From 25bcb61319ea172f4fb8028586239b2fa2fd221f Mon Sep 17 00:00:00 2001
From: Matthias Beyer <mail@beyermatthias.de>
Date: Mon, 23 Mar 2020 15:22:15 +0100
Subject: Add blackhole as default cli option

Signed-off-by: Matthias Beyer <mail@beyermatthias.de>
---
 lib/core/libimagrt/Cargo.toml     |  1 +
 lib/core/libimagrt/src/lib.rs     |  1 +
 lib/core/libimagrt/src/runtime.rs | 35 ++++++++++++++++++++++++++++++-----
 3 files changed, 32 insertions(+), 5 deletions(-)

diff --git a/lib/core/libimagrt/Cargo.toml b/lib/core/libimagrt/Cargo.toml
index d6792b51..fc1a2d29 100644
--- a/lib/core/libimagrt/Cargo.toml
+++ b/lib/core/libimagrt/Cargo.toml
@@ -27,6 +27,7 @@ itertools = "0.8.0"
 ansi_term = "0.12"
 atty = "0.2.11"
 anyhow = "1"
+indoc = "0.3"
 
 serde_derive = "1.0.94"
 serde = "1.0.94"
diff --git a/lib/core/libimagrt/src/lib.rs b/lib/core/libimagrt/src/lib.rs
index c36e2d01..224fa361 100644
--- a/lib/core/libimagrt/src/lib.rs
+++ b/lib/core/libimagrt/src/lib.rs
@@ -44,6 +44,7 @@ extern crate handlebars;
 extern crate serde;
 #[macro_use] extern crate anyhow;
 #[macro_use] extern crate toml_query;
+#[macro_use] extern crate indoc;
 
 extern crate clap;
 extern crate toml;
diff --git a/lib/core/libimagrt/src/runtime.rs b/lib/core/libimagrt/src/runtime.rs
index 90ad0920..aaa89772 100644
--- a/lib/core/libimagrt/src/runtime.rs
+++ b/lib/core/libimagrt/src/runtime.rs
@@ -61,6 +61,7 @@ pub struct Runtime<'a> {
 
     input_data: bool,
     output_data: bool,
+    blackhole_stdout: bool,
 }
 
 impl<'a> Runtime<'a> {
@@ -138,15 +139,17 @@ impl<'a> Runtime<'a> {
             Store::new(storepath, &config)
         };
 
-        let has_output_pipe = !atty::is(atty::Stream::Stdout);
-        let has_input_pipe  = !atty::is(atty::Stream::Stdin);
-        let input_data      = matches.is_present("input-pipe-data");
-        let output_data     = matches.is_present("output-pipe-data");
+        let has_output_pipe  = !atty::is(atty::Stream::Stdout);
+        let has_input_pipe   = !atty::is(atty::Stream::Stdin);
+        let input_data       = matches.is_present("input-pipe-data");
+        let output_data      = matches.is_present("output-pipe-data");
+        let blackhole_stdout = matches.is_present("blackhole-stdout");
 
         debug!("has output pipe  = {}", has_output_pipe);
         debug!("has input pipe   = {}", has_input_pipe);
         debug!("input pipe data  = {}", input_data);
         debug!("output pipe data = {}", output_data);
+        debug!("blackhole output = {}", blackhole_stdout);
 
         store_result.map(|store| Runtime {
             cli_matches: matches,
@@ -158,6 +161,7 @@ impl<'a> Runtime<'a> {
             has_input_pipe,
             input_data,
             output_data,
+            blackhole_stdout,
         })
         .context(anyhow!("Cannot instantiate runtime"))
         .map_err(Error::from)
@@ -257,7 +261,22 @@ impl<'a> Runtime<'a> {
                  .takes_value(false)
                  .multiple(false)
                  .help("Do not print imag ids to stdout if stdout is a pipe.")
-                 )
+            )
+
+            .arg(Arg::with_name("blackhole-stdout")
+                 .long("blackhole")
+                 .short("B")
+                 .required(false)
+                 .takes_value(false)
+                 .multiple(false)
+                 .help("Do not print normal output")
+                 .long_help(indoc!(r#"
+                 This flag can be used to ignore output.
+                 For example, if imag is used in a piping context, which pipes the Store IDs, the
+                 normal output is automatically redirected to stderr. To ignore the normal output
+                 instead, this flag can be passed.
+                 "#))
+             )
 
     }
 
@@ -420,6 +439,10 @@ impl<'a> Runtime<'a> {
         self.has_input_pipe
     }
 
+    pub fn output_is_blackholed(&self) -> bool {
+        self.blackhole_stdout
+    }
+
     /// Check whether the runtime expects imag ids from stdin
     pub fn ids_from_stdin(&self) -> bool {
         self.input_is_pipe() && !self.input_data
@@ -438,6 +461,8 @@ impl<'a> Runtime<'a> {
     pub fn stdout(&self) -> OutputProxy {
         if self.output_is_pipe() && self.output_data {
             OutputProxy::Out(::std::io::stdout())
+        } else if self.output_is_blackholed() {
+            OutputProxy::Sink
         } else {
             OutputProxy::Err(::std::io::stderr())
         }
-- 
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