wiggle: add config options for logging

crates/wiggle/generate/src/config.rs

@@ -18,6 +18,7 @@ pub struct Config {
     pub witx: WitxConf,
     pub ctx: CtxConf,
     pub errors: ErrorConf,
+    pub logging: LoggingConf,
 }
 
 #[derive(Debug, Clone)]
@@ -25,25 +26,45 @@ pub enum ConfigField {
     Witx(WitxConf),
     Ctx(CtxConf),
     Error(ErrorConf),
+    Logging(LoggingConf),
 }
 
-impl ConfigField {
-    pub fn parse_pair(ident: &str, value: ParseStream, err_loc: Span) -> Result<Self> {
-        match ident {
-            "witx" => Ok(ConfigField::Witx(WitxConf::Paths(value.parse()?))),
-            "witx_literal" => Ok(ConfigField::Witx(WitxConf::Literal(value.parse()?))),
-            "ctx" => Ok(ConfigField::Ctx(value.parse()?)),
-            "errors" => Ok(ConfigField::Error(value.parse()?)),
-            _ => Err(Error::new(err_loc, "expected `witx`, `ctx`, or `errors`")),
-        }
-    }
+mod kw {
+    syn::custom_keyword!(witx);
+    syn::custom_keyword!(witx_literal);
+    syn::custom_keyword!(ctx);
+    syn::custom_keyword!(logging);
+    syn::custom_keyword!(errors);
+    syn::custom_keyword!(log);
+    syn::custom_keyword!(tracing);
 }
 
 impl Parse for ConfigField {
     fn parse(input: ParseStream) -> Result<Self> {
-        let id: Ident = input.parse()?;
-        let _colon: Token![:] = input.parse()?;
-        Self::parse_pair(id.to_string().as_ref(), input, id.span())
+        let lookahead = input.lookahead1();
+        if lookahead.peek(kw::witx) {
+            input.parse::<kw::witx>()?;
+            input.parse::<Token![:]>()?;
+            Ok(ConfigField::Witx(WitxConf::Paths(input.parse()?)))
+        } else if lookahead.peek(kw::witx_literal) {
+            input.parse::<kw::witx_literal>()?;
+            input.parse::<Token![:]>()?;
+            Ok(ConfigField::Witx(WitxConf::Literal(input.parse()?)))
+        } else if lookahead.peek(kw::ctx) {
+            input.parse::<kw::ctx>()?;
+            input.parse::<Token![:]>()?;
+            Ok(ConfigField::Ctx(input.parse()?))
+        } else if lookahead.peek(kw::logging) {
+            input.parse::<kw::logging>()?;
+            input.parse::<Token![:]>()?;
+            Ok(ConfigField::Logging(input.parse()?))
+        } else if lookahead.peek(kw::errors) {
+            input.parse::<kw::errors>()?;
+            input.parse::<Token![:]>()?;
+            Ok(ConfigField::Error(input.parse()?))
+        } else {
+            Err(lookahead.error())
+        }
     }
 }
 
@@ -52,6 +73,7 @@ impl Config {
         let mut witx = None;
         let mut ctx = None;
         let mut errors = None;
+        let mut logging = None;
         for f in fields {
             match f {
                 ConfigField::Witx(c) => {
@@ -72,6 +94,12 @@ impl Config {
                     }
                     errors = Some(c);
                 }
+                ConfigField::Logging(c) => {
+                    if logging.is_some() {
+                        return Err(Error::new(err_loc, "duplicate `logging` field"));
+                    }
+                    logging = Some(c);
+                }
             }
         }
         Ok(Config {
@@ -82,6 +110,7 @@ impl Config {
                 .take()
                 .ok_or_else(|| Error::new(err_loc, "`ctx` field required"))?,
             errors: errors.take().unwrap_or_default(),
+            logging: logging.take().unwrap_or_default(),
         })
     }
 
@@ -290,3 +319,34 @@ impl Parse for ErrorConfField {
         })
     }
 }
+
+/// Configure logging statements in generated code
+pub enum LoggingConf {
+    Log { cfg_feature: Option<String> },
+    Tracing,
+}
+
+impl Default for LoggingConf {
+    fn default() -> Self {
+        // For compatibility with existing code. We should probably revise this later.
+        LoggingConf::Log {
+            cfg_feature: Some("trace_log".to_owned()),
+        }
+    }
+}
+
+impl Parse for LoggingConf {
+    fn parse(input: ParseStream) -> Result<Self> {
+        let lookahead = input.lookahead1();
+        if lookahead.peek(kw::log) {
+            input.parse::<kw::log>()?;
+            // TODO: syntax so the user can specify their own cfg_feature guard here.
+            Ok(LoggingConf::Log { cfg_feature: None })
+        } else if lookahead.peek(kw::tracing) {
+            input.parse::<kw::tracing>()?;
+            Ok(LoggingConf::Tracing)
+        } else {
+            Err(lookahead.error())
+        }
+    }
+}