fix: address PR review comments for --slack-full-width

- Replace invalid empty rich_text block with valid non-empty structure
  (Slack API rejects empty elements arrays)
- Add max_length param to list_of_dicts_to_markdown_table for graceful
  row-by-row truncation instead of cutting mid-row
- Capitalize "markdown" to "Markdown" in docs (proper noun)
- Run preview validation in full-width mode for consistent safety bounds
- Update tests for valid rich_text block and exact assertions

Made-with: Cursor

Author: haritamar

docs/oss/deployment-and-configuration/slack.mdx

@@ -56,12 +56,12 @@ The alert format is:
 
 ## Full-width alerts
 
-By default, Slack alerts use a narrower layout with some content in attachments. To use the full message width and show test results as a markdown table in the main message body, pass the flag when running the monitor:
+By default, Slack alerts use a narrower layout with some content in attachments. To use the full message width and show test results as a Markdown table in the main message body, pass the flag when running the monitor:
 
 ```shell
 edr monitor --slack-token <your_slack_token> --slack-channel-name <channel> --slack-full-width
 ```
 
-With `--slack-full-width`, alerts are sent using Slack Block Kit in the main message body instead of attachments, so the full channel width is used and test result samples appear as formatted markdown tables.
+With `--slack-full-width`, alerts are sent using Slack Block Kit in the main message body instead of attachments, so the full channel width is used and test result samples appear as formatted Markdown tables.
 
