Structural search: fix precise lang filtering (#63791)

The feature `search-content-based-lang-detection` was never implemented
for structural search. This PR fills in the missing pieces.

Fixes #61714
Relates to
https://linear.app/sourcegraph/project/make-precise-lang-filtering-default-4f06cfa28567

## Test plan

Two new unit tests checking that the lang filters are now correctly
passed to Zoekt.

cmd/searcher/internal/search/zoekt_search.go

@@ -22,7 +22,7 @@ import (
 	"github.com/sourcegraph/sourcegraph/lib/errors"
 )
 
-func handleFilePathPatterns(patternInfo *protocol.PatternInfo) (query.Q, error) {
+func handleSearchFilters(patternInfo *protocol.PatternInfo) (query.Q, error) {
 	var and []query.Q
 
 	// Zoekt uses regular expressions for file paths.
@@ -42,10 +42,18 @@ func handleFilePathPatterns(patternInfo *protocol.PatternInfo) (query.Q, error)
 		and = append(and, &query.Not{Child: q})
 	}
 
+	for _, lang := range patternInfo.IncludeLangs {
+		and = append(and, &query.Language{Language: lang})
+	}
+
+	for _, lang := range patternInfo.ExcludeLangs {
+		and = append(and, &query.Not{Child: &query.Language{Language: lang}})
+	}
+
 	return query.NewAnd(and...), nil
 }
 
-func buildQuery(pattern string, branchRepos []query.BranchRepos, filePathPatterns query.Q, shortcircuit bool) (query.Q, error) {
+func buildQuery(pattern string, branchRepos []query.BranchRepos, filterQuery query.Q, shortcircuit bool) (query.Q, error) {
 	regexString := comby.StructuralPatToRegexpQuery(pattern, shortcircuit)
 	if len(regexString) == 0 {
 		return &query.Const{Value: true}, nil
@@ -56,7 +64,7 @@ func buildQuery(pattern string, branchRepos []query.BranchRepos, filePathPattern
 	}
 	return query.NewAnd(
 		&query.BranchesRepos{List: branchRepos},
-		filePathPatterns,
+		filterQuery,
 		&query.Regexp{
 			Regexp:        re,
 			CaseSensitive: true,
@@ -87,13 +95,13 @@ func zoektSearch(ctx context.Context, logger log.Logger, client zoekt.Streamer,
 	}).ToSearchOptions(ctx)
 	searchOpts.Whole = true
 
-	filePathPatterns, err := handleFilePathPatterns(args)
+	filterQuery, err := handleSearchFilters(args)
 	if err != nil {
 		return err
 	}
 
 	t0 := time.Now()
-	q, err := buildQuery(atom.Value, branchRepos, filePathPatterns, false)
+	q, err := buildQuery(atom.Value, branchRepos, filterQuery, false)
 	if err != nil {
 		return err
 	}

cmd/searcher/internal/search/zoekt_search_test.go

@@ -62,3 +62,56 @@ func Test_zoektSearch(t *testing.T) {
 	)
 	require.Error(t, err)
 }
+
+func TestHandleSearchFilters(t *testing.T) {
+	tests := []struct {
+		name        string
+		patternInfo *protocol.PatternInfo
+		expectedQ   query.Q
+		expectedErr error
+	}{
+		{
+			name: "Include and exclude paths",
+			patternInfo: &protocol.PatternInfo{
+				IncludePaths:    []string{"\\.go", "cmd"},
+				ExcludePaths:    "vendor/",
+				IsCaseSensitive: false,
+			},
+			expectedQ: query.NewAnd(
+				&query.Substring{Pattern: ".go", FileName: true},
+				&query.Substring{Pattern: "cmd", FileName: true},
+				&query.Not{Child: &query.Substring{Pattern: "vendor/", FileName: true}},
+			),
+			expectedErr: nil,
+		},
+		{
+			name: "Include and exclude languages",
+			patternInfo: &protocol.PatternInfo{
+				IncludePaths: []string{"cmd"},
+				IncludeLangs: []string{"go", "typescript"},
+				ExcludeLangs: []string{"javascript"},
+			},
+			expectedQ: query.NewAnd(
+				&query.Substring{Pattern: "cmd", FileName: true},
+				&query.Language{Language: "go"},
+				&query.Language{Language: "typescript"},
+				&query.Not{Child: &query.Language{Language: "javascript"}},
+			),
+			expectedErr: nil,
+		},
+	}
+
+	for _, tt := range tests {
+		t.Run(tt.name, func(t *testing.T) {
+			q, err := handleSearchFilters(tt.patternInfo)
+
+			if tt.expectedErr != nil {
+				require.Error(t, err)
+				require.Equal(t, tt.expectedErr.Error(), err.Error())
+			} else {
+				require.NoError(t, err)
+				require.Equal(t, tt.expectedQ, q)
+			}
+		})
+	}
+}

internal/search/job/jobutil/job_test.go

@@ -1515,6 +1515,10 @@ func TestToTextPatternInfo(t *testing.T) {
 	}, {
 		input:  `repo:^github\.com/sgtest/sourcegraph-typescript$ file:^README\.md "basic :[_] access :[_]" patterntype:structural`,
 		output: autogold.Expect(`{"Query":{"Value":"\"basic :[_] access :[_]\"","IsNegated":false,"IsRegExp":false},"IsStructuralPat":true,"CombyRule":"","IsCaseSensitive":false,"FileMatchLimit":30,"Index":"yes","Select":[],"IncludePaths":["^README\\.md"],"ExcludePaths":"","IncludeLangs":null,"ExcludeLangs":null,"PathPatternsAreCaseSensitive":false,"PatternMatchesContent":true,"PatternMatchesPath":true,"Languages":null}`),
+	}, {
+		input:  `repo:^github\.com/sgtest/sourcegraph-typescript$ lang:typescript "basic :[_] access :[_]" patterntype:structural`,
+		feat:   search.Features{ContentBasedLangFilters: true},
+		output: autogold.Expect(`{"Query":{"Value":"\"basic :[_] access :[_]\"","IsNegated":false,"IsRegExp":false},"IsStructuralPat":true,"CombyRule":"","IsCaseSensitive":false,"FileMatchLimit":30,"Index":"yes","Select":[],"IncludePaths":null,"ExcludePaths":"","IncludeLangs":["TypeScript"],"ExcludeLangs":null,"PathPatternsAreCaseSensitive":false,"PatternMatchesContent":true,"PatternMatchesPath":true,"Languages":["typescript"]}`),
 	}, {
 		input:  `sgtest lang:magik type:file`,
 		feat:   search.Features{ContentBasedLangFilters: true},