diff options
Diffstat (limited to 'tvix/eval/src/value/mod.rs')
| -rw-r--r-- | tvix/eval/src/value/mod.rs | 186 |
1 files changed, 103 insertions, 83 deletions
diff --git a/tvix/eval/src/value/mod.rs b/tvix/eval/src/value/mod.rs index 596dddba520b..003567bfd440 100644 --- a/tvix/eval/src/value/mod.rs +++ b/tvix/eval/src/value/mod.rs @@ -289,102 +289,122 @@ impl Value { } } - // TODO(amjoseph): de-asyncify this (when called directly by the VM) + pub async fn coerce_to_string( + self, + co: GenCo, + kind: CoercionKind, + span: LightSpan, + ) -> Result<Value, ErrorKind> { + self.coerce_to_string_(&co, kind, span).await + } + /// Coerce a `Value` to a string. See `CoercionKind` for a rundown of what /// input types are accepted under what circumstances. - pub async fn coerce_to_string(self, co: GenCo, kind: CoercionKind) -> Result<Value, ErrorKind> { - let value = generators::request_force(&co, self).await; - - match (value, kind) { - // coercions that are always done - tuple @ (Value::String(_), _) => Ok(tuple.0), - - // TODO(sterni): Think about proper encoding handling here. This needs - // general consideration anyways, since one current discrepancy between - // C++ Nix and Tvix is that the former's strings are arbitrary byte - // sequences without NUL bytes, whereas Tvix only allows valid - // Unicode. See also b/189. - (Value::Path(p), _) => { - // TODO(tazjin): there are cases where coerce_to_string does not import - let imported = generators::request_path_import(&co, *p).await; - Ok(imported.to_string_lossy().into_owned().into()) - } - - // Attribute sets can be converted to strings if they either have an - // `__toString` attribute which holds a function that receives the - // set itself or an `outPath` attribute which should be a string. - // `__toString` is preferred. - (Value::Attrs(attrs), kind) => { - if let Some(s) = attrs.try_to_string(&co, kind).await { - return Ok(Value::String(s)); + pub async fn coerce_to_string_( + self, + co: &GenCo, + kind: CoercionKind, + span: LightSpan, + ) -> Result<Value, ErrorKind> { + let mut result = String::new(); + let mut vals = vec![self]; + loop { + let value = if let Some(v) = vals.pop() { + v.force(co, span.clone()).await? + } else { + return Ok(Value::String(result.into())); + }; + let coerced = match (value, kind) { + // coercions that are always done + (Value::String(s), _) => Ok(s.as_str().to_owned()), + + // TODO(sterni): Think about proper encoding handling here. This needs + // general consideration anyways, since one current discrepancy between + // C++ Nix and Tvix is that the former's strings are arbitrary byte + // sequences without NUL bytes, whereas Tvix only allows valid + // Unicode. See also b/189. + (Value::Path(p), _) => { + // TODO(tazjin): there are cases where coerce_to_string does not import + let imported = generators::request_path_import(co, *p).await; + Ok(imported.to_string_lossy().into_owned()) } - if let Some(out_path) = attrs.select("outPath") { - return match generators::request_string_coerce(&co, out_path.clone(), kind) - .await - { - Ok(s) => Ok(Value::String(s)), - Err(c) => Ok(Value::Catchable(c)), - }; + // Attribute sets can be converted to strings if they either have an + // `__toString` attribute which holds a function that receives the + // set itself or an `outPath` attribute which should be a string. + // `__toString` is preferred. + (Value::Attrs(attrs), kind) => { + if let Some(to_string) = attrs.select("__toString") { + let callable = to_string.clone().force(co, span.clone()).await?; + + // Leave the attribute set on the stack as an argument + // to the