Add fallback location for results without file locations (#819)

Author: cosmir17

deny.toml

@@ -13,6 +13,9 @@ all-features = true
 [advisories]
 unmaintained = "workspace"
 ignore = [
+    # gix-date 0.11.0 vulnerability via tame-index 0.25.0 -> gix 0.75.0
+    # Waiting for tame-index to update to gix 0.77+
+    { id = "RUSTSEC-2025-0140", reason = "tame-index 0.25.0 pins gix 0.75.0; no updated version available yet" },
 ]
 
 [bans]

src/cargo-deny/check.rs

@@ -548,7 +548,8 @@ fn print_diagnostics(
     use cargo_deny::diag::Check;
 
     if log_ctx.format == crate::Format::Sarif {
-        let mut sc = cargo_deny::sarif::SarifCollector::default();
+        let workspace_root = krates.map_or("", |k| k.workspace_root().as_str());
+        let mut sc = cargo_deny::sarif::SarifCollector::new(workspace_root);
 
         for pack in rx {
             sc.add_diagnostics(pack, files);

src/sarif/collector.rs

@@ -1,7 +1,7 @@
 use crate::diag::Extra;
 use crate::sarif::model::{
-    DefaultConfiguration, Driver, Help, Location, Message, Result as SarifResult, Rule,
-    RuleProperties, Run, SarifLog, TextContent, Tool,
+    ArtifactLocation, DefaultConfiguration, Driver, Help, Location, Message, PhysicalLocation,
+    Region, Result as SarifResult, Rule, RuleProperties, Run, SarifLog, TextContent, Tool,
 };
 use crate::{
     Kid,
@@ -14,6 +14,7 @@ use std::fmt::Write as _;
 pub struct SarifCollector {
     diagnostics: Vec<DiagnosticData>,
     rules: BTreeMap<DiagnosticCode, RuleData>,
+    workspace_root: String,
 }
 
 struct DiagnosticData {
@@ -31,17 +32,15 @@ struct RuleData {
     description: &'static str,
 }
 
-#[allow(clippy::derivable_impls)]
-impl Default for SarifCollector {
-    fn default() -> Self {
+impl SarifCollector {
+    pub fn new(workspace_root: impl Into<String>) -> Self {
         Self {
             diagnostics: Vec::new(),
             rules: BTreeMap::new(),
+            workspace_root: workspace_root.into(),
         }
     }
-}
 
-impl SarifCollector {
     pub fn add_diagnostics(&mut self, pack: Pack, files: &crate::diag::Files) {
         for diag in pack {
             let Some(code) = diag.code else {
@@ -255,11 +254,37 @@ impl SarifCollector {
                     }
                 }
 
+                // GitHub Code Scanning requires at least one location per result.
+                // If no locations were found (e.g., for dependency advisories that only
+                // reference Cargo.lock which is filtered out), add a fallback location
+                // pointing to the workspace Cargo.toml since that's where dependencies are declared.
+                let locations = if diag.locations.is_empty() {
+                    let fallback_uri = if self.workspace_root.is_empty() {
+                        "Cargo.toml".to_string()
+                    } else {
+                        format!("{}/Cargo.toml", self.workspace_root)
+                    };
+                    vec![Location {
+                        physical_location: PhysicalLocation {
+                            artifact_location: ArtifactLocation { uri: fallback_uri },
+                            region: Region {
+                                start_line: 1,
+                                byte_offset: 0,
+                                byte_length: 0,
+                                snippet: None,
+                                message: None,
+                            },
+                        },
+                    }]
+                } else {
+                    diag.locations
+                };
+
                 SarifResult {
                     rule_id,
                     message: diag.message,
                     level: severity_to_sarif_level(diag.severity),
-                    locations: diag.locations,
+                    locations,
                     partial_fingerprints: fingerprints,
                 }
             })

tests/sarif.rs

@@ -21,7 +21,8 @@ where
             runner(cctx, tx);
         },
         || {
-            let mut sarif = cargo_deny::sarif::SarifCollector::default();
+            let workspace_root = ctx.krates.workspace_root().as_str();
+            let mut sarif = cargo_deny::sarif::SarifCollector::new(workspace_root);
 
             let default = if std::env::var_os("CI").is_some() {
                 60
@@ -64,11 +65,20 @@ where
     // so rather than try and fail, just redact manually
     for res in &mut sl.runs[0].results {
         for loc in &mut res.locations {
-            loc.physical_location.artifact_location.uri = loc
-                .physical_location
-                .artifact_location
-                .uri
-                .replace(root.as_str(), "{CWD}");
+            let uri = &mut loc.physical_location.artifact_location.uri;
+            // First try standard CWD replacement
+            *uri = uri.replace(root.as_str(), "{CWD}");
+
+            // Handle stale absolute paths from pre-computed test metadata (e.g., sarif_advisories)
+            // by normalizing any remaining absolute path containing known project subdirectories
+            if uri.starts_with('/') {
+                for marker in ["/cargo-deny/examples/", "/cargo-deny/tests/"] {
+                    if let Some(pos) = uri.find(marker) {
+                        *uri = format!("{{CWD}}{}", &uri[pos + "/cargo-deny".len()..]);
+                        break;
+                    }
+                }
+            }
         }
 
         for fp in res.partial_fingerprints.values_mut() {