 ---

docs/oss/guides/alerts/send-slack-alerts.mdx

@@ -24,7 +24,7 @@ Make sure to run the following command after your dbt runs and tests:
 edr monitor --slack-token <your_slack_token> --slack-channel-name <slack_channel_to_post_at> --group-by [table | alert]
 ```
 
-Add `--slack-full-width` to use the full message width and show test results as markdown tables. See [Slack setup - Full-width alerts](/oss/deployment-and-configuration/slack#full-width-alerts).
+Add `--slack-full-width` to use the full message width and show test results as Markdown tables. See [Slack setup - Full-width alerts](/oss/deployment-and-configuration/slack#full-width-alerts).
 
 Or just `edr monitor` if you used `config.yml`. Please note that when you specify the --slack-channel-name, it's the
 default channel name to which all the alerts will be sent that are not attributed to any custom channel. Therefore,

elementary/monitor/data_monitoring/alerts/integrations/slack/message_builder.py

@@ -35,9 +35,22 @@ def get_slack_message(
         alert_schema: SlackAlertMessageSchema,
     ) -> SlackMessageSchema:
         if self.full_width:
-            # Empty rich_text block forces Slack to use full message width for following
-            # blocks instead of the narrower attachment-style layout.
-            self._add_always_displayed_blocks([{"type": "rich_text", "elements": []}])
+            # A rich_text block at the start forces Slack to use full message width
+            # for following blocks instead of the narrower attachment-style layout.
+            # The elements array must be non-empty per Slack Block Kit API.
+            self._add_always_displayed_blocks(
+                [
+                    {
+                        "type": "rich_text",
+                        "elements": [
+                            {
+                                "type": "rich_text_section",
+                                "elements": [{"type": "text", "text": " "}],
+                            }
+                        ],
+                    }
+                ]
+            )
         self.add_title_to_slack_alert(alert_schema.title)
         self.add_preview_to_slack_alert(alert_schema.preview)
         self.add_details_to_slack_alert(alert_schema.details)
@@ -55,10 +68,10 @@ def add_preview_to_slack_alert(
     ):
         if not preview_blocks:
             return
+        validated_preview_blocks = self._validate_preview_blocks(preview_blocks)
         if self.full_width:
-            self._add_always_displayed_blocks(preview_blocks)
+            self._add_always_displayed_blocks(validated_preview_blocks)
         else:
-            validated_preview_blocks = self._validate_preview_blocks(preview_blocks)
             self._add_blocks_as_attachments(validated_preview_blocks)
 
     def add_details_to_slack_alert(

elementary/monitor/data_monitoring/alerts/integrations/slack/slack.py

@@ -222,8 +222,9 @@ def _get_dbt_test_template(
             TEST_RESULTS_SAMPLE_FIELD in (alert.alert_fields or DEFAULT_ALERT_FIELDS)
             and alert.test_rows_sample
         ):
+            table_max_length = SectionBlock.text_max_length - 6
             test_rows_sample_table = list_of_dicts_to_markdown_table(
-                alert.test_rows_sample
+                alert.test_rows_sample, max_length=table_max_length
             )
             result.extend(
                 [

elementary/utils/json_utils.py

@@ -112,12 +112,17 @@ def _format_value(value: Any) -> str:
     return str(value)
 
 
-def list_of_dicts_to_markdown_table(data: List[Dict[str, Any]]) -> str:
+def list_of_dicts_to_markdown_table(
+    data: List[Dict[str, Any]], max_length: Optional[int] = None
+) -> str:
     """
     Convert a list of dictionaries with consistent keys to a markdown table string.
 
     Args:
         data: List of dictionaries
+        max_length: Optional maximum character length for the output. If the full
+            table exceeds this limit, rows are removed from the end and a
+            "(truncated)" note is appended to avoid cutting mid-row.
 
     Returns:
         A markdown-formatted table string using GitHub table format
@@ -126,6 +131,31 @@ def list_of_dicts_to_markdown_table(data: List[Dict[str, Any]]) -> str:
         return ""
 
     processed_data = [{k: _format_value(v) for k, v in row.items()} for row in data]
-    return tabulate(
+    full_table = tabulate(
         processed_data, headers="keys", tablefmt="github", disable_numparse=True
     )
+
+    if max_length is None or len(full_table) <= max_length:
+        return full_table
+
+    truncation_note = "\n(truncated)"
+    effective_max = max_length - len(truncation_note)
+    for row_count in range(len(processed_data) - 1, 0, -1):
+        table = tabulate(
+            processed_data[:row_count],
+            headers="keys",
+            tablefmt="github",
+            disable_numparse=True,
+        )
+        if len(table) <= effective_max:
+            return table + truncation_note
+
+    single_row_table = tabulate(
+        processed_data[:1],
+        headers="keys",
+        tablefmt="github",
+        disable_numparse=True,
+    )
+    if effective_max <= 0 or len(single_row_table) <= effective_max:
+        return single_row_table + truncation_note
+    return single_row_table[:effective_max].rstrip() + truncation_note

tests/unit/monitor/data_monitoring/alerts/integrations/slack/test_slack_alert_message_builder.py

@@ -177,11 +177,11 @@ def test_add_details_to_slack_alert():
 
 
 def test_full_width_preview_goes_to_blocks_not_attachments():
-    """With full_width=True, preview blocks are added to main blocks."""
+    """With full_width=True, preview blocks are validated and added to main blocks."""
     message_builder = SlackAlertMessageBuilder(full_width=True)
     block = message_builder.create_header_block("Preview header")
     message_builder.add_preview_to_slack_alert([block])
-    assert len(message_builder.slack_message["blocks"]) == 1
+    assert len(message_builder.slack_message["blocks"]) == 5
     assert message_builder.slack_message["blocks"][0] == block
     assert message_builder.slack_message["attachments"][0]["blocks"] == []
 
@@ -210,11 +210,21 @@ def test_full_width_get_slack_message_structure():
     result = message_builder.get_slack_message(alert_schema=schema)
 
     blocks = result.blocks
-    assert len(blocks) >= 5
-    assert blocks[0] == {"type": "rich_text", "elements": []}
+    valid_rich_text_block = {
+        "type": "rich_text",
+        "elements": [
+            {
+                "type": "rich_text_section",
+                "elements": [{"type": "text", "text": " "}],
+            }
+        ],
+    }
+    assert blocks[0] == valid_rich_text_block
     assert blocks[1] == title
     assert blocks[2]["type"] == "divider"
     assert blocks[3] == preview_block
-    assert blocks[4] == detail_block
+    # Blocks 4-7 are padding from preview validation
+    assert blocks[8] == detail_block
+    assert len(blocks) == 9
 
     assert result.attachments == []