chore: don't display filter used if empty (#8929)

crates/forge/bin/cmd/test/mod.rs

@@ -494,11 +494,21 @@ impl TestArgs {
             self.flamechart) &&
             num_filtered != 1
         {
+            let action = if self.flamegraph {
+                "generate a flamegraph"
+            } else if self.flamechart {
+                "generate a flamechart"
+            } else {
+                "run the debugger"
+            };
+            let filter = if filter.is_empty() {
+                String::new()
+            } else {
+                format!("\n\nFilter used:\n{filter}")
+            };
             eyre::bail!(
                 "{num_filtered} tests matched your criteria, but exactly 1 test must match in order to {action}.\n\n\
-                 Use --match-contract and --match-path to further limit the search.\n\
-                 Filter used:\n{filter}",
-                action = if self.flamegraph {"generate a flamegraph"} else if self.flamechart {"generate a flamechart"} else {"run the debugger"},
+                 Use --match-contract and --match-path to further limit the search.{filter}",
             );
         }
 

crates/forge/tests/cli/test_cmd.rs

@@ -2174,3 +2174,31 @@ Warning: the following cheatcode(s) are deprecated and will be removed in future
 "#]]);
     }
 );
+
+forgetest_init!(requires_single_test, |prj, cmd| {
+    cmd.args(["test", "--debug", "test"]).assert_failure().stderr_eq(str![[r#"
+Error: 
+2 tests matched your criteria, but exactly 1 test must match in order to run the debugger.
+
+Use --match-contract and --match-path to further limit the search.
+
+Filter used:
+	match-test: `test`
+
+
+"#]]);
+    cmd.forge_fuse().args(["test", "--flamegraph"]).assert_failure().stderr_eq(str![[r#"
+Error: 
+2 tests matched your criteria, but exactly 1 test must match in order to generate a flamegraph.
+
+Use --match-contract and --match-path to further limit the search.
+
+"#]]);
+    cmd.forge_fuse().args(["test", "--flamechart"]).assert_failure().stderr_eq(str![[r#"
+Error: 
+2 tests matched your criteria, but exactly 1 test must match in order to generate a flamechart.
+
+Use --match-contract and --match-path to further limit the search.
+
+"#]]);
+});