]
 
 [dependencies.error-chain]
 version = "0.12"
 default-features = false
-features = []
 
 [dev-dependencies]
 tempdir = "0.3"
 assert_cmd = "0.12.0"
 
 [build-dependencies]
-clap = "2.33"
-liquid = "0.20"
-lazy_static = "1.4"
+clap = { version = "2.33", optional = true }
+liquid = { version = "0.20", optional = true }
+lazy_static = { version = "1.4", optional = true }
 
 [profile.release]
 lto = true
diff --git a/build.rs b/build.rs
index bff88e9f..074caaff 100644
--- a/build.rs
+++ b/build.rs
@@ -1,38 +1,42 @@
 // TODO: Re-enable generation of shell completion files (below) when clap 3 is out.
 // For more details, see https://github.com/sharkdp/bat/issues/372
 
-#[macro_use]
-extern crate lazy_static;
-extern crate liquid;
-
-use std::error::Error;
-use std::fs;
-use std::path::Path;
-
-// Read environment variables.
-lazy_static! {
-    pub static ref PROJECT_NAME: &'static str = option_env!("PROJECT_NAME").unwrap_or("bat");
-    pub static ref PROJECT_VERSION: &'static str = option_env!("CARGO_PKG_VERSION").unwrap();
-    pub static ref EXECUTABLE_NAME: &'static str = option_env!("PROJECT_EXECUTABLE")
-        .or(option_env!("PROJECT_NAME"))
-        .unwrap_or("bat");
-}
-
-/// Generates a file from a liquid template.
-fn template(
-    variables: &liquid::Object,
-    in_file: &str,
-    out_file: impl AsRef<Path>,
-) -> Result<(), Box<dyn Error>> {
-    let template = liquid::ParserBuilder::with_stdlib()
-        .build()?
-        .parse(&fs::read_to_string(in_file)?)?;
-
-    fs::write(out_file, template.render(variables)?)?;
-    Ok(())
-}
+// For bat-as-a-library, no build script is required. The build script is for
+// the manpage and completions, which are only relevant to the bat application.
+#[cfg(not(feature = "application"))]
+fn main() {}
+
+#[cfg(feature = "application")]
+fn main() -> Result<(), Box<dyn std::error::Error>> {
+    use std::error::Error;
+    use std::fs;
+    use std::path::Path;
+
+    use lazy_static::lazy_static;
+
+    // Read environment variables.
+    lazy_static! {
+        static ref PROJECT_NAME: &'static str = option_env!("PROJECT_NAME").unwrap_or("bat");
+        static ref PROJECT_VERSION: &'static str = option_env!("CARGO_PKG_VERSION").unwrap();
+        static ref EXECUTABLE_NAME: &'static str = option_env!("PROJECT_EXECUTABLE")
+            .or(option_env!("PROJECT_NAME"))
+            .unwrap_or("bat");
+    }
+
+    /// Generates a file from a liquid template.
+    fn template(
+        variables: &liquid::Object,
+        in_file: &str,
+        out_file: impl AsRef<Path>,
+    ) -> Result<(), Box<dyn Error>> {
+        let template = liquid::ParserBuilder::with_stdlib()
+            .build()?
+            .parse(&fs::read_to_string(in_file)?)?;
+
+        fs::write(out_file, template.render(variables)?)?;
+        Ok(())
+    }
 
-fn main() -> Result<(), Box<dyn Error>> {
     let variables = liquid::object!({
         "PROJECT_NAME": PROJECT_NAME.to_owned(),
         "PROJECT_EXECUTABLE": EXECUTABLE_NAME.to_owned(),
diff --git a/ci/script.bash b/ci/script.bash
index db608c16..7f72ed34 100755
--- a/ci/script.bash
+++ b/ci/script.bash
@@ -12,3 +12,6 @@ if [[ $TARGET != arm-unknown-linux-gnueabihf ]] && [[ $TARGET != aarch64-unknown
     # Run 'bat' on its own source code and the README
     cargo run --target "$TARGET" -- src/bin/bat/main.rs README.md --paging=never
 fi
+
+# Check bat-as-a-library, which has a smaller set of dependencies
+cargo check --target "$TARGET" --verbose --lib --no-default-features
diff --git a/src/bin/bat/app.rs b/src/bin/bat/app.rs
index f1649b3f..56988b17 100644
--- a/src/bin/bat/app.rs
+++ b/src/bin/bat/app.rs
@@ -9,13 +9,9 @@ use crate::{
     config::{get_args_from_config_file, get_args_from_env_var},
 };
 use clap::ArgMatches;
-use wild;
 
 use console::Term;
 
-#[cfg(windows)]
-use ansi_term;
-
 use bat::{
     config::{
         Config, HighlightedLineRanges, InputFile, LineRange, LineRanges, MappingTarget, OutputWrap,
diff --git a/src/bin/bat/clap_app.rs b/src/bin/bat/clap_app.rs
index c2505ca9..c7344991 100644
--- a/src/bin/bat/clap_app.rs
+++ b/src/bin/bat/clap_app.rs
@@ -1,4 +1,4 @@
-use clap::{App as ClapApp, AppSettings, Arg, ArgGroup, SubCommand};
+use clap::{crate_name, crate_version, App as ClapApp, AppSettings, Arg, ArgGroup, SubCommand};
 use std::path::Path;
 
 pub fn build_app(interactive_output: bool) -> ClapApp<'static, 'static> {
diff --git a/src/bin/bat/config.rs b/src/bin/bat/config.rs
index 25c14d3b..8595ad5b 100644
--- a/src/bin/bat/config.rs
+++ b/src/bin/bat/config.rs
@@ -4,8 +4,6 @@ use std::fs;
 use std::io::{self, Write};
 use std::path::PathBuf;
 
