refactor: allow multiple footers in error/warning messages

With this change we open the possibility of adding multiple footers to error messages.

go/compiler.go

@@ -121,6 +121,8 @@ type CompileError struct {
 	Title string `json:"title"`
 	// Each of the labels in the error report.
 	Labels []Label `json:"labels"`
+	// Each of the footers in the error report.
+	Footers []Footer `json:"footers"`
 	// The error's full report, as shown by the command-line tool.
 	Text string `json:"text"`
 }
@@ -131,8 +133,10 @@ type Warning struct {
 	Code string `json:"code"`
 	// Error title (e.g: "slow pattern").
 	Title string `json:"title"`
-	// Each of the labels in the error report.
+	// Each of the labels in the warning report.
 	Labels []Label `json:"labels"`
+	// Each of the footers in the warning report.
+	Footers []Footer `json:"footers"`
 	// The error's full report, as shown by the command-line tool.
 	Text string `json:"text"`
 }
@@ -149,6 +153,14 @@ type Label struct {
 	Text string `json:"text"`
 }
 
+// Footer represents a footer in a [CompileError].
+type Footer struct {
+	// Footer's level (e.g: "error", "warning", "info", "note", "help").
+	Level string `json:"level"`
+	// Footer's text.
+	Text string `json:"text"`
+}
+
 // Span represents the starting and ending point of some piece of source
 // code.
 type Span struct {

go/compiler_test.go

@@ -131,6 +131,33 @@ func TestErrors(t *testing.T) {
 	c.AddSource("rule test_1 { condition: true }")
 	assert.Equal(t, []CompileError{}, c.Errors())
 
+	assert.Equal(t, []Warning{
+		{
+			Code:  "invariant_expr",
+			Title: "invariant boolean expression",
+			Labels: []Label{
+				{
+					Level: "warning",
+					Span:  Span{Start: 25, End: 29},
+					Text:  "this expression is always true",
+				},
+			},
+			Footers: []Footer{
+				{
+					Level: "note",
+					Text:  "rule `test_1` is always `true`",
+				},
+			},
+			Text: `warning[invariant_expr]: invariant boolean expression
+ --> line:1:26
+  |
+1 | rule test_1 { condition: true }
+  |                          ---- this expression is always true
+  |
+  = note: rule ` + "`test_1` is always `true`",
+		},
+	}, c.Warnings())
+
 	c.AddSource("rule test_2 { condition: foo }", WithOrigin("test.yar"))
 	assert.Equal(t, []CompileError{
 		{
@@ -144,6 +171,7 @@ func TestErrors(t *testing.T) {
 					Text:       "this identifier has not been declared",
 				},
 			},
+			Footers: []Footer{},
 			Text: `error[E009]: unknown identifier ` + "`foo`" + `
  --> test.yar:1:26
   |
@@ -241,6 +269,7 @@ func TestWarnings(t *testing.T) {
 					Text:       "these consecutive jumps will be treated as [0-2]",
 				},
 			},
+			Footers: []Footer{},
 			Text: `warning[consecutive_jumps]: consecutive jumps in hex pattern ` + "`$a`" + `
  --> line:1:31
   |
@@ -259,6 +288,7 @@ func TestWarnings(t *testing.T) {
 					Text:       "this pattern may slow down the scan",
 				},
 			},
+			Footers: []Footer{},
 			Text: `warning[slow_pattern]: slow pattern
  --> line:1:22
   |

lib/src/compiler/errors.rs

@@ -10,7 +10,7 @@ use yara_x_macros::ErrorEnum;
 use yara_x_macros::ErrorStruct;
 use yara_x_parser::ast;
 
-use crate::compiler::report::{Level, Report, ReportBuilder, CodeLoc, Label};
+use crate::compiler::report::{Level, Report, ReportBuilder, CodeLoc, Label, Footer};
 
