Wrong patch is generated with DiffTimeout = 0

[tkf]

I think the patch generated by the following code is wrong:

package main

import (
    "io"
    "os"

    "github.com/sergi/go-diff/diffmatchpatch"
)

const (
    text1 = "Lorem ipsum dolor sit amet, consectetur adipiscing elit. Vivamus ut risus et enim consectetur convallis a non ipsum. Sed nec nibh cursus, interdum libero vel."
    text2 = "Lorem a ipsum dolor sit amet, consectetur adipiscing elit. Vivamus ut risus et enim consectetur convallis a non ipsum. Sed nec nibh cursus, interdum liberovel."
)

func main() {
    dmp := diffmatchpatch.New()
    dmp.DiffTimeout = 0
    // dmp.DiffTimeout = time.Hour  // it works
    diffs := dmp.DiffMain(text1, text2, true)
    diffs = dmp.DiffCleanupSemantic(diffs)
    patches := dmp.PatchMake(text1, diffs)
    io.WriteString(os.Stdout, dmp.PatchToText(patches))
}

It generates:

@@ -1,17 +1,18 @@
 Lorem
+a
 ro
-
 um dolor

However, the correct patch would be:

@@ -1,14 +1,16 @@
 Lorem
+a
 ipsum do
@@ -148,13 +148,12 @@
 m libero
-
 vel.

which is generated by setting dmp.DiffTimeout = time.Hour. Note that C++ implementation (with timeout=0) also generates the latter patch.

[alecmev]

Setting checklines to false produces a correct patch. Don't know what the cause is, but from a quick glance at diffCompute, it seems that it makes no sense to have no deadline and checklines enabled at the same time, since they have contradictory effects (DiffTimeout = 0 tells the lib to take its time and produce the best diff possible, while checklines = true tells it to compromise quality for performance). This combo is completely missing in the tests.

[zimmski]

I tested your example with the latest master, it outputs

@@ -1,14 +1,16 @@
 Lorem 
+a 
 ipsum do
@@ -148,13 +148,12 @@
 m libero
- 
 vel.

[zimmski]

To be more verbose. I can confirm that with the old version you were probably using (i.e. bc2ef12) the problem was still present, but now with the current master it is not. Please give it a whirl :-)

I can also confirm that the provided example and its patch make sense. I will add is as a test case and I will adapt the current deadline code because it does not make any sense. At the moment, if 0 or a negative deadline is given, the code will use a deadline of a year. I mean, if we do not want a deadline, we are serious about that, right?