From 7d7951a223f5502af98a4c9b86ce0c5af22adf41 Mon Sep 17 00:00:00 2001
From: Carlos Alexandro Becker <caarlos0@users.noreply.github.com>
Date: Thu, 17 Jan 2019 10:50:00 -0200
Subject: [PATCH] feat: template on flags (#923)

---
 internal/builders/golang/build.go      |  6 +++++-
 internal/builders/golang/build_test.go | 24 ++++++++++++++++++++++++
 www/content/build.md                   |  3 ++-
 3 files changed, 31 insertions(+), 2 deletions(-)

diff --git a/internal/builders/golang/build.go b/internal/builders/golang/build.go
index f1e490a92..b3651aaeb 100644
--- a/internal/builders/golang/build.go
+++ b/internal/builders/golang/build.go
@@ -60,7 +60,11 @@ func (*Builder) Build(ctx *context.Context, build config.Build, options api.Opti
 	}
 	cmd := []string{"go", "build"}
 
-	cmd = append(cmd, build.Flags...)
+	flags, err := processFlags(ctx, build.Flags, "")
+	if err != nil {
+		return err
+	}
+	cmd = append(cmd, flags...)
 
 	asmflags, err := processFlags(ctx, build.Asmflags, "-asmflags=")
 	if err != nil {
diff --git a/internal/builders/golang/build_test.go b/internal/builders/golang/build_test.go
index 77af0a369..5099efcfb 100644
--- a/internal/builders/golang/build_test.go
+++ b/internal/builders/golang/build_test.go
@@ -91,10 +91,12 @@ func TestBuild(t *testing.T) {
 				},
 				Asmflags: []string{".=", "all="},
 				Gcflags:  []string{"all="},
+				Flags:    []string{"{{.Env.GO_FLAGS}}"},
 			},
 		},
 	}
 	var ctx = context.New(config)
+	ctx.Env["GO_FLAGS"] = "-v"
 	ctx.Git.CurrentTag = "5.6.7"
 	var build = ctx.Config.Builds[0]
 	for _, target := range build.Targets {
@@ -277,6 +279,28 @@ func TestRunInvalidLdflags(t *testing.T) {
 	assert.EqualError(t, err, `template: tmpl:1: unexpected "}" in operand`)
 }
 
+func TestRunInvalidFlags(t *testing.T) {
+	folder, back := testlib.Mktmp(t)
+	defer back()
+	writeGoodMain(t, folder)
+	var config = config.Project{
+		Builds: []config.Build{
+			{
+				Binary: "nametest",
+				Flags:  []string{"{{.Env.GOOS}"},
+				Targets: []string{
+					runtimeTarget,
+				},
+			},
+		},
+	}
+	var ctx = context.New(config)
+	var err = Default.Build(ctx, ctx.Config.Builds[0], api.Options{
+		Target: runtimeTarget,
+	})
+	assert.EqualError(t, err, `template: tmpl:1: unexpected "}" in operand`)
+}
+
 func TestRunPipeWithoutMainFunc(t *testing.T) {
 	folder, back := testlib.Mktmp(t)
 	defer back()
diff --git a/www/content/build.md b/www/content/build.md
index 547b9f29e..f85a2ad3e 100644
--- a/www/content/build.md
+++ b/www/content/build.md
@@ -25,10 +25,11 @@ builds:
     # Default is the name of the project directory.
     binary: program
 
-    # Set flags for custom build tags.
+    # Custom flags templates.
     # Default is empty.
     flags:
       - -tags=dev
+      - -v
 
     # Custom asmflags templates.
     # Default is empty.