metrics: introduce diff

dvc/command/metrics.py

@@ -26,7 +26,12 @@ def show_metrics(metrics, all_branches=False, all_tags=False):
             logger.info("{branch}:".format(branch=branch))
 
         for fname, metric in val.items():
-            lines = metric if type(metric) is list else metric.splitlines()
+            if isinstance(metric, dict):
+                lines = list(metric.values())
+            elif isinstance(metric, list):
+                lines = metric
+            else:
+                lines = metric.splitlines()
 
             if len(lines) > 1:
                 logger.info("\t{fname}:".format(fname=fname))
@@ -100,6 +105,59 @@ def run(self):
         return 0
 
 
+def _show_diff(diff):
+    from texttable import Texttable
+
+    if not diff:
+        return "No changes."
+
+    table = Texttable()
+
+    # remove borders to make it easier for users to copy stuff
+    table.set_chars(("", "", "", ""))
+    table.set_deco(0)
+
+    rows = [["Path", "Metric", "Value", "Change"]]
+    for fname, mdiff in diff.items():
+        for metric, change in mdiff.items():
+            rows.append(
+                [
+                    fname,
+                    metric,
+                    change["new"],
+                    change.get("diff", "diff not supported"),
+                ]
+            )
+    table.add_rows(rows)
+    return table.draw()
+
+
+class CmdMetricsDiff(CmdBase):
+    def run(self):
+        try:
+            diff = self.repo.metrics.diff(
+                a_ref=self.args.a_ref,
+                b_ref=self.args.b_ref,
+                targets=self.args.targets,
+                typ=self.args.type,
+                xpath=self.args.xpath,
+                recursive=self.args.recursive,
+            )
+
+            if self.args.show_json:
+                import json
+
+                logger.info(json.dumps(diff))
+            else:
+                logger.info(_show_diff(diff))
+
+        except DvcException:
+            logger.exception("failed to show metrics diff")
+            return 1
+
+        return 0
+
+
 def add_parser(subparsers, parent_parser):
     METRICS_HELP = "Commands to add, manage, collect and display metrics."
 
@@ -214,3 +272,65 @@ def add_parser(subparsers, parent_parser):
     )
     metrics_remove_parser.add_argument("path", help="Path to a metric file.")
     metrics_remove_parser.set_defaults(func=CmdMetricsRemove)
+
+    METRICS_DIFF_HELP = "Output metric values."
+    metrics_diff_parser = metrics_subparsers.add_parser(
+        "diff",
+        parents=[parent_parser],
+        description=append_doc_link(METRICS_DIFF_HELP, "metrics/diff"),
+        help=METRICS_DIFF_HELP,
+        formatter_class=argparse.RawDescriptionHelpFormatter,
+    )
+    metrics_diff_parser.add_argument(
+        "a_ref",
+        nargs="?",
+        help=(
+            "Git reference from which diff is calculated. "
+            "If omitted `HEAD`(latest commit) is used."
+        ),
+    )
+    metrics_diff_parser.add_argument(
+        "b_ref",
+        nargs="?",
+        help=(
+            "Git reference to which diff is calculated. "
+            "If omitted current working tree is used."
+        ),
+    )
+    metrics_diff_parser.add_argument(
+        "--targets",
+        nargs="*",
+        help=(
+            "Metric files or directories (see -R) to show diff for. "
+            "Shows diff for all metric files by default."
+        ),
+    )
+    metrics_diff_parser.add_argument(
+        "-t",
+        "--type",
+        help=(
+            "Type of metrics (json/tsv/htsv/csv/hcsv). "
+            "It can be detected by the file extension automatically. "
+            "Unsupported types will be treated as raw."
+        ),
+    )
+    metrics_diff_parser.add_argument(
+        "-x", "--xpath", help="json/tsv/htsv/csv/hcsv path."
+    )
+    metrics_diff_parser.add_argument(
+        "-R",
+        "--recursive",
+        action="store_true",
+        default=False,
+        help=(
+            "If any target is a directory, recursively search and process "
+            "metric files."
+        ),
+    )
+    metrics_diff_parser.add_argument(
+        "--show-json",
+        action="store_true",
+        default=False,
+        help="Show output in JSON format.",
+    )
+    metrics_diff_parser.set_defaults(func=CmdMetricsDiff)

dvc/repo/brancher.py

@@ -4,7 +4,7 @@
 
 
 def brancher(  # noqa: E302
-    self, all_branches=False, all_tags=False, all_commits=False
+    self, revs=None, all_branches=False, all_tags=False, all_commits=False
 ):
     """Generator that iterates over specified revisions.
 
