From eb893525041a53b968a46000ed5cb66ffc725853 Mon Sep 17 00:00:00 2001 From: Phillip Wood Date: Thu, 9 Dec 2021 10:30:00 +0000 Subject: [PATCH] diff --color-moved: avoid false short line matches and bad zebra coloring When marking moved lines it is possible for a block of potential matched lines to extend past a change in sign when there is a sequence of added lines whose text matches the text of a sequence of deleted and added lines. Most of the time either `match` will be NULL or `pmb_advance_or_null()` will fail when the loop encounters a change of sign but there are corner cases where `match` is non-NULL and `pmb_advance_or_null()` successfully advances the moved block despite the change in sign. One consequence of this is highlighting a short line as moved when it should not be. For example -moved line # Correctly highlighted as moved +short line # Wrongly highlighted as moved context +moved line # Correctly highlighted as moved +short line context -short line The other consequence is coloring a moved addition following a moved deletion in the wrong color. In the example below the first "+moved line 3" should be highlighted as newMoved not newMovedAlternate. -moved line 1 # Correctly highlighted as oldMoved -moved line 2 # Correctly highlighted as oldMovedAlternate +moved line 3 # Wrongly highlighted as newMovedAlternate context # Everything else is highlighted correctly +moved line 2 +moved line 3 context +moved line 1 -moved line 3 These false matches are more likely when using --color-moved-ws with the exception of --color-moved-ws=allow-indentation-change which ties the sign of the current whitespace delta to the sign of the line to avoid this problem. The fix is to check that the sign of the new line being matched is the same as the sign of the line that started the block of potential matches. Signed-off-by: Phillip Wood Signed-off-by: Junio C Hamano --- diff.c | 17 ++++++---- t/t4015-diff-whitespace.sh | 65 ++++++++++++++++++++++++++++++++++++++ 2 files changed, 76 insertions(+), 6 deletions(-) diff --git a/diff.c b/diff.c index 53f0df7532..efba278935 100644 --- a/diff.c +++ b/diff.c @@ -1176,7 +1176,7 @@ static void mark_color_as_moved(struct diff_options *o, struct moved_block *pmb = NULL; /* potentially moved blocks */ int pmb_nr = 0, pmb_alloc = 0; int n, flipped_block = 0, block_length = 0; - enum diff_symbol last_symbol = 0; + enum diff_symbol moved_symbol = DIFF_SYMBOL_BINARY_DIFF_HEADER; for (n = 0; n < o->emitted_symbols->nr; n++) { @@ -1202,7 +1202,7 @@ static void mark_color_as_moved(struct diff_options *o, flipped_block = 0; } - if (!match) { + if (pmb_nr && (!match || l->s != moved_symbol)) { int i; if (!adjust_last_block(o, n, block_length) && @@ -1219,12 +1219,13 @@ static void mark_color_as_moved(struct diff_options *o, pmb_nr = 0; block_length = 0; flipped_block = 0; - last_symbol = l->s; + } + if (!match) { + moved_symbol = DIFF_SYMBOL_BINARY_DIFF_HEADER; continue; } if (o->color_moved == COLOR_MOVED_PLAIN) { - last_symbol = l->s; l->flags |= DIFF_SYMBOL_MOVED_LINE; continue; } @@ -1251,11 +1252,16 @@ static void mark_color_as_moved(struct diff_options *o, &pmb, &pmb_alloc, &pmb_nr); - if (contiguous && pmb_nr && last_symbol == l->s) + if (contiguous && pmb_nr && moved_symbol == l->s) flipped_block = (flipped_block + 1) % 2; else flipped_block = 0; + if (pmb_nr) + moved_symbol = l->s; + else + moved_symbol = DIFF_SYMBOL_BINARY_DIFF_HEADER; + block_length = 0; } @@ -1265,7 +1271,6 @@ static void mark_color_as_moved(struct diff_options *o, if (flipped_block && o->color_moved != COLOR_MOVED_BLOCKS) l->flags |= DIFF_SYMBOL_MOVED_LINE_ALT; } - last_symbol = l->s; } adjust_last_block(o, n, block_length); diff --git a/t/t4015-diff-whitespace.sh b/t/t4015-diff-whitespace.sh index 4e0fd76c6c..15782c879d 100755 --- a/t/t4015-diff-whitespace.sh +++ b/t/t4015-diff-whitespace.sh @@ -1514,6 +1514,71 @@ test_expect_success 'zebra alternate color is only used when necessary' ' test_cmp expected actual ' +test_expect_success 'short lines of opposite sign do not get marked as moved' ' + cat >old.txt <<-\EOF && + this line should be marked as moved + unchanged + unchanged + unchanged + unchanged + too short + this line should be marked as oldMoved newMoved + this line should be marked as oldMovedAlternate newMoved + unchanged 1 + unchanged 2 + unchanged 3 + unchanged 4 + this line should be marked as oldMoved newMoved/newMovedAlternate + EOF + cat >new.txt <<-\EOF && + too short + unchanged + unchanged + this line should be marked as moved + too short + unchanged + unchanged + this line should be marked as oldMoved newMoved/newMovedAlternate + unchanged 1 + unchanged 2 + this line should be marked as oldMovedAlternate newMoved + this line should be marked as oldMoved newMoved/newMovedAlternate + unchanged 3 + this line should be marked as oldMoved newMoved + unchanged 4 + EOF + test_expect_code 1 git diff --no-index --color --color-moved=zebra \ + old.txt new.txt >output && cat output && + grep -v index output | test_decode_color >actual && + cat >expect <<-\EOF && + diff --git a/old.txt b/new.txt + --- a/old.txt + +++ b/new.txt + @@ -1,13 +1,15 @@ + -this line should be marked as moved + +too short + unchanged + unchanged + +this line should be marked as moved + +too short + unchanged + unchanged + -too short + -this line should be marked as oldMoved newMoved + -this line should be marked as oldMovedAlternate newMoved + +this line should be marked as oldMoved newMoved/newMovedAlternate + unchanged 1 + unchanged 2 + +this line should be marked as oldMovedAlternate newMoved + +this line should be marked as oldMoved newMoved/newMovedAlternate + unchanged 3 + +this line should be marked as oldMoved newMoved + unchanged 4 + -this line should be marked as oldMoved newMoved/newMovedAlternate + EOF + test_cmp expect actual +' + test_expect_success 'cmd option assumes configured colored-moved' ' test_config color.diff.oldMoved "magenta" && test_config color.diff.newMoved "cyan" &&