fix(init): If init has errors, rollback changes

If init has errors, simply bailing with an error isn't good enough. It
can leave our repo and working directory in unusable states. Instead,
we create a cleanup function that will undo work done so far, calling
any cleanup function that already exists.

Convert fsi_integration_test to new, simpler TestRunner methods.

base/component/component.go

@@ -13,7 +13,7 @@ import (
 type Component interface {
 	Base() *BaseComponent
 	Compare(Component) (bool, error)
-	WriteTo(dirPath string) error
+	WriteTo(dirPath string) (string, error)
 	RemoveFrom(dirPath string) error
 	DropDerivedValues()
 	LoadAndFill(*dataset.Dataset) error

base/component/kinds.go

@@ -34,8 +34,8 @@ func (fc *FilesysComponent) IsEmpty() bool {
 }
 
 // WriteTo writes the component as a file to the directory
-func (fc *FilesysComponent) WriteTo(dirPath string) error {
-	return fmt.Errorf("cannot write filesys component")
+func (fc *FilesysComponent) WriteTo(dirPath string) (string, error) {
+	return "", fmt.Errorf("cannot write filesys component")
 }
 
 // RemoveFrom removes the component file from the directory
@@ -82,8 +82,8 @@ func (dc *DatasetComponent) Compare(compare Component) (bool, error) {
 }
 
 // WriteTo writes the component as a file to the directory
-func (dc *DatasetComponent) WriteTo(dirPath string) error {
-	return fmt.Errorf("cannot write dataset component")
+func (dc *DatasetComponent) WriteTo(dirPath string) (string, error) {
+	return "", fmt.Errorf("cannot write dataset component")
 }
 
 // RemoveFrom removes the component file from the directory
@@ -134,6 +134,8 @@ func structToMap(value interface{}) (map[string]interface{}, error) {
 type MetaComponent struct {
 	BaseComponent
 	Value *dataset.Meta
+	// Prevent the component from being written. Used for testing.
+	DisableSerialization bool
 }
 
 // Compare compares to another component
@@ -152,15 +154,18 @@ func (mc *MetaComponent) Compare(compare Component) (bool, error) {
 }
 
 // WriteTo writes the component as a file to the directory
-func (mc *MetaComponent) WriteTo(dirPath string) error {
+func (mc *MetaComponent) WriteTo(dirPath string) (string, error) {
+	if mc.DisableSerialization {
+		return "", fmt.Errorf("serialization is disabled")
+	}
 	if err := mc.LoadAndFill(nil); err != nil {
-		return err
+		return "", err
 	}
 	// Okay to output an empty meta, we do so for `qri init`.
 	if mc.Value != nil {
 		return writeComponentFile(mc.Value, dirPath, "meta.json")
 	}
-	return nil
+	return "", nil
 }
 
 // RemoveFrom removes the component file from the directory
@@ -234,14 +239,14 @@ func (sc *StructureComponent) Compare(compare Component) (bool, error) {
 }
 
 // WriteTo writes the component as a file to the directory
-func (sc *StructureComponent) WriteTo(dirPath string) error {
+func (sc *StructureComponent) WriteTo(dirPath string) (string, error) {
 	if err := sc.LoadAndFill(nil); err != nil {
-		return err
+		return "", err
 	}
 	if sc.Value != nil && !sc.Value.IsEmpty() {
 		return writeComponentFile(sc.Value, dirPath, "structure.json")
 	}
-	return nil
+	return "", nil
 }
 
 // RemoveFrom removes the component file from the directory
@@ -313,14 +318,14 @@ func (cc *CommitComponent) Compare(compare Component) (bool, error) {
 }
 
 // WriteTo writes the component as a file to the directory
-func (cc *CommitComponent) WriteTo(dirPath string) error {
+func (cc *CommitComponent) WriteTo(dirPath string) (string, error) {
 	if err := cc.LoadAndFill(nil); err != nil {
-		return err
+		return "", err
 	}
 	if cc.Value != nil && !cc.Value.IsEmpty() {
 		return writeComponentFile(cc.Value, dirPath, "commit.json")
 	}
-	return nil
+	return "", nil
 }
 
 // RemoveFrom removes the component file from the directory
@@ -489,23 +494,24 @@ func (bc *BodyComponent) StructuredData() (interface{}, error) {
 }
 
 // WriteTo writes the component as a file to the directory
-func (bc *BodyComponent) WriteTo(dirPath string) error {
+func (bc *BodyComponent) WriteTo(dirPath string) (string, error) {
 	if bc.Value == nil {
 		err := bc.LoadAndFill(nil)
 		if err != nil {
-			return err
+			return "", err
 		}
 	}
 	body := bc.Value
 	if bc.Structure == nil {
-		return fmt.Errorf("cannot write body without a structure")
+		return "", fmt.Errorf("cannot write body without a structure")
 	}
 	data, err := SerializeBody(body, bc.Structure)
 	if err != nil {
-		return err
+		return "", err
 	}
 	bodyFilename := fmt.Sprintf("body.%s", bc.Format)
-	return ioutil.WriteFile(filepath.Join(dirPath, bodyFilename), data, os.ModePerm)
+	targetFile := filepath.Join(dirPath, bodyFilename)
+	return targetFile, ioutil.WriteFile(targetFile, data, os.ModePerm)
 }
 
 // RemoveFrom removes the component file from the directory
@@ -579,17 +585,17 @@ func (rc *ReadmeComponent) Compare(compare Component) (bool, error) {
 }
 
 // WriteTo writes the component as a file to the directory
-func (rc *ReadmeComponent) WriteTo(dirPath string) error {
+func (rc *ReadmeComponent) WriteTo(dirPath string) (string, error) {
 	if err := rc.LoadAndFill(nil); err != nil {
-		return err
+		return "", err
 	}
 	if rc.Value != nil && !rc.Value.IsEmpty() {
-		filename := filepath.Join(dirPath, fmt.Sprintf("readme.%s", rc.Format))
-		if err := ioutil.WriteFile(filename, rc.Value.ScriptBytes, os.ModePerm); err != nil {
-			return err
+		targetFile := filepath.Join(dirPath, fmt.Sprintf("readme.%s", rc.Format))
+		if err := ioutil.WriteFile(targetFile, rc.Value.ScriptBytes, os.ModePerm); err != nil {
+			return targetFile, err
 		}
 	}
-	return nil
+	return "", nil
 }
 
 // RemoveFrom removes the component file from the directory
@@ -737,15 +743,16 @@ func compareComponentData(first interface{}, second interface{}) (bool, error) {
 	return string(left) == string(rite), nil
 }
 
-func writeComponentFile(value interface{}, dirPath string, basefile string) error {
+func writeComponentFile(value interface{}, dirPath string, basefile string) (string, error) {
 	data, err := json.MarshalIndent(value, "", " ")
 	if err != nil {
-		return err
+		return "", err
 	}
 	// TODO(dlong): How does this relate to Base.SourceFile? Should respect that.
-	err = ioutil.WriteFile(filepath.Join(dirPath, basefile), data, os.ModePerm)
+	targetFile := filepath.Join(dirPath, basefile)
+	err = ioutil.WriteFile(targetFile, data, os.ModePerm)
 	if err != nil {
-		return err
+		return "", err
 	}
-	return nil
+	return targetFile, nil
 }