@@ -20,12 +20,12 @@ def brancher(  # noqa: E302
             - empty string it there is no branches to iterate over
             - "Working Tree" if there are uncommitted changes in the SCM repo
     """
-    if not any([all_branches, all_tags, all_commits]):
+    if not any([revs, all_branches, all_tags, all_commits]):
         yield ""
         return
 
     saved_tree = self.tree
-    revs = []
+    revs = revs or []
 
     scm = self.scm
 

dvc/repo/metrics/__init__.py

@@ -21,3 +21,8 @@ def remove(self, *args, **kwargs):
         from dvc.repo.metrics.remove import remove
 
         return remove(self.repo, *args, **kwargs)
+
+    def diff(self, *args, **kwargs):
+        from .diff import diff
+
+        return diff(self.repo, *args, **kwargs)

dvc/repo/metrics/diff.py

@@ -0,0 +1,105 @@
+import json
+from collections import defaultdict
+
+from flatten_dict import flatten
+
+from dvc.exceptions import NoMetricsError
+
+
+def _parse(raw):
+    if isinstance(raw, (dict, list, int, float)):
+        return raw
+
+    assert isinstance(raw, str)
+    try:
+        return json.loads(raw)
+    except json.JSONDecodeError:
+        return raw
+
+
+def _diff_vals(old, new):
+    if (
+        isinstance(new, list)
+        and isinstance(old, list)
+        and len(old) == len(new) == 1
+    ):
+        return _diff_vals(old[0], new[0])
+
+    if old == new:
+        return {}
+
+    res = {"old": old, "new": new}
+    if isinstance(new, (int, float)) and isinstance(old, (int, float)):
+        res["diff"] = new - old
+    return res
+
+
+# dot_reducer is not released yet (flatten-dict > 0.2.0)
+def _dot(k1, k2):
+    if k1 is None:
+        return k2
+    return "{0}.{1}".format(k1, k2)
+
+
+def _diff_dicts(old_dict, new_dict):
+    old_default = None
+    new_default = None
+
+    if isinstance(new_dict, dict):
+        new = flatten(new_dict, reducer=_dot)
+    else:
+        new = defaultdict(lambda: "not a dict")
+        new_default = "unable to parse"
+
+    if isinstance(old_dict, dict):
+        old = flatten(old_dict, reducer=_dot)
+    else:
+        old = defaultdict(lambda: "not a dict")
+        old_default = "unable to parse"
+
+    res = defaultdict(dict)
+
+    xpaths = set(old.keys())
+    xpaths.update(set(new.keys()))
+    for xpath in xpaths:
+        old_val = old.get(xpath, old_default)
+        new_val = new.get(xpath, new_default)
+        val_diff = _diff_vals(old_val, new_val)
+        if val_diff:
+            res[xpath] = val_diff
+    return dict(res)
+
+
+def _diff(old_raw, new_raw):
+    old = _parse(old_raw)
+    new = _parse(new_raw)
+
+    if isinstance(new, dict) or isinstance(old, dict):
+        return _diff_dicts(old, new)
+
+    return {"": _diff_vals(old, new)}
+
+
+def _get_metrics(repo, *args, rev=None, **kwargs):
+    try:
+        metrics = repo.metrics.show(
+            *args, **kwargs, revs=[rev] if rev else None
+        )
+        return metrics[rev or ""]
+    except NoMetricsError:
+        return {}
+
+
+def diff(repo, *args, a_ref=None, b_ref=None, **kwargs):
+    old = _get_metrics(repo, *args, **kwargs, rev=(a_ref or "HEAD"))
+    new = _get_metrics(repo, *args, **kwargs, rev=b_ref)
+
+    paths = set(old.keys())
+    paths.update(set(new.keys()))
+
+    res = defaultdict(dict)
+    for path in paths:
+        path_diff = _diff(old[path], new[path])
+        if path_diff:
+            res[path] = path_diff
+    return dict(res)

dvc/repo/metrics/show.py

@@ -20,7 +20,7 @@
 
 def _read_metric_json(fd, json_path):
     parser = parse(json_path)
-    return [x.value for x in parser.find(json.load(fd))]
+    return {str(x.full_path): x.value for x in parser.find(json.load(fd))}
 
 
 def _get_values(row):
@@ -266,6 +266,7 @@ def show(
     all_branches=False,
     all_tags=False,
     recursive=False,
+    revs=None,
 ):
     res = {}
     found = set()
@@ -274,7 +275,9 @@ def show(
         # Iterate once to call `_collect_metrics` on all the stages
         targets = [None]
 
-    for branch in repo.brancher(all_branches=all_branches, all_tags=all_tags):
+    for branch in repo.brancher(
+        revs=revs, all_branches=all_branches, all_tags=all_tags
+    ):
         metrics = {}
 
         for target in targets:

setup.py

@@ -75,6 +75,8 @@ def run(self):
     "win-unicode-console>=0.5; sys_platform == 'win32'",
     "pywin32>=225; sys_platform == 'win32'",
     "networkx>=2.1,<2.4",
+    "flatten-dict>=0.2.0",
+    "texttable>=0.5.2",
 ]