server/tags: add tag merging

API.md

@@ -25,6 +25,7 @@
         - [Updating tag](#updating-tag)
         - [Getting tag](#getting-tag)
         - [Deleting tag](#deleting-tag)
+        - [Merging tags](#merging-tags)
     - Users
         - [Listing users](#listing-users)
         - [Creating user](#creating-user)
@@ -508,6 +509,49 @@ data.
     Deletes existing tag. The tag to be deleted must have no usages.
 
 
+## Merging tags
+- **Request**
+
+    `POST /tag-merge/`
+
+- **Input**
+
+    ```json5
+    {
+        "remove": "source-tag",
+        "merge-to": "target-tag"
+    }
+    ```
+
+- **Output**
+
+    ```json5
+    {
+        "tag": <tag>,
+        "snapshots": [
+            {"data": <tag-snapshot>, "time": <snapshot-time>},
+            {"data": <tag-snapshot>, "time": <snapshot-time>},
+            {"data": <tag-snapshot>, "time": <snapshot-time>}
+        ]
+    }
+    ```
+    ...where `<tag>` is the target [tag resource](#tag), and `snapshots`
+    contain its earlier versions.
+
+- **Errors**
+
+    - the source or target tag does not exist
+    - the source tag is the same as the target tag
+    - privileges are too low
+
+- **Description**
+
+    Removes source tag and merges all of its usages to the target tag. Source
+    tag properties such as category, tag relations etc. do not get transferred
+    and are discarded. The target tag effectively remains unchanged with the
+    exception of the set of posts it's used in.
+
+
 ## Listing users
 - **Request**
 

server/szurubooru/api/__init__.py

@@ -2,6 +2,6 @@
 
 from szurubooru.api.password_reset_api import PasswordResetApi
 from szurubooru.api.user_api import UserListApi, UserDetailApi
-from szurubooru.api.tag_api import TagListApi, TagDetailApi
+from szurubooru.api.tag_api import TagListApi, TagDetailApi, TagMergingApi
 from szurubooru.api.tag_category_api import TagCategoryListApi, TagCategoryDetailApi
 from szurubooru.api.context import Context, Request

server/szurubooru/api/tag_api.py

@@ -109,3 +109,25 @@ class TagDetailApi(BaseApi):
         ctx.session.commit()
         tags.export_to_json()
         return {}
+
+class TagMergingApi(BaseApi):
+    def post(self, ctx):
+        source_tag_name = ctx.get_param_as_string('remove', required=True) or ''
+        target_tag_name = ctx.get_param_as_string('merge-to', required=True) or ''
+        source_tag = tags.get_tag_by_name(source_tag_name)
+        target_tag = tags.get_tag_by_name(target_tag_name)
+        if not source_tag:
+            raise tags.TagNotFoundError(
+                'Source tag %r not found.' % source_tag_name)
+        if not target_tag:
+            raise tags.TagNotFoundError(
+                'Source tag %r not found.' % target_tag_name)
+        if source_tag.tag_id == target_tag.tag_id:
+            raise tags.InvalidTagRelationError(
+                'Cannot merge tag with itself.')
+        auth.verify_privilege(ctx.user, 'tags:merge')
+        tags.merge_tags(source_tag, target_tag)
+        snapshots.delete(source_tag, ctx.user)
+        ctx.session.commit()
+        tags.export_to_json()
+        return _serialize_tag_with_details(target_tag)

server/szurubooru/app.py

@@ -53,6 +53,7 @@ def create_app():
     tag_category_detail_api = api.TagCategoryDetailApi()
     tag_list_api = api.TagListApi()
     tag_detail_api = api.TagDetailApi()
+    tag_merging_api = api.TagMergingApi()
     password_reset_api = api.PasswordResetApi()
 
     app.add_error_handler(errors.AuthError, _on_auth_error)
@@ -68,6 +69,7 @@ def create_app():
     app.add_route('/tag-category/{category_name}', tag_category_detail_api)
     app.add_route('/tags/', tag_list_api)
     app.add_route('/tag/{tag_name}', tag_detail_api)
+    app.add_route('/tag-merge/', tag_merging_api)
     app.add_route('/password-reset/{user_name}', password_reset_api)
 
     return app

server/szurubooru/func/tags.py

@@ -98,6 +98,13 @@ def get_or_create_tags_by_names(names):
             new_tags.append(new_tag)
     return related_tags, new_tags
 
+def merge_tags(source_tag, target_tag):
+    db.session.execute(
+        sqlalchemy.sql.expression.update(db.PostTag) \
+            .where(db.PostTag.tag_id == source_tag.tag_id) \
+            .values(tag_id=target_tag.tag_id))
+    db.session.delete(source_tag)
+
 def create_tag(names, category_name, suggestions, implications):
     tag = db.Tag()
     tag.creation_time = datetime.datetime.now()

