From 6e882c50fa85aba34e4204e1016bc36ab09a617f Mon Sep 17 00:00:00 2001
From: Alessandro Arzilli <alessandro.arzilli@gmail.com>
Date: Sat, 22 Oct 2016 07:04:03 +0200
Subject: [PATCH] debugger/locations: prioritize exact matches of function
 names (#651)

If the location specification matches the name of a function exactly
return that function as a match event if the expression matches other
functions as well.

Without this some functions, like math/rand.Intn are unmatchable.
---
 _fixtures/locationsprog3.go       | 12 ++++++++++++
 service/debugger/locations.go     |  8 ++++++--
 service/test/integration2_test.go | 12 ++++++++++++
 3 files changed, 30 insertions(+), 2 deletions(-)
 create mode 100644 _fixtures/locationsprog3.go

diff --git a/_fixtures/locationsprog3.go b/_fixtures/locationsprog3.go
new file mode 100644
index 00000000..430c9fde
--- /dev/null
+++ b/_fixtures/locationsprog3.go
@@ -0,0 +1,12 @@
+package main
+
+import (
+	"fmt"
+	"math/rand"
+	"runtime"
+)
+
+func main() {
+	runtime.Breakpoint()
+	fmt.Println(rand.Intn(10))
+}
diff --git a/service/debugger/locations.go b/service/debugger/locations.go
index c6eba685..0c85ae51 100644
--- a/service/debugger/locations.go
+++ b/service/debugger/locations.go
@@ -346,10 +346,14 @@ func (loc *NormalLocationSpec) Find(d *Debugger, scope *proc.EvalScope, locStr s
 				continue
 			}
 			if loc.FuncBase.Match(f.Sym) {
-				candidates = append(candidates, f.Name)
-				if len(candidates) >= maxFindLocationCandidates {
+				if loc.Base == f.Name {
+					// if an exact match for the function name is found use it
+					candidates = []string{f.Name}
 					break
 				}
+				if len(candidates) < maxFindLocationCandidates {
+					candidates = append(candidates, f.Name)
+				}
 			}
 		}
 	}
diff --git a/service/test/integration2_test.go b/service/test/integration2_test.go
index 52dd0f0f..2f2c68c6 100644
--- a/service/test/integration2_test.go
+++ b/service/test/integration2_test.go
@@ -666,6 +666,18 @@ func TestClientServer_FindLocationsAddr(t *testing.T) {
 	})
 }
 
+func TestClientServer_FindLocationsExactMatch(t *testing.T) {
+	// if an expression matches multiple functions but one of them is an exact
+	// match it should be used anyway.
+	// In this example "math/rand.Intn" would normally match "math/rand.Intn"
+	// and "math/rand.(*Rand).Intn" but since the first match is exact it
+	// should be prioritized.
+	withTestClient2("locationsprog3", t, func(c service.Client) {
+		<-c.Continue()
+		findLocationHelper(t, c, "math/rand.Intn", false, 1, 0)
+	})
+}
+
 func TestClientServer_EvalVariable(t *testing.T) {
 	withTestClient2("testvariables", t, func(c service.Client) {
 		state := <-c.Continue()