refactor!: use cfg(nightly) instead of feature, remove -Z flag, u…

…se `Diagnostic::try_emit` (#1606)

Previous PR (#1587) website build did not work because `panic = "abort"`
is set on wasm, leading to aborts for `proc_macro2::Span::unwrap()`
calls.

All tests except trybuild seem to pass on stable, WIP #1587 next

BREAKING CHANGE: replaces `hydroflow_lang::diagnostic::Diagnostic::emit`
with `try_emit`
BREAKING CHANGE: removes features: `hydroflow/nightly`,
`hydroflow_datalog/diagnostics`, `hydroflow_datalog_core/diagnostics`,
`hydroflow_lang/diagnostics`, `hydroflow_macro/diagnostics`,
`hydroflow_plus/diagnostics`.

.cargo/config.toml

@@ -1,12 +1,8 @@
 [build]
 rustflags = [
-    "-Zproc-macro-backtrace",
     # Flag to make build.rs scripts generate docs. Should only be used in this repository
     # internally, not by dependants.
     '--cfg=HYDROFLOW_GENERATE_DOCS',
-    # https://github.com/rust-lang/rust-clippy/issues/10087
-    ## TODO(mingwei): Need rust-analyzer support:
-    # "-Aclippy::uninlined-format-args",
 ]
 
 [target.x86_64-apple-darwin]

hydroflow/Cargo.toml

@@ -11,9 +11,8 @@ description = "Hydro's low-level dataflow runtime and IR"
 workspace = true
 
 [features]
-default = [ "macros", "nightly", "debugging" ]
+default = [ "macros", "debugging" ]
 
-nightly = [ "hydroflow_macro", "hydroflow_macro/diagnostics" ]
 macros = [ "hydroflow_macro", "hydroflow_datalog" ]
 hydroflow_macro = [ "dep:hydroflow_macro" ]
 hydroflow_datalog = [ "dep:hydroflow_datalog" ]

hydroflow/src/lib.rs

@@ -1,4 +1,3 @@
-#![cfg_attr(feature = "nightly", feature(never_type))]
 #![warn(missing_docs)]
 
 //! Hydroflow is a low-level dataflow-based runtime system for the [Hydro Project](https://hydro.run/).
@@ -39,12 +38,9 @@ pub use hydroflow_macro::{
     hydroflow_test as test, monotonic_fn, morphism, DemuxEnum,
 };
 
+// TODO(mingwei): Use the [nightly "never" type `!`](https://doc.rust-lang.org/std/primitive.never.html)
 /// Stand-in for the [nightly "never" type `!`](https://doc.rust-lang.org/std/primitive.never.html)
-#[cfg(not(feature = "nightly"))]
 pub type Never = std::convert::Infallible;
-/// The [nightly "never" type `!`](https://doc.rust-lang.org/std/primitive.never.html)
-#[cfg(feature = "nightly")]
-pub type Never = !;
 
 #[cfg(doctest)]
 mod booktest {

hydroflow_datalog/Cargo.toml

@@ -14,9 +14,6 @@ workspace = true
 proc-macro = true
 path = "src/lib.rs"
 
-[features]
-diagnostics = [ "hydroflow_datalog_core/diagnostics" ]
-
 [dependencies]
 quote = "1.0.35"
 syn = { version = "2.0.46", features = [ "parsing", "extra-traits" ] }

hydroflow_datalog/src/lib.rs

@@ -1,3 +1,4 @@
+use hydroflow_datalog_core::diagnostic::Diagnostic;
 use hydroflow_datalog_core::{gen_hydroflow_graph, hydroflow_graph_to_program};
 use proc_macro2::Span;
 use quote::{quote, ToTokens};
@@ -31,10 +32,15 @@ pub fn datalog(item: proc_macro::TokenStream) -> proc_macro::TokenStream {
             program.to_token_stream().into()
         }
         Err(diagnostics) => {
-            for diagnostic in diagnostics {
-                diagnostic.emit();
-            }
-            proc_macro::TokenStream::from(quote!(hydroflow::scheduled::graph::Hydroflow::new()))
+            let diagnostic_tokens = Diagnostic::try_emit_all(diagnostics.iter())
+                .err()
+                .unwrap_or_default();
+            proc_macro::TokenStream::from(quote! {
+                {
+                    #diagnostic_tokens
+                    hydroflow::scheduled::graph::Hydroflow::new()
+                }
+            })
         }
     }
 }

hydroflow_datalog_core/Cargo.toml

@@ -13,10 +13,6 @@ workspace = true
 [lib]
 path = "src/lib.rs"
 
-[features]
-default = []
-diagnostics = [ "hydroflow_lang/diagnostics" ]
-
 [dependencies]
 quote = "1.0.35"
 slotmap = "1.0.0"

hydroflow_datalog_core/src/lib.rs

@@ -1,6 +1,7 @@
 use std::collections::{HashMap, HashSet};
 use std::ops::Deref;
 
