first feed the input, then read its output

src/formatters/custom.rs

@@ -1,7 +1,6 @@
-use std::io::Write;
 use std::path::PathBuf;
 use std::process::{Command, Stdio};
-use std::io::Read;
+use std::io::{Read, Write};
 
 use csv::Writer;
 use chrono::SecondsFormat;
@@ -64,7 +63,6 @@ where
     })?;
 
     let config = get_formatter_config(&facts.config, formatter);
-
     let mut command = Command::new(&path);
 
     command
@@ -74,35 +72,40 @@ where
         .stderr(Stdio::piped());
 
     let mut child = command.spawn().map_err(|e| CustomFormatterFailed(path, e))?;
-
     let stdin = child.stdin.take().expect("Failed to take stdin");
     let mut stdout = child.stdout.take().expect("Failed to take stdout");
     let mut stderr = child.stderr.take().expect("Failed to take stdout");
 
-    let mut wtr = Writer::from_writer(stdin);
+    {
+        let mut wtr = Writer::from_writer(stdin);
+
+        for entry in entries {
+            // write to process' stdin
+            wtr.write_record(&[
+                entry.id.to_string(),
+                entry.start.to_rfc3339_opts(SecondsFormat::Micros, true),
+                entry.end.map(|t| t.to_rfc3339_opts(SecondsFormat::Micros, true)).unwrap_or_else(|| "".into()),
+                entry.note.unwrap_or_else(|| "".into()),
+                entry.sheet,
+            ])?;
+        }
+    }
+
+    // All the input has been fed to the child process, now we wait for it to
+    // finish and then read its output
+    child.wait()?;
+
     let mut captured_out = String::new();
     let mut captured_err = String::new();
 
-    for entry in entries {
-        // write to process' stdin
-        wtr.write_record(&[
-            entry.id.to_string(),
-            entry.start.to_rfc3339_opts(SecondsFormat::Micros, true),
-            entry.end.map(|t| t.to_rfc3339_opts(SecondsFormat::Micros, true)).unwrap_or_else(|| "".into()),
-            entry.note.unwrap_or_else(|| "".into()),
-            entry.sheet,
-        ])?;
-        wtr.flush()?;
+    // read process' stdout and stderr
+    stdout.read_to_string(&mut captured_out)?;
+    write!(out, "{}", &captured_out)?;
+    captured_out.clear();
 
-        // read process' stdout and stderr
-        stdout.read_to_string(&mut captured_out)?;
-        write!(out, "{}", &captured_out)?;
-        captured_out.clear();
-
-        stderr.read_to_string(&mut captured_err)?;
-        write!(err, "{}", &captured_err)?;
-        captured_err.clear();
-    }
+    stderr.read_to_string(&mut captured_err)?;
+    write!(err, "{}", &captured_err)?;
+    captured_err.clear();
 
     Ok(())
 }
@@ -122,8 +125,7 @@ mod tests {
 
         assert_eq!(err.to_string(), "\
 The specified name for a custom formatter \"pol/lo\" is not valid. Only ascii
-letters, numbers, dots, dashes and underscores are allowed.
-");
+letters, numbers, dots, dashes and underscores are allowed.");
     }
 
     #[test]
@@ -139,8 +141,7 @@ where to look for it.
 
 You can set a path using
 
-t config --formatter-search-paths <path>..
-");
+t config --formatter-search-paths <path>..");
     }
 
     #[test]