Merge pull request golang#374 from EwanValentine/feature/create-toml-…

…file-examples-on-init

ADDED example comment to toml file on init golang#343

cmd/dep/testdata/harness_tests/ensure/empty/case1/final/Gopkg.toml

@@ -0,0 +1,9 @@
+
+# Example:
+# [[dependencies]]
+# source = "https://github.com/myfork/package.git"
+# branch = "master"
+# name = "github.com/vendor/package"
+# Note: revision will depend on your repository type, i.e git, svc, bzr etc...
+# revision = "abc123"
+# version = "1.0.0"

cmd/dep/testdata/harness_tests/init/skip-hidden/final/Gopkg.toml

@@ -0,0 +1,9 @@
+
+# Example:
+# [[dependencies]]
+# source = "https://github.com/myfork/package.git"
+# branch = "master"
+# name = "github.com/vendor/package"
+# Note: revision will depend on your repository type, i.e git, svc, bzr etc...
+# revision = "abc123"
+# version = "1.0.0"

fs.go

@@ -65,6 +65,14 @@ func writeFile(path string, in toml.Marshaler) error {
 	return err
 }
 
+// modifyWithString modifies a given file with a new string input.
+// This is used to write arbitrary string data to a file, such as
+// updating the `Gopkg.toml` file with example data if no deps found
+// on init.
+func modifyWithString(path, data string) error {
+	return ioutil.WriteFile(path, []byte(data), 0644)
+}
+
 // renameWithFallback attempts to rename a file or directory, but falls back to
 // copying in the event of a cross-link device error. If the fallback copy
 // succeeds, src is still removed, emulating normal rename behavior.

manifest.go

@@ -140,6 +140,14 @@ func (m *Manifest) toRaw() rawManifest {
 	return raw
 }
 
+// IsEmpty - Checks if payload is empty
+func (m *Manifest) IsEmpty() bool {
+	if len(m.Ovr) == 0 && len(m.Ignored) == 0 && len(m.Dependencies) == 0 && len(m.Required) == 0 {
+		return true
+	}
+	return false
+}
+
 type sortedRawProjects []rawProject
 
 func (s sortedRawProjects) Len() int      { return len(s) }

txn_writer.go

@@ -18,6 +18,20 @@ import (
 	"github.com/sdboyer/gps"
 )
 
+// Example string to be written to the manifest file
+// if no dependencies are found in the project
+// during `dep init`
+const exampleToml = `
+# Example:
+# [[dependencies]]
+# source = "https://github.com/myfork/package.git"
+# branch = "master"
+# name = "github.com/vendor/package"
+# Note: revision will depend on your repository type, i.e git, svc, bzr etc...
+# revision = "abc123"
+# version = "1.0.0"
+`
+
 // SafeWriter transactionalizes writes of manifest, lock, and vendor dir, both
 // individually and in any combination, into a pseudo-atomic action with
 // transactional rollback.
@@ -175,6 +189,7 @@ const (
 // - If oldLock is provided without newLock, error.
 // - If vendor is VendorAlways without a newLock, error.
 func (sw *SafeWriter) Prepare(manifest *Manifest, oldLock, newLock *Lock, vendor VendorBehavior) error {
+
 	sw.Payload = &SafeWriterPayload{
 		Manifest: manifest,
 		Lock:     newLock,
@@ -230,6 +245,7 @@ func (payload SafeWriterPayload) validate(root string, sm gps.SourceManager) err
 // This mostly guarantees that dep cannot exit with a partial write that would
 // leave an undefined state on disk.
 func (sw *SafeWriter) Write(root string, sm gps.SourceManager) error {
+
 	if sw.Payload == nil {
 		return errors.New("Cannot call SafeWriter.Write before SafeWriter.Prepare")
 	}
@@ -255,7 +271,12 @@ func (sw *SafeWriter) Write(root string, sm gps.SourceManager) error {
 	defer os.RemoveAll(td)
 
 	if sw.Payload.HasManifest() {
-		if err := writeFile(filepath.Join(td, ManifestName), sw.Payload.Manifest); err != nil {
+		if sw.Payload.Manifest.IsEmpty() {
+			err := modifyWithString(filepath.Join(td, ManifestName), exampleToml)
+			if err != nil {
+				return errors.Wrap(err, "failed to generate example text")
+			}
+		} else if err := writeFile(filepath.Join(td, ManifestName), sw.Payload.Manifest); err != nil {
 			return errors.Wrap(err, "failed to write manifest file to temp dir")
 		}
 	}