diff

func Apply ¶

func Apply(root types.Value, patch Patch) types.Value

Apply applies a Patch (list of diffs) to a graph. It fulfills the following contract:

Given 2 Noms graphs: a1 and a2:
  ApplyPatch(a1, Diff(a1, a2)) == a2

This is useful for IncrementalUpdate() and possibly other problems. See updater.go for more information.

This function uses a patchStack to maintain state of the graph as it cycles through the diffs in a patch, applying them to 'root' one by one. Because the Difference objects in the patch can be sorted according to their path, each one is applied in order. When done in combination with the stack, this enables all Differences that change a particular node to be applied to that node before it gets assigned back to it's parent.

func Diff ¶

func Diff(v1, v2 types.Value, dChan chan<- Difference, stopChan chan struct{}, leftRight bool)

Diff traverses two graphs simultaneously looking for differences. It returns two channels: a DiffReceiveChan that the caller can use to iterate over the diffs in the graph and a StopSendChanel that a caller can use to signal the Diff function to stop processing. Diff returns the Differences in depth-first first order. A 'diff' is defined as one of the following conditions:

• a Value is Added or Removed from a node in the graph
• the type of a Value has changed in the graph
• a primitive (i.e. Bool, Number, String, Ref or Blob) Value has changed

A Difference is not returned when a non-primitive value has been modified. For example, a struct field has been changed from one Value of type Employee to another. Those modifications are accounted for by the Differences described above at a lower point in the graph.

If leftRight is true then the left-right diff is used for ordered sequences - see Diff vs DiffLeftRight in Set and Map.

Note: the function sends messages on diffChan and checks whether stopChan has been closed to know if it needs to terminate diffing early. To function properly it needs to be executed concurrently with code that reads values from diffChan. The following is a typical invocation of Diff():

dChan := make(chan Difference)
sChan := make(chan struct{})
go func() {
    d.Diff(s3, s4, dChan, sChan, leftRight)
    close(dChan)
}()
for dif := range dChan {
    <some code>
}

func PrintDiff ¶

func PrintDiff(w io.Writer, v1, v2 types.Value, leftRight bool) (err error)

PrintDiff writes a textual reprensentation of the diff from |v1| to |v2| to |w|. If |leftRight| is true then the left-right diff is used for ordered sequences - see Diff vs DiffLeftRight in Set and Map.

func Summary ¶

func Summary(value1, value2 types.Value)

Summary prints a summary of the diff between two values to stdout.