 /// Error returned while serializing/deserializing compiled rules.
 #[derive(Error, Debug)]
@@ -203,7 +203,7 @@ pub struct MismatchingTypes {
 #[associated_enum(CompileError)]
 #[error(code = "E004", title = "wrong arguments")]
 #[label("wrong arguments in this call", error_loc)]
-#[note(note)]
+#[footer(note)]
 pub struct WrongArguments {
     report: Report,
     error_loc: CodeLoc,
@@ -263,7 +263,7 @@ pub struct UnknownField {
 #[associated_enum(CompileError)]
 #[error(code = "E009", title = "unknown identifier `{identifier}`")]
 #[label("this identifier has not been declared", identifier_loc)]
-#[note(note)]
+#[footer(note)]
 pub struct UnknownIdentifier {
     report: Report,
     identifier: String,
@@ -346,7 +346,7 @@ pub struct ConflictingRuleIdentifier {
 #[associated_enum(CompileError)]
 #[error(code = "E014", title = "invalid regular expression")]
 #[label("{error}", error_loc)]
-#[note(note)]
+#[footer(note)]
 pub struct InvalidRegexp {
     report: Report,
     error: String,
@@ -376,7 +376,7 @@ pub struct MixedGreediness {
 #[associated_enum(CompileError)]
 #[error(code = "E016", title = "no matching patterns")]
 #[label("there's no pattern in this set", error_loc)]
-#[note(note)]
+#[footer(note)]
 pub struct EmptyPatternSet {
     report: Report,
     error_loc: CodeLoc,
@@ -417,7 +417,7 @@ pub struct SlowPattern {
 )]
 #[label("`{modifier1}` modifier used here", modifier1_loc)]
 #[label("`{modifier2}` modifier used here", modifier2_loc)]
-#[note(note)]
+#[footer(note)]
 pub struct InvalidModifierCombination {
     report: Report,
     modifier1: String,
@@ -481,7 +481,7 @@ pub struct DuplicatePattern {
 #[associated_enum(CompileError)]
 #[error(code = "E024", title = "invalid pattern `{pattern_ident}`")]
 #[label("{error}", error_loc)]
-#[note(note)]
+#[footer(note)]
 pub struct InvalidPattern {
     report: Report,
     pattern_ident: String,

lib/src/compiler/mod.rs

@@ -725,7 +725,6 @@ impl<'a> Compiler<'a> {
         };
 
         rules.build_ac_automaton();
-
         rules
     }
 

lib/src/compiler/report.rs

@@ -92,7 +92,7 @@ pub(crate) struct Report {
     code: &'static str,
     title: String,
     labels: Vec<(Level, CodeLoc, String)>,
-    note: Option<String>,
+    footers: Vec<(Level, String)>,
 }
 
 impl Report {
@@ -112,22 +112,21 @@ impl Report {
             let code_origin =
                 code_cache.get(&source_id).unwrap().origin.clone();
 
-            let level = match level {
-                Level::Error => "error",
-                Level::Warning => "warning",
-                Level::Info => "info",
-                Level::Note => "note",
-                Level::Help => "help",
-            };
-
-            Label { level, code_origin, span: code_loc.span.clone(), text }
+            Label {
+                level: level_as_text(*level),
+                code_origin,
+                span: code_loc.span.clone(),
+                text,
+            }
         })
     }
 
-    /// Returns the report's note.
+    /// Returns the report's footers.
     #[inline]
-    pub(crate) fn note(&self) -> Option<&str> {
-        self.note.as_deref()
+    pub(crate) fn footers(&self) -> impl Iterator<Item = Footer> {
+        self.footers
+            .iter()
+            .map(|(level, text)| Footer { level: level_as_text(*level), text })
     }
 }
 
