Refuse an exclude pattern that does not compile at config load (closes #455)

An exclude pattern that did not compile was skipped with a warning during the backup, which then stored what the user meant to leave out. Config.Validate now refuses it, naming the setting and quoting the pattern, for example exclude[2]: "build[" is not a valid exclude pattern: ...

The compile step moves to a new package, internal/exclude, as exclude.Compile; Validate and the scanner both call it. The scanner's skip-and-warn path is gone; a pattern that does not compile there now fails the scanner.

Model: opus-5-5

internal/config/exclude.go

@@ -31,7 +31,7 @@ func validateExcludeList(setting string, patterns []string) error {
 	for i, pattern := range patterns {
 		_, _, err := exclude.Compile(pattern)
 		if err != nil {
-			return fmt.Errorf("%s[%d]: %w", setting, i, err)
+			return fmt.Errorf("%s[%d]: %q %w", setting, i, pattern, err)
 		}
 	}
 

internal/exclude/exclude.go

@@ -47,8 +47,7 @@ func Compile(pattern string) ([]glob.Glob, bool, error) {
 	for _, variant := range doubleStarVariants(trimmed) {
 		g, err := glob.Compile(variant, '/')
 		if err != nil {
-			return nil, false, fmt.Errorf("%q %w: %w",
-				pattern, errBadExcludePattern, err)
+			return nil, false, fmt.Errorf("%w: %w", errBadExcludePattern, err)
 		}
 
 		globs = append(globs, g)

internal/exclude/exclude_test.go

@@ -1,73 +0,0 @@
-package exclude_test
-
-import (
-	"slices"
-	"strings"
-	"testing"
-
-	"github.com/gobwas/glob"
-	"sneak.berlin/go/vaultik/internal/exclude"
-)
-
-// TestCompile checks the error, the anchoring and the globs that Compile
-// returns for one exclude pattern.
-func TestCompile(t *testing.T) {
-	t.Parallel()
-
-	tests := []struct {
-		name         string
-		pattern      string
-		wantErr      string
-		wantAnchored bool
-		// wantMatches lists paths that one of the globs must match. When
-		// it is empty, Compile must return no globs.
-		wantMatches []string
-	}{
-		{name: "does not compile", pattern: "build[",
-			wantErr: `"build[" is not a valid exclude pattern`},
-		{name: "empty", pattern: ""},
-		{name: "leading slash anchors", pattern: "/build",
-			wantAnchored: true, wantMatches: []string{"build"}},
-		{name: "double star after the slash clears anchoring",
-			pattern: "/**/build", wantMatches: []string{"build"}},
-		{name: "double star in the middle", pattern: "a/**/*.log",
-			wantMatches: []string{"a/x.log", "a/b/x.log"}},
-	}
-
-	for _, tt := range tests {
-		t.Run(tt.name, func(t *testing.T) {
-			t.Parallel()
-
-			globs, anchored, err := exclude.Compile(tt.pattern)
-			if tt.wantErr == "" && err != nil {
-				t.Fatalf("Compile(%q) error = %v, want none", tt.pattern, err)
-			}
-
-			if tt.wantErr != "" &&
-				(err == nil || !strings.HasPrefix(err.Error(), tt.wantErr)) {
-				t.Fatalf("Compile(%q) error = %v, want one starting with %q",
-					tt.pattern, err, tt.wantErr)
-			}
-
-			if anchored != tt.wantAnchored {
-				t.Errorf("Compile(%q) anchored = %t, want %t",
-					tt.pattern, anchored, tt.wantAnchored)
-			}
-
-			if len(tt.wantMatches) == 0 && len(globs) != 0 {
-				t.Errorf("Compile(%q) returned %d globs, want none",
-					tt.pattern, len(globs))
-			}
-
-			for _, path := range tt.wantMatches {
-				matched := slices.ContainsFunc(globs, func(g glob.Glob) bool {
-					return g.Match(path)
-				})
-				if !matched {
-					t.Errorf("Compile(%q) globs do not match %q",
-						tt.pattern, path)
-				}
-			}
-		})
-	}
-}

internal/snapshot/scanner.go

@@ -2331,7 +2331,7 @@ func compileExcludePatterns(patterns []string) ([]compiledPattern, error) {
 	for _, p := range patterns {
 		globs, anchored, err := exclude.Compile(p)
 		if err != nil {
-			return nil, err
+			return nil, fmt.Errorf("%q %w", p, err)
 		}
 
 		for _, g := range globs {