From 8e2c38b977a379e4b9a35101db91f7978ef641bc Mon Sep 17 00:00:00 2001
From: Chris H-C <chutten@mozilla.com>
Date: Tue, 11 Jan 2022 16:41:23 -0500
Subject: [PATCH] bug 1745283 Support file-level tags

---
 CHANGELOG.md                                   |  2 ++
 glean_parser/parser.py                         |  6 ++++++
 glean_parser/schemas/metrics.2-0-0.schema.yaml | 10 +++++++++-
 tests/data/metric-with-tags.yaml               |  3 +++
 tests/data/tags.yaml                           |  5 +++++
 tests/test_parser.py                           | 11 +++++++----
 6 files changed, 32 insertions(+), 5 deletions(-)

diff --git a/CHANGELOG.md b/CHANGELOG.md
index a067f13f..2ad5d7cf 100644
--- a/CHANGELOG.md
+++ b/CHANGELOG.md
@@ -2,6 +2,8 @@
 
 ## Unreleased
 
+- Support global file-level tags in metrics.yaml ([bug 1745283](https://bugzilla.mozilla.org/show_bug.cgi?id=1745283))
+
 ## 4.3.1
 
 - BUGFIX: Skip tags for code generation ([#409](https://github.com/mozilla/glean_parser/pull/409))
diff --git a/glean_parser/parser.py b/glean_parser/parser.py
index 7d8db00e..a6afb7d3 100644
--- a/glean_parser/parser.py
+++ b/glean_parser/parser.py
@@ -195,6 +195,8 @@ def _instantiate_metrics(
     objects, and merge them into a single tree.
     """
     global_no_lint = content.get("no_lint", [])
+    global_tags = content.get("$tags", [])
+    assert isinstance(global_tags, list)
 
     for category_key, category_val in content.items():
         if category_key.startswith("$"):
@@ -243,6 +245,10 @@ def _instantiate_metrics(
 
             if metric_obj is not None:
                 metric_obj.no_lint = list(set(metric_obj.no_lint + global_no_lint))
+                if len(global_tags):
+                    metric_obj.metadata["tags"] = list(
+                        set(metric_obj.metadata.get("tags", []) + global_tags)
+                    )
 
                 if isinstance(filepath, Path):
                     metric_obj.defined_in["filepath"] = str(filepath)
diff --git a/glean_parser/schemas/metrics.2-0-0.schema.yaml b/glean_parser/schemas/metrics.2-0-0.schema.yaml
index 37000ec9..eb2644a9 100644
--- a/glean_parser/schemas/metrics.2-0-0.schema.yaml
+++ b/glean_parser/schemas/metrics.2-0-0.schema.yaml
@@ -538,7 +538,7 @@ propertyNames:
         - not:
             description: "'tags' is reserved as a category name."
             const: tags
-    - enum: ['$schema']
+    - enum: ['$schema', '$tags']
 
 properties:
   $schema:
@@ -553,6 +553,14 @@ properties:
     items:
       type: string
 
+  $tags:
+    title: Tags that apply to the whole file
+    description: |
+      This denotes the list of tags that apply to all metrics in this file.
+    type: array
+    items:
+      type: string
+
 additionalProperties:
   type: object
   propertyNames:
diff --git a/tests/data/metric-with-tags.yaml b/tests/data/metric-with-tags.yaml
index a3dfea46..7cb20d40 100644
--- a/tests/data/metric-with-tags.yaml
+++ b/tests/data/metric-with-tags.yaml
@@ -4,6 +4,9 @@
 ---
 $schema: moz://mozilla.org/schemas/glean/metrics/2-0-0
 
+$tags:
+  - global_tag
+
 telemetry:
   client_id:
     type: uuid
diff --git a/tests/data/tags.yaml b/tests/data/tags.yaml
index ba66eef9..e05eb9ff 100644
--- a/tests/data/tags.yaml
+++ b/tests/data/tags.yaml
@@ -13,3 +13,8 @@ apple:
   description: |
     A red fruit. Or green. Or a mix of it.
     Very good in pie.
+
+global_tag:
+  description: |
+    A very uninteresting global tag.
+    Alas, it has no colour.
diff --git a/tests/test_parser.py b/tests/test_parser.py
index 0101f41a..acecef83 100644
--- a/tests/test_parser.py
+++ b/tests/test_parser.py
@@ -110,7 +110,7 @@ def test_parser_schema_violation():
         the given schemas
         'gleantest.with.way.too.long.category.name' is too long
         'gleantest.with.way.too.long.category.name' is not one of
-        ['$schema']
+        ['$schema', '$tags']
         """,
         """
         ```
@@ -569,9 +569,12 @@ def test_tags():
 
     assert errors == []
     assert len(all_metrics.value) == 1
-    assert all_metrics.value["telemetry"]["client_id"].metadata == {
-        "tags": ["banana", "apple"]
-    }
+    assert set(all_metrics.value["telemetry"]["client_id"].metadata.keys()) == set(
+        ["tags"]
+    )
+    assert set(all_metrics.value["telemetry"]["client_id"].metadata["tags"]) == set(
+        ["banana", "apple", "global_tag"]
+    )
 
 
 def test_custom_expires():