+pub use hydroflow_lang::diagnostic;
 use hydroflow_lang::diagnostic::{Diagnostic, Level};
 use hydroflow_lang::graph::{
     eliminate_extra_unions_tees, partition_graph, FlatGraphBuilder, HydroflowGraph,

hydroflow_lang/Cargo.toml

@@ -12,7 +12,6 @@ workspace = true
 
 [features]
 default = []
-diagnostics = []
 debugging = [ "dep:data-encoding", "dep:webbrowser", "clap-derive" ]
 clap-derive = [ "dep:clap" ]
 
@@ -34,3 +33,4 @@ webbrowser = { version = "1.0.0", optional = true }
 
 [build-dependencies]
 syn = { version = "2.0.46", features = [ "extra-traits", "full", "parsing" ] }
+rustc_version = "0.4.0"

hydroflow_lang/build.rs

@@ -4,6 +4,7 @@ use std::fs::File;
 use std::io::{BufWriter, Error, ErrorKind, Result, Write};
 use std::path::PathBuf;
 
+use rustc_version::{version_meta, Channel};
 use syn::{
     parse_quote, AttrStyle, Expr, ExprLit, Ident, Item, Lit, Member, Meta, MetaNameValue, Path,
 };
@@ -12,6 +13,15 @@ const OPS_PATH: &str = "src/graph/ops";
 
 fn main() {
     println!("cargo::rerun-if-changed={}", OPS_PATH);
+
+    println!("cargo::rustc-check-cfg=cfg(nightly)");
+    if matches!(
+        version_meta().map(|meta| meta.channel),
+        Ok(Channel::Nightly)
+    ) {
+        println!("cargo:rustc-cfg=nightly");
+    }
+
     if Err(VarError::NotPresent) != var("CARGO_CFG_HYDROFLOW_GENERATE_DOCS") {
         if let Err(err) = generate_op_docs() {
             eprintln!("hydroflow_lang/build.rs error: {:?}", err);

hydroflow_lang/src/diagnostic.rs

@@ -1,5 +1,7 @@
 //! Compatibility for `proc_macro` diagnostics, which are missing from [`proc_macro2`].
 
+extern crate proc_macro;
+
 use std::borrow::Cow;
 use std::hash::{Hash, Hasher};
 
@@ -40,8 +42,8 @@ impl Level {
 /// Diagnostic. A warning or error (or lower [`Level`]) with a message and span. Shown by IDEs
 /// usually as a squiggly red or yellow underline.
 ///
-/// Must call [`Diagnostic::emit`] or manually emit the output of [`Diagnostic::to_tokens`] for the
-/// diagnostic to show up.
+/// Diagnostics must be emitted via [`Diagnostic::try_emit`], [`Diagnostic::to_tokens`], or
+/// [`Diagnostic::try_emit_all`] for diagnostics to show up.
 #[derive(Debug, Clone, Serialize, Deserialize)]
 pub struct Diagnostic<S = Span> {
     /// Span (source code location).
@@ -68,23 +70,44 @@ impl Diagnostic {
         }
     }
 
-    /// Emit the diagnostic. Only works from the `proc_macro` context. Does not work outside of
-    /// that e.g. in normal runtime execution or in tests.
-    pub fn emit(&self) {
-        #[cfg(feature = "diagnostics")]
-        {
+    /// Emit if possible, otherwise return `Err` containing a [`TokenStream`] of a
+    /// `compile_error!(...)` call.
+    pub fn try_emit(&self) -> Result<(), TokenStream> {
+        #[cfg(nightly)]
+        if proc_macro::is_available() {
             let pm_diag = match self.level {
                 Level::Error => self.span.unwrap().error(&*self.message),
                 Level::Warning => self.span.unwrap().warning(&*self.message),
                 Level::Note => self.span.unwrap().note(&*self.message),
                 Level::Help => self.span.unwrap().help(&*self.message),
             };
             pm_diag.emit();
+            return Ok(());
         }
+        Err(self.to_tokens())
     }
 
-    /// Used to emulate [`Diagnostic::emit`] by turning this diagnostic into a properly spanned [`TokenStream`]
-    /// that emits an error with this diagnostic's message.
+    /// Emits all if possible, otherwise returns `Err` containing a [`TokenStream`] of
+    /// `compile_error!(...)` calls.
+    pub fn try_emit_all<'a>(
+        diagnostics: impl IntoIterator<Item = &'a Self>,
+    ) -> Result<(), TokenStream> {
+        if let Some(tokens) = diagnostics
+            .into_iter()
+            .filter_map(|diag| diag.try_emit().err())
+            .reduce(|mut tokens, next| {
+                tokens.extend(next);
+                tokens
+            })
+        {
+            Err(tokens)
+        } else {
+            Ok(())
+        }
+    }
+
+    /// Used to emulate `proc_macro::Diagnostic::emit` by turning this diagnostic into a properly spanned [`TokenStream`]
+    /// that emits an error via `compile_error!(...)` with this diagnostic's message.
     pub fn to_tokens(&self) -> TokenStream {
         let msg_lit: Literal = Literal::string(&self.message);
         let unique_ident = {
@@ -98,7 +121,7 @@ impl Diagnostic {
         if Level::Error == self.level {
             quote_spanned! {self.span=>
                 {
-                    ::std::compile_error!(#msg_lit);
+                    ::core::compile_error!(#msg_lit);
                 }
             }
         } else {
@@ -169,17 +192,20 @@ pub struct SerdeSpan {
 }
 impl From<Span> for SerdeSpan {
     fn from(span: Span) -> Self {
-        #[cfg(feature = "diagnostics")]
-        let path = span
-            .unwrap()
-            .source_file()
-            .path()
-            .display()
-            .to_string()
-            .into();
+        let path = 'a: {
+            #[cfg(nightly)]
+            if proc_macro::is_available() {
+                break 'a span
+                    .unwrap()
+                    .source_file()
+                    .path()
+                    .display()
+                    .to_string()
+                    .into();
+            }
 
