## backends.ObjectDiff


What changed inside one object between two recorded states.


Usage

``` python
backends.ObjectDiff(
    unit="entries",
    added=0,
    removed=0,
    modified=0,
    entries=list(),
    truncated=False,
    note=""
)
```


Backends describe changes at whatever granularity their system exposes natively and cheaply (files, tables, arrays, fragments, versions); [unit](testing.ObjectDiff.md#tether.testing.ObjectDiff.unit) names it. Entries are capped at [MAX_DIFF_ENTRIES](backends.MAX_DIFF_ENTRIES.md#tether.backends.MAX_DIFF_ENTRIES); counts are not.


## Parameter Attributes


`unit: str = ``"entries"`  
What is being counted: files, tables, arrays, fragments, commits, …

`added: int = ``0`  
Exact count of added units.

`removed: int = ``0`  
Exact count of removed units.

`modified: int = ``0`  
Exact count of modified (or renamed) units.

`entries: list[ChangeEntry] = list()`  
Per-unit entries, capped at [MAX_DIFF_ENTRIES](backends.MAX_DIFF_ENTRIES.md#tether.backends.MAX_DIFF_ENTRIES).

`truncated: bool = ``False`  
Whether entries were dropped because of the cap.

`note: str = ``""`  
Context the counts alone do not convey (e.g. a missing listing).


## Attributes

| Name | Description |
|----|----|
| [is_empty](#is_empty) | `True` when nothing changed. |
| [summary](#summary) | One line: `"+A -R ~M <unit>"` plus truncation and note. |

------------------------------------------------------------------------


#### is_empty


`True` when nothing changed.


`is_empty: bool`


------------------------------------------------------------------------


#### summary


One line: `"+A -R ~M <unit>"` plus truncation and note.


`summary: str`


## Methods

| Name | Description |
|----|----|
| [add()](#add) | Record one change: bump the matching counter and append an entry. |

------------------------------------------------------------------------


#### add()


Record one change: bump the matching counter and append an entry.


Usage

``` python
add(path, change, detail="")
```