server/szurubooru/tests/api/test_tag_merging.py

@@ -0,0 +1,168 @@
+import datetime
+import os
+import pytest
+from szurubooru import api, config, db, errors
+from szurubooru.func import util, tags
+
+def get_tag(name):
+    return db.session \
+        .query(db.Tag) \
+        .join(db.TagName) \
+        .filter(db.TagName.name==name) \
+        .first()
+
+@pytest.fixture
+def test_ctx(
+        tmpdir, config_injector, context_factory, user_factory, tag_factory):
+    config_injector({
+        'data_dir': str(tmpdir),
+        'ranks': ['anonymous', 'regular_user'],
+        'privileges': {
+            'tags:merge': 'regular_user',
+        },
+    })
+    ret = util.dotdict()
+    ret.context_factory = context_factory
+    ret.user_factory = user_factory
+    ret.tag_factory = tag_factory
+    ret.api = api.TagMergingApi()
+    return ret
+
+def test_merging_without_usages(test_ctx, fake_datetime):
+    source_tag = test_ctx.tag_factory(names=['source'], category_name='meta')
+    target_tag = test_ctx.tag_factory(names=['target'], category_name='meta')
+    db.session.add_all([source_tag, target_tag])
+    db.session.commit()
+    with fake_datetime('1997-12-01'):
+        result = test_ctx.api.post(
+            test_ctx.context_factory(
+                input={
+                    'remove': 'source',
+                    'merge-to': 'target',
+                },
+                user=test_ctx.user_factory(rank='regular_user')))
+    assert result['tag'] == {
+        'names': ['target'],
+        'category': 'meta',
+        'suggestions': [],
+        'implications': [],
+        'creationTime': datetime.datetime(1996, 1, 1),
+        'lastEditTime': None,
+    }
+    assert 'snapshots' in result
+    assert get_tag('source') is None
+    tag = get_tag('target')
+    assert tag is not None
+    assert os.path.exists(os.path.join(config.config['data_dir'], 'tags.json'))
+
+def test_merging_with_usages(test_ctx, fake_datetime, post_factory):
+    source_tag = test_ctx.tag_factory(names=['source'], category_name='meta')
+    target_tag = test_ctx.tag_factory(names=['target'], category_name='meta')
+    db.session.add_all([source_tag, target_tag])
+    db.session.flush()
+    assert source_tag.post_count == 0
+    assert target_tag.post_count == 0
+    post = post_factory()
+    post.tags = [source_tag]
+    db.session.add(post)
+    db.session.commit()
+    assert source_tag.post_count == 1
+    assert target_tag.post_count == 0
+    with fake_datetime('1997-12-01'):
+        result = test_ctx.api.post(
+            test_ctx.context_factory(
+                input={
+                    'remove': 'source',
+                    'merge-to': 'target',
+                },
+                user=test_ctx.user_factory(rank='regular_user')))
+    assert get_tag('source') is None
+    assert get_tag('target').post_count == 1
+
+@pytest.mark.parametrize('input,expected_exception', [
+    ({'remove': None}, tags.TagNotFoundError),
+    ({'remove': ''}, tags.TagNotFoundError),
+    ({'remove': []}, tags.TagNotFoundError),
+    ({'merge-to': None}, tags.TagNotFoundError),
+    ({'merge-to': ''}, tags.TagNotFoundError),
+    ({'merge-to': []}, tags.TagNotFoundError),
+])
+def test_trying_to_pass_invalid_input(test_ctx, input, expected_exception):
+    source_tag = test_ctx.tag_factory(names=['source'], category_name='meta')
+    target_tag = test_ctx.tag_factory(names=['target'], category_name='meta')
+    db.session.add_all([source_tag, target_tag])
+    db.session.commit()
+    real_input = {
+        'remove': 'source',
+        'merge-to': 'target',
+    }
+    for key, value in input.items():
+        real_input[key] = value
+    with pytest.raises(expected_exception):
+        test_ctx.api.post(
+            test_ctx.context_factory(
+                input=real_input,
+                user=test_ctx.user_factory(rank='regular_user')))
+
+@pytest.mark.parametrize(
+    'field', ['remove', 'merge-to'])
+def test_trying_to_omit_mandatory_field(test_ctx, tmpdir, field):
+    db.session.add_all([
+        test_ctx.tag_factory(names=['source'], category_name='meta'),
+        test_ctx.tag_factory(names=['target'], category_name='meta'),
+    ])
+    db.session.commit()
+    input = {
+        'remove': 'source',
+        'merge-to': 'target',
+    }
+    del input[field]
+    with pytest.raises(errors.ValidationError):
+        test_ctx.api.post(
+            test_ctx.context_factory(
+                input=input,
+                user=test_ctx.user_factory(rank='regular_user')))
+
+def test_trying_to_merge_non_existing(test_ctx):
+    db.session.add(test_ctx.tag_factory(names=['good'], category_name='meta'))
+    db.session.commit()
+    with pytest.raises(tags.TagNotFoundError):
+        test_ctx.api.post(
+            test_ctx.context_factory(
+                input={'remove': 'good', 'merge-to': 'bad'},
+                user=test_ctx.user_factory(rank='regular_user')))
+    with pytest.raises(tags.TagNotFoundError):
+        test_ctx.api.post(
+            test_ctx.context_factory(
+                input={'remove': 'bad', 'merge-to': 'good'},
+                user=test_ctx.user_factory(rank='regular_user')))
+
+def test_trying_to_merge_to_itself(test_ctx):
+    db.session.add(test_ctx.tag_factory(names=['good'], category_name='meta'))
+    db.session.commit()
+    with pytest.raises(tags.InvalidTagRelationError):
+        test_ctx.api.post(
+            test_ctx.context_factory(
+                input={'remove': 'good', 'merge-to': 'good'},
+                user=test_ctx.user_factory(rank='regular_user')))
+
+@pytest.mark.parametrize('input', [
+    {'names': 'whatever'},
+    {'category': 'whatever'},
+    {'suggestions': ['whatever']},
+    {'implications': ['whatever']},
+])
+def test_trying_to_merge_without_privileges(test_ctx, input):
+    db.session.add_all([
+        test_ctx.tag_factory(names=['source'], category_name='meta'),
+        test_ctx.tag_factory(names=['target'], category_name='meta'),
+    ])
+    db.session.commit()
+    with pytest.raises(errors.AuthError):
+        test_ctx.api.post(
+            test_ctx.context_factory(
+                input={
+                    'remove': 'source',
+                    'merge-to': 'target',
+                },
+                user=test_ctx.user_factory(rank='anonymous')))