Use better error assertions and clean up locker API (#490)

## Changes
Some cleanup work

## Tests
Locker integration test passes

bundle/deployer/deployer.go

@@ -2,10 +2,12 @@ package deployer
 
 import (
 	"context"
+	"errors"
 	"fmt"
+	"io"
+	"io/fs"
 	"os"
 	"path/filepath"
-	"strings"
 
 	"github.com/databricks/cli/libs/locker"
 	"github.com/databricks/cli/libs/log"
@@ -97,22 +99,24 @@ func (b *Deployer) tfStateLocalPath() string {
 	return filepath.Join(b.DefaultTerraformRoot(), "terraform.tfstate")
 }
 
-func (b *Deployer) LoadTerraformState(ctx context.Context) error {
-	bytes, err := b.locker.GetRawJsonFileContent(ctx, b.tfStateRemotePath())
-	if err != nil {
+func (d *Deployer) LoadTerraformState(ctx context.Context) error {
+	r, err := d.locker.Read(ctx, d.tfStateRemotePath())
+	if errors.Is(err, fs.ErrNotExist) {
 		// If remote tf state is absent, use local tf state
-		if strings.Contains(err.Error(), "File not found.") {
-			return nil
-		} else {
-			return err
-		}
+		return nil
 	}
-	err = os.MkdirAll(b.DefaultTerraformRoot(), os.ModeDir)
 	if err != nil {
 		return err
 	}
-	err = os.WriteFile(b.tfStateLocalPath(), bytes, os.ModePerm)
-	return err
+	err = os.MkdirAll(d.DefaultTerraformRoot(), os.ModeDir)
+	if err != nil {
+		return err
+	}
+	b, err := io.ReadAll(r)
+	if err != nil {
+		return err
+	}
+	return os.WriteFile(d.tfStateLocalPath(), b, os.ModePerm)
 }
 
 func (b *Deployer) SaveTerraformState(ctx context.Context) error {
@@ -120,7 +124,7 @@ func (b *Deployer) SaveTerraformState(ctx context.Context) error {
 	if err != nil {
 		return err
 	}
-	return b.locker.PutFile(ctx, b.tfStateRemotePath(), bytes)
+	return b.locker.Write(ctx, b.tfStateRemotePath(), bytes)
 }
 
 func (d *Deployer) Lock(ctx context.Context, isForced bool) error {

internal/locker_test.go

@@ -4,6 +4,7 @@ import (
 	"context"
 	"encoding/json"
 	"fmt"
+	"io"
 	"io/fs"
 	"math/rand"
 	"sync"
@@ -114,18 +115,23 @@ func TestAccLock(t *testing.T) {
 		if i == indexOfActiveLocker {
 			continue
 		}
-		err := lockers[i].PutFile(ctx, "foo.json", []byte(`'{"surname":"Khan", "name":"Shah Rukh"}`))
+		err := lockers[i].Write(ctx, "foo.json", []byte(`'{"surname":"Khan", "name":"Shah Rukh"}`))
 		assert.ErrorContains(t, err, "failed to put file. deploy lock not held")
 	}
 
 	// active locker file write succeeds
-	err = lockers[indexOfActiveLocker].PutFile(ctx, "foo.json", []byte(`{"surname":"Khan", "name":"Shah Rukh"}`))
+	err = lockers[indexOfActiveLocker].Write(ctx, "foo.json", []byte(`{"surname":"Khan", "name":"Shah Rukh"}`))
 	assert.NoError(t, err)
 
-	// active locker file read succeeds with expected results
-	bytes, err := lockers[indexOfActiveLocker].GetRawJsonFileContent(ctx, "foo.json")
+	// read active locker file
+	r, err := lockers[indexOfActiveLocker].Read(ctx, "foo.json")
+	require.NoError(t, err)
+	b, err := io.ReadAll(r)
+	require.NoError(t, err)
+
+	// assert on active locker content
 	var res map[string]string
-	json.Unmarshal(bytes, &res)
+	json.Unmarshal(b, &res)
 	assert.NoError(t, err)
 	assert.Equal(t, "Khan", res["surname"])
 	assert.Equal(t, "Shah Rukh", res["name"])
@@ -135,7 +141,7 @@ func TestAccLock(t *testing.T) {
 		if i == indexOfActiveLocker {
 			continue
 		}
-		_, err = lockers[i].GetRawJsonFileContent(ctx, "foo.json")
+		_, err = lockers[i].Read(ctx, "foo.json")
 		assert.ErrorContains(t, err, "failed to get file. deploy lock not held")
 	}
 

libs/locker/locker.go

@@ -7,7 +7,7 @@ import (
 	"errors"
 	"fmt"
 	"io"
-	"strings"
+	"io/fs"
 	"time"
 
 	"github.com/databricks/cli/libs/filer"
@@ -88,7 +88,7 @@ func (locker *Locker) GetActiveLockState(ctx context.Context) (*LockState, error
 // holder details if locker does not hold the lock
 func (locker *Locker) assertLockHeld(ctx context.Context) error {
 	activeLockState, err := locker.GetActiveLockState(ctx)
-	if err != nil && strings.Contains(err.Error(), "File not found.") {
+	if errors.Is(err, fs.ErrNotExist) {
 		return fmt.Errorf("no active lock on target dir: %s", err)
 	}
 	if err != nil {
@@ -104,22 +104,18 @@ func (locker *Locker) assertLockHeld(ctx context.Context) error {
 }
 
 // idempotent function since overwrite is set to true
-func (locker *Locker) PutFile(ctx context.Context, pathToFile string, content []byte) error {
+func (locker *Locker) Write(ctx context.Context, pathToFile string, content []byte) error {
 	if !locker.Active {
 		return fmt.Errorf("failed to put file. deploy lock not held")
 	}
 	return locker.filer.Write(ctx, pathToFile, bytes.NewReader(content), filer.OverwriteIfExists, filer.CreateParentDirectories)
 }
 
-func (locker *Locker) GetRawJsonFileContent(ctx context.Context, path string) ([]byte, error) {
+func (locker *Locker) Read(ctx context.Context, path string) (io.ReadCloser, error) {
 	if !locker.Active {
 		return nil, fmt.Errorf("failed to get file. deploy lock not held")
 	}
-	reader, err := locker.filer.Read(ctx, path)
-	if err != nil {
-		return nil, err
-	}
-	return io.ReadAll(reader)
+	return locker.filer.Read(ctx, path)
 }
 
 func (locker *Locker) Lock(ctx context.Context, isForced bool) error {