Show full ffmpeg command after errors

CHANGELOG.md

@@ -1,3 +1,6 @@
+# Unreleased
+* Show full ffmpeg command after errors.
+
 # v0.7.14
 * Fix bash completions of some filenames.
 

src/ffmpeg.rs

@@ -85,8 +85,8 @@ pub fn encode_sample(
 
     temporary::add(&dest, TempKind::Keepable);
 
-    let enc = Command::new("ffmpeg")
-        .kill_on_drop(true)
+    let mut cmd = Command::new("ffmpeg");
+    cmd.kill_on_drop(true)
         .arg("-y")
         .args(input_args.iter().map(|a| &**a))
         .arg2("-i", input)
@@ -100,11 +100,12 @@ pub fn encode_sample(
         .arg(&dest)
         .stdin(Stdio::null())
         .stdout(Stdio::null())
-        .stderr(Stdio::piped())
-        .spawn()
-        .context("ffmpeg encode_sample")?;
+        .stderr(Stdio::piped());
+    let cmd_str = cmd.to_cmd_str();
 
-    let stream = FfmpegOut::stream(enc, "ffmpeg encode_sample");
+    let enc = cmd.spawn().context("ffmpeg encode_sample")?;
+
+    let stream = FfmpegOut::stream(enc, "ffmpeg encode_sample", cmd_str);
     Ok((dest, stream))
 }
 
@@ -146,8 +147,8 @@ pub fn encode(
         false => "0",
     };
 
-    let enc = Command::new("ffmpeg")
-        .kill_on_drop(true)
+    let mut cmd = Command::new("ffmpeg");
+    cmd.kill_on_drop(true)
         .args(input_args.iter().map(|a| &**a))
         .arg("-y")
         .arg2("-i", input)
@@ -168,11 +169,12 @@ pub fn encode(
         .arg(output)
         .stdin(Stdio::null())
         .stdout(Stdio::null())
-        .stderr(Stdio::piped())
-        .spawn()
-        .context("ffmpeg encode")?;
+        .stderr(Stdio::piped());
+    let cmd_str = cmd.to_cmd_str();
+
+    let enc = cmd.spawn().context("ffmpeg encode")?;
 
-    Ok(FfmpegOut::stream(enc, "ffmpeg encode"))
+    Ok(FfmpegOut::stream(enc, "ffmpeg encode", cmd_str))
 }
 
 pub fn pre_extension_name(vcodec: &str) -> &str {

src/process.rs

@@ -42,10 +42,15 @@ pub fn exit_ok(name: &'static str, done: io::Result<ExitStatus>) -> anyhow::Resu
 pub fn exit_ok_stderr(
     name: &'static str,
     done: io::Result<ExitStatus>,
+    cmd_str: &str,
     stderr: &Chunks,
 ) -> anyhow::Result<()> {
-    exit_ok(name, done)
-        .map_err(|e| anyhow!("{e}\n---stderr---\n{}\n------------", stderr.out.trim()))
+    exit_ok(name, done).map_err(|e| {
+        anyhow!(
+            "{e}\n----cmd-----\n{cmd_str}\n---stderr---\n{}\n------------",
+            stderr.out.trim()
+        )
+    })
 }
 
 #[derive(Debug, PartialEq)]
@@ -98,6 +103,7 @@ impl FfmpegOut {
     pub fn stream(
         child: Child,
         name: &'static str,
+        cmd_str: String,
     ) -> impl Stream<Item = anyhow::Result<FfmpegOut>> {
         let mut chunks = Chunks::default();
         ProcessChunkStream::from(child).filter_map(move |item| match item {
@@ -106,7 +112,7 @@ impl FfmpegOut {
                 FfmpegOut::try_parse(chunks.last_line()).map(Ok)
             }
             Item::Stdout(_) => None,
-            Item::Done(code) => match exit_ok_stderr(name, code, &chunks) {
+            Item::Done(code) => match exit_ok_stderr(name, code, &cmd_str, &chunks) {
                 Ok(_) => None,
                 Err(err) => Some(Err(err)),
             },
@@ -232,6 +238,9 @@ pub trait CommandExt {
 
     /// Adds two arguments if `condition` otherwise noop.
     fn arg2_if(&mut self, condition: bool, a: impl ArgString, b: impl ArgString) -> &mut Self;
+
+    /// Convert to readable shell-like string.
+    fn to_cmd_str(&self) -> String;
 }
 impl CommandExt for tokio::process::Command {
     fn arg2(&mut self, a: impl ArgString, b: impl ArgString) -> &mut Self {
@@ -251,6 +260,18 @@ impl CommandExt for tokio::process::Command {
             false => self,
         }
     }
+
+    fn to_cmd_str(&self) -> String {
+        let cmd = self.as_std();
+        cmd.get_args().map(|a| a.to_string_lossy()).fold(
+            cmd.get_program().to_string_lossy().to_string(),
+            |mut all, next| {
+                all.push(' ');
+                all += &next;
+                all
+            },
+        )
+    }
 }
 
 pub trait ArgString {

src/vmaf.rs

@@ -13,23 +13,26 @@ pub fn run(
     distorted: &Path,
     filter_complex: &str,
 ) -> anyhow::Result<impl Stream<Item = VmafOut>> {
-    let vmaf: ProcessChunkStream = Command::new("ffmpeg")
-        .kill_on_drop(true)
+    let mut cmd = Command::new("ffmpeg");
+    cmd.kill_on_drop(true)
         .arg2("-r", "24")
         .arg2("-i", distorted)
         .arg2("-r", "24")
         .arg2("-i", reference)
         .arg2("-filter_complex", filter_complex)
         .arg2("-f", "null")
-        .arg("-")
-        .try_into()
-        .context("ffmpeg vmaf")?;
+        .arg("-");
+
+    let cmd_str = cmd.to_cmd_str();
+    let vmaf: ProcessChunkStream = cmd.try_into().context("ffmpeg vmaf")?;
 
     let mut chunks = Chunks::default();
     let vmaf = vmaf.filter_map(move |item| match item {
         Item::Stderr(chunk) => VmafOut::try_from_chunk(&chunk, &mut chunks),
         Item::Stdout(_) => None,
-        Item::Done(code) => VmafOut::ignore_ok(exit_ok_stderr("ffmpeg vmaf", code, &chunks)),
+        Item::Done(code) => {
+            VmafOut::ignore_ok(exit_ok_stderr("ffmpeg vmaf", code, &cmd_str, &chunks))
+        }
     });
 
     Ok(vmaf)