-use shell_words;
-
 use crate::directories::PROJECT_DIRS;
 
 pub fn config_file() -> PathBuf {
diff --git a/src/bin/bat/directories.rs b/src/bin/bat/directories.rs
index e57a58c0..8f0f261d 100644
--- a/src/bin/bat/directories.rs
+++ b/src/bin/bat/directories.rs
@@ -1,7 +1,6 @@
 use std::env;
 use std::path::{Path, PathBuf};
 
-use dirs;
 use lazy_static::lazy_static;
 
 /// Wrapper for 'dirs' that treats MacOS more like Linux, by following the XDG specification.
diff --git a/src/bin/bat/main.rs b/src/bin/bat/main.rs
index 20130118..15cc37fa 100644
--- a/src/bin/bat/main.rs
+++ b/src/bin/bat/main.rs
@@ -1,11 +1,6 @@
 // `error_chain!` can recurse deeply
 #![recursion_limit = "1024"]
 
-#[macro_use]
-extern crate clap;
-
-extern crate dirs as dirs_rs;
-
 mod app;
 mod assets;
 mod clap_app;
diff --git a/src/errors.rs b/src/errors.rs
index a0f7e5eb..ff5682b9 100644
--- a/src/errors.rs
+++ b/src/errors.rs
@@ -2,20 +2,20 @@ use error_chain::error_chain;
 
 error_chain! {
     foreign_links {
-        Clap(::clap::Error);
-        Io(::std::io::Error);
-        SyntectError(::syntect::LoadingError);
-        ParseIntError(::std::num::ParseIntError);
-        GlobParsingError(::globset::Error);
+        Clap(clap::Error);
+        Io(std::io::Error);
+        SyntectError(syntect::LoadingError);
+        ParseIntError(std::num::ParseIntError);
+        GlobParsingError(globset::Error);
     }
 }
 
 pub fn default_error_handler(error: &Error) {
     match error {
         Error(ErrorKind::Io(ref io_error), _)
-            if io_error.kind() == ::std::io::ErrorKind::BrokenPipe =>
+            if io_error.kind() == std::io::ErrorKind::BrokenPipe =>
         {
-            ::std::process::exit(0);
+            std::process::exit(0);
         }
         _ => {
             use ansi_term::Colour::Red;
@@ -23,3 +23,36 @@ pub fn default_error_handler(error: &Error) {
         }
     };
 }
+
+// Mock out a type for clap::Error if we aren't pulling in a dependency on clap.
+//
+// This can be removed after migrating away from error_chain to some modern
+// derive-based error library such as thiserror, in favor of:
+//
+//     #[derive(Error)]
+//     pub enum Error {
+//         #[cfg(feature = "application")]
+//         Clap(clap::Error),
+//         ...
+//     }
+//
+#[cfg(not(feature = "application"))]
+mod clap {
+    use std::fmt::{self, Debug, Display};
+
+    pub struct Error(());
+
+    impl Display for Error {
+        fn fmt(&self, _formatter: &mut fmt::Formatter) -> fmt::Result {
+            unreachable!()
+        }
+    }
+
+    impl Debug for Error {
+        fn fmt(&self, _formatter: &mut fmt::Formatter) -> fmt::Result {
+            unreachable!()
+        }
+    }
+
+    impl std::error::Error for Error {}
+}
diff --git a/src/lib.rs b/src/lib.rs
index 8178f497..404ad49c 100644
--- a/src/lib.rs
+++ b/src/lib.rs
@@ -1,17 +1,6 @@
 // `error_chain!` can recurse deeply
 #![recursion_limit = "1024"]
 
-extern crate ansi_term;
-extern crate atty;
-extern crate console;
-extern crate content_inspector;
-extern crate dirs as dirs_rs;
-extern crate encoding;
-extern crate git2;
-extern crate shell_words;
-extern crate syntect;
-extern crate wild;
-
 pub(crate) mod assets;
 pub mod config;
 pub(crate) mod controller;
diff --git a/src/output.rs b/src/output.rs
index 3bad301b..134ab7b5 100644
--- a/src/output.rs
+++ b/src/output.rs
@@ -4,8 +4,6 @@ use std::io::{self, Write};
 use std::path::PathBuf;
 use std::process::{Child, Command, Stdio};
 
-use shell_words;
-
 use crate::config::PagingMode;
 use crate::errors::*;
 use crate::less::retrieve_less_version;
diff --git a/src/terminal.rs b/src/terminal.rs
index 8c3766c5..981bf3b2 100644
--- a/src/terminal.rs
+++ b/src/terminal.rs
@@ -1,5 +1,3 @@
-extern crate ansi_colours;
-
 use ansi_term::Colour::{Fixed, RGB};
 use ansi_term::{self, Style};
 
diff --git a/tests/tester.rs b/tests/tester.rs
index a761babe..9c52459f 100644
--- a/tests/tester.rs
+++ b/tests/tester.rs
@@ -4,13 +4,11 @@ use std::io::Read;
 use std::path::{Path, PathBuf};
 use std::process::Command;
 
-extern crate tempdir;
-use self::tempdir::TempDir;
+use tempdir::TempDir;
 
-extern crate git2;
-use self::git2::build::CheckoutBuilder;
-use self::git2::Repository;
-use self::git2::Signature;
+use git2::build::CheckoutBuilder;
+use git2::Repository;
+use git2::Signature;
 
 pub struct BatTester {
     /// Temporary working directory