fix: address review feedback and add feature powerset CI

- Make spin a required dependency for no_std hook support (OnceLock unavailable)
- Simplify cfg guards: not(std) instead of not(std) && spin
- Change clippy alloc/std lints from warn to deny
- Remove no_std stub for from_current_location (compile-time vs runtime error)
- Fix is_graphical cfg logic for fancy-base without fancy-no-backtrace
- Add cargo-hack feature powerset CI job to verify all 56 combinations

.github/workflows/ci.yml

@@ -99,6 +99,20 @@ jobs:
           MIRIFLAGS: -Zmiri-disable-isolation -Zmiri-strict-provenance
         run: cargo miri test --all --verbose --features fancy
 
+  feature-check:
+    name: Feature combinations check
+    runs-on: ubuntu-latest
+    steps:
+      - uses: actions/checkout@v4
+      - name: Install Rust
+        uses: dtolnay/rust-toolchain@master
+        with:
+          toolchain: stable
+      - name: Install cargo-hack
+        uses: taiki-e/install-action@cargo-hack
+      - name: Check feature powerset
+        run: cargo hack check --feature-powerset --no-dev-deps --skip default
+
   minimal_versions:
     name: Minimal versions check
     runs-on: ${{ matrix.os }}

Cargo.toml

@@ -16,7 +16,7 @@ exclude = ["images/", "tests/", "miette-derive/"]
 miette-derive = { path = "miette-derive", version = "=7.6.0", optional = true }
 unicode-width = "0.2.0"
 cfg-if = "1.0.0"
-spin = { version = "0.9", default-features = false, features = ["once"], optional = true }
+spin = { version = "0.9", default-features = false, features = ["once"] }
 
 owo-colors = { version = "4.0.0", optional = true }
 textwrap = { version = "0.16.0", default-features = false, features = ["unicode-linebreak", "unicode-width"], optional = true }

src/eyreish/mod.rs

@@ -68,7 +68,7 @@ pub type ErrorHook =
 #[cfg(feature = "std")]
 static HOOK: OnceLock<ErrorHook> = OnceLock::new();
 
-#[cfg(all(not(feature = "std"), feature = "spin"))]
+#[cfg(not(feature = "std"))]
 static HOOK: spin::Once<ErrorHook> = spin::Once::new();
 
 fn default_hook() -> ErrorHook {
@@ -96,7 +96,7 @@ pub fn set_hook(hook: ErrorHook) -> Result<(), InstallError> {
 }
 
 /// Set the error hook.
-#[cfg(all(not(feature = "std"), feature = "spin"))]
+#[cfg(not(feature = "std"))]
 pub fn set_hook(hook: ErrorHook) -> Result<(), InstallError> {
     HOOK.call_once(|| hook);
     Ok(())
@@ -108,7 +108,7 @@ pub(crate) fn capture_handler(error: &(dyn Diagnostic + 'static)) -> Box<dyn Rep
     hook(error)
 }
 
-#[cfg(all(not(feature = "std"), feature = "spin"))]
+#[cfg(not(feature = "std"))]
 pub(crate) fn capture_handler(error: &(dyn Diagnostic + 'static)) -> Box<dyn ReportHandler> {
     let hook = HOOK.call_once(default_hook);
     hook(error)
@@ -126,7 +126,7 @@ pub(crate) fn capture_handler_with_location(
 }
 
 #[track_caller]
-#[cfg(all(not(feature = "std"), feature = "spin"))]
+#[cfg(not(feature = "std"))]
 pub(crate) fn capture_handler_with_location(
     error: &(dyn Diagnostic + 'static),
 ) -> Box<dyn ReportHandler> {

src/handler.rs

@@ -352,10 +352,6 @@ impl MietteHandlerOpts {
         } else if let Some(force_graphical) = self.force_graphical {
             force_graphical
         } else {
-            #[cfg(all(feature = "fancy-no-syscall", not(feature = "fancy-no-backtrace")))]
-            {
-                true
-            }
             #[cfg(feature = "fancy-no-backtrace")]
             {
                 if let Ok(env) = std::env::var("NO_GRAPHICS") {
@@ -364,6 +360,11 @@ impl MietteHandlerOpts {
                     true
                 }
             }
+            #[cfg(not(feature = "fancy-no-backtrace"))]
+            {
+                // fancy-base or fancy-no-syscall without std: default to graphical
+                true
+            }
         }
     }
 

src/lib.rs

@@ -1,7 +1,7 @@
 #![no_std]
 #![deny(missing_docs, missing_debug_implementations, nonstandard_style)]
 #![warn(unreachable_pub, rust_2018_idioms)]
-#![warn(
+#![deny(
     clippy::alloc_instead_of_core,
     clippy::std_instead_of_core,
     clippy::std_instead_of_alloc

src/protocol.rs

@@ -731,15 +731,6 @@ impl SourceOffset {
                 .map(|txt| Self::from_location(txt, loc.line() as usize, loc.column() as usize))?,
         ))
     }
-
-    /// Returns both the filename that was given and the offset of the caller
-    /// as a [`SourceOffset`].
-    ///
-    /// In no_std environments, this is not supported and will return an error.
-    #[cfg(not(feature = "std"))]
-    pub fn from_current_location() -> Result<(String, Self), MietteError> {
-        Err(MietteError::OutOfBounds)
-    }
 }
 
 impl From<ByteOffset> for SourceOffset {