New option: csv-diff one.csv two.csv --json

Author: simonw

csv_diff/__init__.py

@@ -23,35 +23,56 @@ def compare(previous, current):
     removed_or_added = set(removed) | set(added)
     potential_changes = [id for id in current if id not in removed_or_added]
     changed = [id for id in potential_changes if current[id] != previous[id]]
-    # Now generate the readable summary
-    summary = []
-    title = []
+    result = {"added": [], "removed": [], "changed": []}
     if added:
-        fragment = "{} row{} added".format(len(added), "" if len(added) == 1 else "s")
+        result["added"] = [current[id] for id in added]
+    if removed:
+        result["removed"] = [previous[id] for id in removed]
+    if changed:
+        for id in changed:
+            d = list(diff(previous[id], current[id]))
+            result["changed"].append(
+                {
+                    "key": id,
+                    "changes": {
+                        field: [prev_value, current_value]
+                        for _, field, (prev_value, current_value) in d
+                    },
+                }
+            )
+    return result
+
+
+def human_text(result):
+    title = []
+    summary = []
+    if result["added"]:
+        fragment = "{} row{} added".format(
+            len(result["added"]), "" if len(result["added"]) == 1 else "s"
+        )
         title.append(fragment)
         summary.append(fragment + "\n")
-        for id in added:
-            summary.append("  {}".format(json.dumps(current[id])))
+        for row in result["added"]:
+            summary.append("  {}".format(json.dumps(row)))
         summary.append("")
-    if removed:
+    if result["removed"]:
         fragment = "{} row{} removed".format(
-            len(removed), "" if len(removed) == 1 else "s"
+            len(result["removed"]), "" if len(result["removed"]) == 1 else "s"
         )
         title.append(fragment)
         summary.append(fragment + "\n")
-        for id in removed:
-            summary.append("  {}".format(json.dumps(previous[id])))
+        for row in result["removed"]:
+            summary.append("  {}".format(json.dumps(row)))
         summary.append("")
-    if changed:
+    if result["changed"]:
         fragment = "{} row{} changed".format(
-            len(changed), "" if len(changed) == 1 else "s"
+            len(result["changed"]), "" if len(result["changed"]) == 1 else "s"
         )
         title.append(fragment)
         summary.append(fragment + "\n")
-        for id in changed:
-            d = list(diff(previous[id], current[id]))
-            summary.append("  Row {}".format(id))
-            for _, field, (prev_value, current_value) in d:
+        for details in result["changed"]:
+            summary.append("  Row {}".format(details["key"]))
+            for field, (prev_value, current_value) in details["changes"].items():
                 summary.append(
                     '    {}: "{}" => "{}"'.format(field, prev_value, current_value)
                 )

csv_diff/cli.py

@@ -1,5 +1,6 @@
 import click
-from . import load_csv, compare
+import json as std_json
+from . import load_csv, compare, human_text
 
 
 @click.command()
@@ -15,6 +16,13 @@
 @click.option(
     "--key", type=str, default=None, help="Column to use as a unique ID for each row"
 )
-def cli(previous, current, key):
+@click.option(
+    "--json", type=bool, default=False, help="Output changes as JSON", is_flag=True
+)
+def cli(previous, current, key, json):
     "Diff two CSV files"
-    print(compare(load_csv(open(previous), key=key), load_csv(open(current), key=key)))
+    diff = compare(load_csv(open(previous), key=key), load_csv(open(current), key=key))
+    if json:
+        print(std_json.dumps(diff, indent=4))
+    else:
+        print(human_text(diff))

tests/test_cli.py

@@ -0,0 +1,31 @@
+from click.testing import CliRunner
+from csv_diff import cli
+from .test_csv_diff import ONE, TWO, THREE
+import json
+
+
+def test_human_cli(tmpdir):
+    one = tmpdir / "one.csv"
+    one.write(ONE)
+    two = tmpdir / "two.csv"
+    two.write(TWO)
+    result = CliRunner().invoke(cli.cli, [str(one), str(two), "--key", "id"])
+    assert 0 == result.exit_code
+    assert (
+        '1 row changed\n\n1 row changed\n\n  Row 1\n    age: "4" => "5"'
+        == result.output.strip()
+    )
+
+
+def test_human_cli_json(tmpdir):
+    one = tmpdir / "one.csv"
+    one.write(ONE)
+    two = tmpdir / "two.csv"
+    two.write(TWO)
+    result = CliRunner().invoke(cli.cli, [str(one), str(two), "--key", "id", "--json"])
+    assert 0 == result.exit_code
+    assert {
+        "added": [],
+        "removed": [],
+        "changed": [{"key": "1", "changes": {"age": ["4", "5"]}}],
+    } == json.loads(result.output.strip())

tests/test_csv_diff.py

@@ -9,9 +9,38 @@
 1,Cleo,5
 2,Pancakes,2"""
 
+THREE = """id,name,age
+1,Cleo,5"""
 
-def test_diff():
+
+def test_row_changed():
     diff = compare(
         load_csv(io.StringIO(ONE), key="id"), load_csv(io.StringIO(TWO), key="id")
     )
-    assert '1 row changed\n\n1 row changed\n\n  Row 1\n    age: "4" => "5"' == diff
+    assert {
+        "added": [],
+        "removed": [],
+        "changed": [{"key": "1", "changes": {"age": ["4", "5"]}}],
+    } == diff
+
+
+def test_row_added():
+    diff = compare(
+        load_csv(io.StringIO(THREE), key="id"), load_csv(io.StringIO(TWO), key="id")
+    )
+    assert {
+        "changed": [],
+        "removed": [],
+        "added": [{"age": "2", "id": "2", "name": "Pancakes"}],
+    } == diff
+
+
+def test_row_removed():
+    diff = compare(
+        load_csv(io.StringIO(TWO), key="id"), load_csv(io.StringIO(THREE), key="id")
+    )
+    assert {
+        "changed": [],
+        "removed": [{"age": "2", "id": "2", "name": "Pancakes"}],
+        "added": [],
+    } == diff

tests/test_human_text.py

@@ -0,0 +1,33 @@
+from csv_diff import load_csv, compare, human_text
+from .test_csv_diff import ONE, TWO, THREE
+import io
+
+
+def test_row_changed():
+    diff = compare(
+        load_csv(io.StringIO(ONE), key="id"), load_csv(io.StringIO(TWO), key="id")
+    )
+    assert (
+        '1 row changed\n\n1 row changed\n\n  Row 1\n    age: "4" => "5"'
+        == human_text(diff)
+    )
+
+
+def test_row_added():
+    diff = compare(
+        load_csv(io.StringIO(THREE), key="id"), load_csv(io.StringIO(TWO), key="id")
+    )
+    assert (
+        '1 row added\n\n1 row added\n\n  {"id": "2", "name": "Pancakes", "age": "2"}'
+        == human_text(diff)
+    )
+
+
+def test_row_removed():
+    diff = compare(
+        load_csv(io.StringIO(TWO), key="id"), load_csv(io.StringIO(THREE), key="id")
+    )
+    assert (
+        '1 row removed\n\n1 row removed\n\n  {"id": "2", "name": "Pancakes", "age": "2"}'
+        == human_text(diff)
+    )