Error printing changes for watch (#5389)

* Move CliError to nu-protocol

clean up comment

* Enable printing errors instead of just returning them

* Nicer Miette error printing in watch command

crates/nu-protocol/src/cli_error.rs

@@ -0,0 +1,61 @@
+use crate::engine::StateWorkingSet;
+use miette::{LabeledSpan, MietteHandler, ReportHandler, Severity, SourceCode};
+use thiserror::Error;
+
+/// This error exists so that we can defer SourceCode handling. It simply
+/// forwards most methods, except for `.source_code()`, which we provide.
+#[derive(Error)]
+#[error("{0}")]
+pub struct CliError<'src>(
+    pub &'src (dyn miette::Diagnostic + Send + Sync + 'static),
+    pub &'src StateWorkingSet<'src>,
+);
+
+pub fn format_error(
+    working_set: &StateWorkingSet,
+    error: &(dyn miette::Diagnostic + Send + Sync + 'static),
+) -> String {
+    return format!("Error: {:?}", CliError(error, working_set));
+}
+
+impl std::fmt::Debug for CliError<'_> {
+    fn fmt(&self, f: &mut std::fmt::Formatter<'_>) -> std::fmt::Result {
+        MietteHandler::default().debug(self, f)?;
+        Ok(())
+    }
+}
+
+impl<'src> miette::Diagnostic for CliError<'src> {
+    fn code<'a>(&'a self) -> Option<Box<dyn std::fmt::Display + 'a>> {
+        self.0.code()
+    }
+
+    fn severity(&self) -> Option<Severity> {
+        self.0.severity()
+    }
+
+    fn help<'a>(&'a self) -> Option<Box<dyn std::fmt::Display + 'a>> {
+        self.0.help()
+    }
+
+    fn url<'a>(&'a self) -> Option<Box<dyn std::fmt::Display + 'a>> {
+        self.0.url()
+    }
+
+    fn labels<'a>(&'a self) -> Option<Box<dyn Iterator<Item = LabeledSpan> + 'a>> {
+        self.0.labels()
+    }
+
+    // Finally, we redirect the source_code method to our own source.
+    fn source_code(&self) -> Option<&dyn SourceCode> {
+        if let Some(source_code) = self.0.source_code() {
+            Some(source_code)
+        } else {
+            Some(&self.1)
+        }
+    }
+
+    fn related<'a>(&'a self) -> Option<Box<dyn Iterator<Item = &'a dyn miette::Diagnostic> + 'a>> {
+        self.0.related()
+    }
+}

crates/nu-protocol/src/lib.rs

@@ -1,4 +1,5 @@
 pub mod ast;
+mod cli_error;
 mod config;
 pub mod engine;
 mod example;
@@ -14,6 +15,7 @@ mod ty;
 mod value;
 mod variable;
 
+pub use cli_error::*;
 pub use config::*;
 pub use engine::{ENV_VARIABLE_ID, IN_VARIABLE_ID, NU_VARIABLE_ID};
 pub use example::*;

crates/nu-protocol/src/pipeline_data.rs

@@ -455,11 +455,6 @@ impl PipelineData {
 
                 for item in table {
                     let stdout = std::io::stdout();
-
-                    if let Value::Error { error } = item {
-                        return Err(error);
-                    }
-
                     let mut out = item.into_string("\n", config);
                     out.push('\n');
 
@@ -472,11 +467,6 @@ impl PipelineData {
             None => {
                 for item in self {
                     let stdout = std::io::stdout();
-
-                    if let Value::Error { error } = item {
-                        return Err(error);
-                    }
-
                     let mut out = item.into_string("\n", config);
                     out.push('\n');