Add diag.SafeDiagnostics class (#2927)

## Changes
A new helper to update diags from multiple threads. Also includes
shortcuts for frequently used Error and Errorf.

## Why
Simpler and less error-prone code in mutators.
Using this in #2926

## Tests
Existing tests.

Author: denik

bundle/apps/upload_config.go

@@ -6,7 +6,6 @@ import (
 	"fmt"
 	"path"
 	"strings"
-	"sync"
 
 	"github.com/databricks/cli/bundle"
 	"github.com/databricks/cli/bundle/config/resources"
@@ -23,10 +22,9 @@ type uploadConfig struct {
 }
 
 func (u *uploadConfig) Apply(ctx context.Context, b *bundle.Bundle) diag.Diagnostics {
-	var diags diag.Diagnostics
+	var diags diag.SafeDiagnostics
 	errGroup, ctx := errgroup.WithContext(ctx)
 
-	mu := sync.Mutex{}
 	for key, app := range b.Config.Resources.Apps {
 		// If the app has a config, we need to deploy it first.
 		// It means we need to write app.yml file with the content of the config field
@@ -47,25 +45,23 @@ func (u *uploadConfig) Apply(ctx context.Context, b *bundle.Bundle) diag.Diagnos
 			errGroup.Go(func() error {
 				err := f.Write(ctx, path.Join(appPath, "app.yml"), buf, filer.OverwriteIfExists)
 				if err != nil {
-					mu.Lock()
-					diags = append(diags, diag.Diagnostic{
+					diags.Append(diag.Diagnostic{
 						Severity:  diag.Error,
 						Summary:   "Failed to save config",
 						Detail:    fmt.Sprintf("Failed to write %s file: %s", path.Join(app.SourceCodePath, "app.yml"), err),
 						Locations: b.Config.GetLocations("resources.apps." + key),
 					})
-					mu.Unlock()
 				}
 				return nil
 			})
 		}
 	}
 
 	if err := errGroup.Wait(); err != nil {
-		return diags.Extend(diag.FromErr(err))
+		diags.AppendError(err)
 	}
 
-	return diags
+	return diags.Diags
 }
 
 // Name implements bundle.Mutator.

bundle/config/validate/validate_sync_patterns.go

@@ -4,7 +4,6 @@ import (
 	"context"
 	"fmt"
 	"strings"
-	"sync"
 
 	"github.com/databricks/cli/bundle"
 	"github.com/databricks/cli/libs/diag"
@@ -43,9 +42,8 @@ func (v *validateSyncPatterns) Apply(ctx context.Context, b *bundle.Bundle) diag
 }
 
 func checkPatterns(patterns []string, path string, b *bundle.Bundle) (diag.Diagnostics, error) {
-	var mu sync.Mutex
 	var errs errgroup.Group
-	var diags diag.Diagnostics
+	var diags diag.SafeDiagnostics
 
 	for index, pattern := range patterns {
 		// If the pattern is negated, strip the negation prefix
@@ -67,18 +65,16 @@ func checkPatterns(patterns []string, path string, b *bundle.Bundle) (diag.Diagn
 
 			if len(all) == 0 {
 				path := fmt.Sprintf("%s[%d]", path, index)
-				mu.Lock()
-				diags = diags.Append(diag.Diagnostic{
+				diags.Append(diag.Diagnostic{
 					Severity:  diag.Warning,
 					Summary:   fmt.Sprintf("Pattern %s does not match any files", pattern),
 					Locations: b.Config.GetLocations(path),
 					Paths:     []dyn.Path{dyn.MustPathFromString(path)},
 				})
-				mu.Unlock()
 			}
 			return nil
 		})
 	}
 
-	return diags, errs.Wait()
+	return diags.Diags, errs.Wait()
 }

libs/diag/diagnostic.go

@@ -3,6 +3,7 @@ package diag
 import (
 	"errors"
 	"fmt"
+	"sync"
 
 	"github.com/databricks/cli/libs/dyn"
 )
@@ -146,3 +147,30 @@ func (ds Diagnostics) Filter(severity Severity) Diagnostics {
 	}
 	return out
 }
+
+type SafeDiagnostics struct {
+	Mutex sync.Mutex
+	Diags Diagnostics
+}
+
+func (t *SafeDiagnostics) Append(d Diagnostic) {
+	t.Mutex.Lock()
+	defer t.Mutex.Unlock()
+
+	t.Diags = t.Diags.Append(d)
+}
+
+func (t *SafeDiagnostics) Extend(other Diagnostics) {
+	t.Mutex.Lock()
+	defer t.Mutex.Unlock()
+
+	t.Diags = t.Diags.Extend(other)
+}
+
+func (t *SafeDiagnostics) AppendErrorf(msg string, args ...any) {
+	t.Extend(FromErr(fmt.Errorf(msg, args...)))
+}
+
+func (t *SafeDiagnostics) AppendError(err error) {
+	t.Extend(FromErr(err))
+}