Function TestFuzzyReplace_EndingNormalization

agent/agentfiles/files_test.go:2084–2224

TestFuzzyReplace_EndingNormalization pins the line-ending rule. Rule: every spliced line gets the file's dominant ending, except when the caller signaled intent by making search and replace disagree on internal endings (both non-empty, different). Intent requires pass 1 to byte-match the file's end

(t *testing.T)

// ending, so a match covering the file's last line does not
// materialize a newline the file never had.
func TestFuzzyReplace_EndingNormalization(t *testing.T) {
	t.Parallel()

	tmpdir := os.TempDir()
	logger := slogtest.Make(t, &slogtest.Options{IgnoreErrors: true}).Leveled(slog.LevelDebug)

	type edit struct {
		search, replace string
		replaceAll      bool
	}
	tests := []struct {
		name     string
		content  string
		edits    []edit
		expected string
	}{
		// CRLF file, LF search, LF replace with expansion.
		// Internal endings agree (both LF), rule fires, every
		// spliced line becomes CRLF.
		{
			name:     "CRLFFile_LFSearchReplace_Expansion",
			content:  "line1\r\nline2\r\nline3\r\n",
			edits:    []edit{{search: "line1\nline2\n", replace: "line1\nINSERTED\nline2\n"}},
			expected: "line1\r\nINSERTED\r\nline2\r\nline3\r\n",
		},
		// CRLF file with no trailing newline, LF search/replace
		// with expansion that covers the file's last line. Interior
		// spliced lines become CRLF; final spliced line preserves
		// the file's no-EOL property.
		{
			name:     "CRLFFileNoEOL_LFSearchReplace_ExpansionAtEOF",
			content:  "alpha\r\nbeta\r\ngamma",
			edits:    []edit{{search: "gamma", replace: "gamma\ndelta\nepsilon"}},
			expected: "alpha\r\nbeta\r\ngamma\r\ndelta\r\nepsilon",
		},
		// CRLF Go file with no final newline; LLM sends LF
		// search/replace that expands the function body. This is
		// the motivating real-world case for the rule.
		{
			name:     "CRLFFileNoEOL_LFCallerExpandsFunctionBody",
			content:  "package main\r\n\r\nfunc main() {\r\n\tprintln(\"hi\")\r\n}",
			edits:    []edit{{search: "\tprintln(\"hi\")\n}", replace: "\tprintln(\"hi\")\n\tprintln(\"bye\")\n\treturn\n}"}},
			expected: "package main\r\n\r\nfunc main() {\r\n\tprintln(\"hi\")\r\n\tprintln(\"bye\")\r\n\treturn\r\n}",
		},
		// LF file, CRLF search/replace (caller sent CRLF, file is
		// LF). Internal endings agree (both CRLF). Rule fires, the
		// file's LF wins.
		{
			name:     "LFFile_CRLFSearchReplace_FileLFWins",
			content:  "one\ntwo\nthree\n",
			edits:    []edit{{search: "one\r\ntwo\r\n", replace: "ONE\r\nTWO\r\n"}},
			expected: "ONE\nTWO\nthree\n",
		},
		// Caller got endings right: CRLF in search, replace, and file.
		// Pins that normalization doesn't regress this happy path.
		{
			name:     "CRLFFile_CRLFSearchReplace_SanityPreserved",
			content:  "a\r\nb\r\nc\r\n",