iwp

src/ledger/file.go

@@ -49,7 +49,7 @@ func (files Files) TempSetLastNLines(n int, lines []string) error {
 	}
 	defer r.Close()
 
-	if _, err := peekLastNLines(w, r, n); err != nil {
+	if _, err := peekLastNLines(w, bufio.NewReader(r), n); err != nil {
 		return err
 	}
 	for i := range lines {

src/ledger/file_test.go

@@ -354,6 +354,47 @@ func TestFilesTempSetLastNLines(t *testing.T) {
 		want  string
 	}{
 		"empty": {},
+		"append to empty": {
+			input: []string{"hello", "world"},
+			n:     100,
+			want:  "hello\nworld\n",
+		},
+		"replace last 10 of 1 lines with 2": {
+			given: "ohno",
+			input: []string{"hello", "world"},
+			n:     10,
+			want:  "hello\nworld\n",
+		},
+		"replace last 1 of 1 lines with 2": {
+			given: "ohno",
+			input: []string{"hello", "world"},
+			n:     1,
+			want:  "hello\nworld\n",
+		},
+		"replace last 0 of 1 lines with 2": {
+			given: "ohno",
+			input: []string{"hello", "world"},
+			n:     0,
+			want:  "ohno\nhello\nworld\n",
+		},
+		"replace last 1 of 1 lines with 0": {
+			given: "ohno",
+			input: []string{},
+			n:     1,
+			want:  "",
+		},
+		"replace last 1 of 2 lines with 1": {
+			given: "ohno\nhaha",
+			input: []string{"replaced"},
+			n:     1,
+			want:  "ohno\nreplaced\n",
+		},
+		"replace last 1 of 2 lines with 2": {
+			given: "ohno\nhaha",
+			input: []string{"replac", "ed"},
+			n:     1,
+			want:  "ohno\nreplac\ned\n",
+		},
 	}
 
 	for name, d := range cases {
@@ -363,11 +404,18 @@ func TestFilesTempSetLastNLines(t *testing.T) {
 			os.WriteFile(p, []byte(c.given), os.ModePerm)
 			files := Files([]string{p})
 			if err := files.TempSetLastNLines(c.n, c.input); err != nil {
+				s := err.Error()
+				if _, err := os.Stat(s); err == nil {
+					got, _ := os.ReadFile(s)
+					if string(got) != c.want {
+						t.Errorf("want\n%s, got\n%s", c.want, got)
+					}
+				}
 				t.Fatal(err)
 			}
 			got, _ := os.ReadFile(p)
 			if string(got) != c.want {
-				t.Errorf("want\n\t%s, got\n\t%s", c.want, got)
+				t.Errorf("want\n%s, got\n%s", c.want, got)
 			}
 		})
 	}