function call. + generators::request_stack_push(co, Value::Attrs(attrs.clone())).await; + + // Call the callable ... + let result = generators::request_call(co, callable).await; + + // Recurse on the result, as attribute set coercion + // actually works recursively, e.g. you can even return + // /another/ set with a __toString attr. + vals.push(result); + continue; + } else if let Some(out_path) = attrs.select("outPath") { + vals.push(out_path.clone()); + continue; + } else { + return Err(ErrorKind::NotCoercibleToString { from: "set", kind }); + } } - Err(ErrorKind::NotCoercibleToString { from: "set", kind }) - } - - // strong coercions - (Value::Null, CoercionKind::Strong) | (Value::Bool(false), CoercionKind::Strong) => { - Ok("".into()) - } - (Value::Bool(true), CoercionKind::Strong) => Ok("1".into()), - - (Value::Integer(i), CoercionKind::Strong) => Ok(format!("{i}").into()), - (Value::Float(f), CoercionKind::Strong) => { - // contrary to normal Display, coercing a float to a string will - // result in unconditional 6 decimal places - Ok(format!("{:.6}", f).into()) - } - - // Lists are coerced by coercing their elements and interspersing spaces - (Value::List(list), CoercionKind::Strong) => { - let mut out = String::new(); + // strong coercions + (Value::Null, CoercionKind::Strong) + | (Value::Bool(false), CoercionKind::Strong) => Ok("".to_owned()), + (Value::Bool(true), CoercionKind::Strong) => Ok("1".to_owned()), - for (idx, elem) in list.into_iter().enumerate() { - if idx > 0 { - out.push(' '); - } + (Value::Integer(i), CoercionKind::Strong) => Ok(format!("{i}")), + (Value::Float(f), CoercionKind::Strong) => { + // contrary to normal Display, coercing a float to a string will + // result in unconditional 6 decimal places + Ok(format!("{:.6}", f)) + } - match generators::request_string_coerce(&co, elem, kind).await { - Ok(s) => out.push_str(s.as_str()), - Err(c) => return Ok(Value::Catchable(c)), + // Lists are coerced by coercing their elements and interspersing spaces + (Value::List(list), CoercionKind::Strong) => { + for elem in list.into_iter().rev() { + vals.push(elem); } + continue; } - Ok(Value::String(out.into())) - } + (Value::Thunk(_), _) => panic!("Tvix bug: force returned unforced thunk"), + + val @ (Value::Closure(_), _) + | val @ (Value::Builtin(_), _) + | val @ (Value::Null, _) + | val @ (Value::Bool(_), _) + | val @ (Value::Integer(_), _) + | val @ (Value::Float(_), _) + | val @ (Value::List(_), _) => Err(ErrorKind::NotCoercibleToString { + from: val.0.type_of(), + kind, + }), - (Value::Thunk(_), _) => panic!("Tvix bug: force returned unforced thunk"), - - val @ (Value::Closure(_), _) - | val @ (Value::Builtin(_), _) - | val @ (Value::Null, _) - | val @ (Value::Bool(_), _) - | val @ (Value::Integer(_), _) - | val @ (Value::Float(_), _) - | val @ (Value::List(_), _) => Err(ErrorKind::NotCoercibleToString { - from: val.0.type_of(), - kind, - }), - - (c @ Value::Catchable(_), _) => Ok(c), - - (Value::AttrNotFound, _) - | (Value::Blueprint(_), _) - | (Value::DeferredUpvalue(_), _) - | (Value::UnresolvedPath(_), _) - | (Value::Json(_), _) - | (Value::FinaliseRequest(_), _) => { - panic!("tvix bug: .coerce_to_string() called on internal value") + (c @ Value::Catchable(_), _) => return Ok(c), + + (Value::AttrNotFound, _) + | (Value::Blueprint(_), _) + | (Value::DeferredUpvalue(_), _) + | (Value::UnresolvedPath(_), _) + | (Value::Json(_), _) + | (Value::FinaliseRequest(_), _) => { + panic!("tvix bug: .coerce_to_string() called on internal value") + } + }; + if !result.is_empty() { + result.push(' '); } + result.push_str(&coerced?); } } |