-        #[cfg(not(feature = "diagnostics"))]
-        let path = "unknown".into();
+            break 'a "unknown".into();
+        };
 
         Self {
             path,

hydroflow_lang/src/graph/hydroflow_graph.rs

@@ -1,5 +1,7 @@
 #![warn(missing_docs)]
 
+extern crate proc_macro;
+
 use std::collections::{BTreeMap, BTreeSet};
 use std::fmt::Debug;
 use std::iter::FusedIterator;
@@ -1006,13 +1008,11 @@ impl HydroflowGraph {
                             subgraph_op_iter_code.push(write_iterator);
 
                             if include_type_guards {
-                                #[cfg(not(feature = "diagnostics"))]
-                                let source_info = Option::<String>::None;
-
-                                #[cfg(feature = "diagnostics")]
-                                let source_info = std::panic::catch_unwind(|| op_span.unwrap())
-                                    .map(|op_span| {
-                                        format!(
+                                let source_info = 'a: {
+                                    #[cfg(nightly)]
+                                    if proc_macro::is_available() {
+                                        let op_span = op_span.unwrap();
+                                        break 'a format!(
                                             "loc_{}_{}_{}_{}_{}",
                                             op_span
                                                 .source_file()
@@ -1024,26 +1024,17 @@ impl HydroflowGraph {
                                             op_span.start().column(),
                                             op_span.end().line(),
                                             op_span.end().column(),
-                                        )
-                                    })
-                                    .ok();
-
-                                #[cfg_attr(
-                                    not(feature = "diagnostics"),
-                                    expect(
-                                        clippy::unnecessary_literal_unwrap,
-                                        reason = "conditional compilation"
-                                    )
-                                )]
-                                let source_info = source_info.unwrap_or_else(|| {
-                                    format!(
+                                        );
+                                    }
+
+                                    break 'a format!(
                                         "loc_nopath_{}_{}_{}_{}",
                                         op_span.start().line,
                                         op_span.start().column,
                                         op_span.end().line,
                                         op_span.end().column
-                                    )
-                                });
+                                    );
+                                };
 
                                 let fn_ident = format_ident!(
                                     "{}__{}__{}",

hydroflow_lang/src/lib.rs

@@ -1,10 +1,7 @@
 //! Hydroflow surface syntax
 
 #![warn(missing_docs)]
-#![cfg_attr(
-    feature = "diagnostics",
-    feature(proc_macro_diagnostic, proc_macro_span)
-)]
+#![cfg_attr(nightly, feature(proc_macro_diagnostic, proc_macro_span))]
 pub mod diagnostic;
 pub mod graph;
 pub mod parse;

hydroflow_lang/src/pretty_span.rs

@@ -1,27 +1,28 @@
 //! Pretty, human-readable printing of [`proc_macro2::Span`]s.
 
+extern crate proc_macro;
+
 /// Helper struct which displays the span as `path:row:col` for human reading/IDE linking.
 /// Example: `hydroflow\tests\surface_syntax.rs:42:18`.
 pub struct PrettySpan(pub proc_macro2::Span);
 impl std::fmt::Display for PrettySpan {
     fn fmt(&self, f: &mut std::fmt::Formatter<'_>) -> std::fmt::Result {
-        #[cfg(feature = "diagnostics")]
-        {
-            if let Ok(span) = std::panic::catch_unwind(|| self.0.unwrap()) {
-                write!(
-                    f,
-                    "{}:{}:{}",
-                    span.source_file().path().display(),
-                    span.start().line(),
-                    span.start().column(),
-                )?;
-                return Ok(());
-            }
+        #[cfg(nightly)]
+        if proc_macro::is_available() {
+            let span = self.0.unwrap();
+            write!(
+                f,
+                "{}:{}:{}",
+                span.source_file().path().display(),
+                span.start().line(),
+                span.start().column(),
+            )?;
+            return Ok(());
         }
 
         write!(
             f,
-            "nopath:{}:{}",
+            "unknown:{}:{}",
             self.0.start().line,
             self.0.start().column
         )