CLI Tool: Allow using --file - to read metadata from stdin (#1336)

* allow using --file - to read from stdin

* add test for path and url parsing

---------

Co-authored-by: James Wilson <james@jsdw.me>

cli/src/utils.rs

@@ -21,7 +21,7 @@ pub struct FileOrUrl {
     pub url: Option<Url>,
     /// The path to the encoded metadata file.
     #[clap(long, value_parser)]
-    pub file: Option<PathBuf>,
+    pub file: Option<PathOrStdIn>,
     /// Specify the metadata version.
     ///
     ///  - "latest": Use the latest stable version available.
@@ -33,6 +33,54 @@ pub struct FileOrUrl {
     pub version: Option<MetadataVersion>,
 }
 
+impl FromStr for FileOrUrl {
+    type Err = &'static str;
+
+    fn from_str(s: &str) -> Result<Self, Self::Err> {
+        if let Ok(path) = PathOrStdIn::from_str(s) {
+            Ok(FileOrUrl {
+                url: None,
+                file: Some(path),
+                version: None,
+            })
+        } else {
+            Url::parse(s)
+                .map_err(|_| "Parsing Path or Uri failed.")
+                .map(|uri| FileOrUrl {
+                    url: Some(uri),
+                    file: None,
+                    version: None,
+                })
+        }
+    }
+}
+
+/// If `--path -` is provided, read bytes for metadata from stdin
+const STDIN_PATH_NAME: &str = "-";
+#[derive(Debug, Clone)]
+pub enum PathOrStdIn {
+    Path(PathBuf),
+    StdIn,
+}
+
+impl FromStr for PathOrStdIn {
+    type Err = &'static str;
+
+    fn from_str(s: &str) -> Result<Self, Self::Err> {
+        let s = s.trim();
+        if s == STDIN_PATH_NAME {
+            Ok(PathOrStdIn::StdIn)
+        } else {
+            let path = std::path::Path::new(s);
+            if path.exists() {
+                Ok(PathOrStdIn::Path(PathBuf::from(path)))
+            } else {
+                Err("Path does not exist.")
+            }
+        }
+    }
+}
+
 impl FileOrUrl {
     /// Fetch the metadata bytes.
     pub async fn fetch(&self) -> color_eyre::Result<Vec<u8>> {
@@ -42,12 +90,20 @@ impl FileOrUrl {
                 eyre::bail!("specify one of `--url` or `--file` but not both")
             }
             // Load from --file path
-            (Some(path), None, None) => {
+            (Some(PathOrStdIn::Path(path)), None, None) => {
                 let mut file = fs::File::open(path)?;
                 let mut bytes = Vec::new();
                 file.read_to_end(&mut bytes)?;
                 Ok(bytes)
             }
+            (Some(PathOrStdIn::StdIn), None, None) => {
+                let res = std::io::stdin().bytes().collect::<Result<Vec<u8>, _>>();
+
+                match res {
+                    Ok(bytes) => Ok(bytes),
+                    Err(err) => eyre::bail!("reading bytes from stdin (`--file -`) failed: {err}"),
+                }
+            }
             // Cannot load the metadata from the file and specify a version to fetch.
             (Some(_), None, Some(_)) => {
                 // Note: we could provide the ability to convert between metadata versions
@@ -88,25 +144,49 @@ pub fn with_indent(s: String, indent: usize) -> String {
         .join("\n")
 }
 
-impl FromStr for FileOrUrl {
-    type Err = &'static str;
+#[cfg(test)]
+mod tests {
+    use crate::utils::{FileOrUrl, PathOrStdIn};
+    use std::str::FromStr;
 
-    fn from_str(s: &str) -> Result<Self, Self::Err> {
-        let path = std::path::Path::new(s);
-        if path.exists() {
+    #[test]
+    fn parsing() {
+        assert!(matches!(
+            FileOrUrl::from_str("-"),
             Ok(FileOrUrl {
                 url: None,
-                file: Some(PathBuf::from(s)),
-                version: None,
+                file: Some(PathOrStdIn::StdIn),
+                version: None
             })
-        } else {
-            Url::parse(s)
-                .map_err(|_| "no path or uri could be crated")
-                .map(|uri| FileOrUrl {
-                    url: Some(uri),
-                    file: None,
-                    version: None,
-                })
-        }
+        ),);
+
+        assert!(matches!(
+            FileOrUrl::from_str("  -  "),
+            Ok(FileOrUrl {
+                url: None,
+                file: Some(PathOrStdIn::StdIn),
+                version: None
+            })
+        ),);
+
+        assert!(matches!(
+            FileOrUrl::from_str("./src/main.rs"),
+            Ok(FileOrUrl {
+                url: None,
+                file: Some(PathOrStdIn::Path(_)),
+                version: None
+            })
+        ),);
+
+        assert!(FileOrUrl::from_str("./src/i_dont_exist.rs").is_err());
+
+        assert!(matches!(
+            FileOrUrl::from_str("https://github.com/paritytech/subxt"),
+            Ok(FileOrUrl {
+                url: Some(_),
+                file: None,
+                version: None
+            })
+        ));
     }
 }