@@ -140,7 +139,7 @@ impl Serialize for Report {
         s.serialize_field("code", &self.code)?;
         s.serialize_field("title", &self.title)?;
         s.serialize_field("labels", &self.labels().collect::<Vec<_>>())?;
-        s.serialize_field("note", &self.note)?;
+        s.serialize_field("footers", &self.footers().collect::<Vec<_>>())?;
         s.serialize_field("text", &self.to_string())?;
         s.end()
     }
@@ -152,7 +151,7 @@ impl PartialEq for Report {
             && self.code.eq(other.code)
             && self.title.eq(&other.title)
             && self.labels.eq(&other.labels)
-            && self.note.eq(&other.note)
+            && self.footers.eq(&other.footers)
     }
 }
 
@@ -210,8 +209,8 @@ impl Display for Report {
 
         message = message.snippet(snippet);
 
-        if let Some(note) = &self.note {
-            message = message.footer(Level::Note.title(note.as_str()));
+        for (level, text) in &self.footers {
+            message = message.footer(level.title(text.as_str()));
         }
 
         let renderer = if self.with_colors {
@@ -236,6 +235,13 @@ pub struct Label<'a> {
     text: &'a str,
 }
 
+/// Represents a footer in an error or warning report.
+#[derive(Serialize)]
+pub struct Footer<'a> {
+    level: &'a str,
+    text: &'a str,
+}
+
 /// Builds error and warning reports.
 ///
 /// `ReportBuilder` helps to create error and warning reports. It stores a copy
@@ -373,11 +379,19 @@ impl ReportBuilder {
         code: &'static str,
         title: String,
         labels: Vec<(Level, CodeLoc, String)>,
-        note: Option<String>,
+        footers: Vec<(Level, Option<String>)>,
     ) -> Report {
         // Make sure there's at least one label.
         assert!(!labels.is_empty());
 
+        // Remove footers where text is None.
+        let footers = footers
+            .into_iter()
+            .filter_map(|(level, text)| {
+                text.map(|text| (level, text))
+            })
+            .collect();
+
         Report {
             code_cache: self.code_cache.clone(),
             with_colors: self.with_colors,
@@ -389,7 +403,17 @@ impl ReportBuilder {
             code,
             title,
             labels,
-            note,
+            footers,
         }
     }
 }
+
+fn level_as_text(level: Level) -> &'static str {
+    match level {
+        Level::Error => "error",
+        Level::Warning => "warning",
+        Level::Info => "info",
+        Level::Note => "note",
+        Level::Help => "help",
+    }
+}

lib/src/compiler/tests/mod.rs

@@ -756,7 +756,7 @@ fn errors_serialization() {
                 "text": "this identifier has not been declared"
             }
         ],
-        "note": null,
+        "footers": [],
         "text": r#"error[E009]: unknown identifier `foo`
  --> test.yar:1:23
   |

lib/src/compiler/warnings.rs

@@ -8,7 +8,7 @@ use thiserror::Error;
 use yara_x_macros::ErrorEnum;
 use yara_x_macros::ErrorStruct;
 
-use crate::compiler::report::{Level, Report, ReportBuilder, CodeLoc, Label};
+use crate::compiler::report::{Level, Report, ReportBuilder, CodeLoc, Label, Footer};
 
 /// A warning raised while compiling YARA rules.
 #[allow(missing_docs)]
@@ -169,7 +169,7 @@ pub struct PotentiallyUnsatisfiableExpression {
     "this expression is always {expr_value}",
     expr_loc
 )]
-#[note(note)]
+#[footer(note)]
 pub struct InvariantBooleanExpression {
     report: Report,
     expr_value: bool,
@@ -200,7 +200,7 @@ pub struct InvariantBooleanExpression {
     "this expression is `{expr_type}` but is being used as `bool`",
     expr_loc
 )]
-#[note(note)]
+#[footer(note)]
 pub struct NonBooleanAsBoolean {
     report: Report,
     expr_type: String,
@@ -383,7 +383,7 @@ pub struct SlowPattern {
     "module `{module_name}` used here",
     module_name_loc
 )]
-#[note(note)]
+#[footer(note)]
 pub struct IgnoredModule {
     report: Report,
     module_name: String,