snapshot of https://github.com/zulip/zulip.git @ 48c69911c7dd4e03b20552eb3bd77ad8151c1357 (2026-09-15)

zerver/webhooks/slack_incoming/doc.md

@@ -0,0 +1,37 @@
+# Zulip's Slack-compatible incoming webhook
+
+Zulip can process incoming webhook messages written to work with Slack's
+[incoming webhook API][1]. This makes it easy to quickly move your
+integrations when migrating your organization from Slack to Zulip.
+
+!!! warn ""
+
+     **Note:** In the long term, the recommended approach is to use
+     Zulip's native integrations, which take advantage of Zulip's topics.
+     There may also be some quirks when Slack's formatting system is
+     translated into Zulip's.
+
+{start_tabs}
+
+1. {!create-an-incoming-webhook.md!}
+
+1. {!generate-webhook-url-basic.md!}
+
+1. Use the generated URL anywhere you would use a Slack webhook.
+
+{end_tabs}
+
+### Related documentation
+
+- [Slack's incoming webhook documentation][1]
+
+- [Moving from Slack to Zulip](/help/moving-from-slack)
+
+- [Forward Slack messages into Zulip](/integrations/slack)
+
+- [Forward messages Slack <-> Zulip][2] (both directions)
+
+{!webhooks-url-specification.md!}
+
+[1]: https://api.slack.com/messaging/webhooks
+[2]: https://github.com/zulip/python-zulip-api/blob/main/zulip/integrations/bridge_with_slack/README.md

zerver/webhooks/slack_incoming/fixtures/actions.json

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+{
+  "channel": "C1H9RESGL",
+  "blocks": [
+    {
+      "type": "section",
+      "text": {
+        "type": "mrkdwn",
+        "text": "Danny Torrence left the following _review_ for your property:"
+      }
+    },
+    {
+      "type": "section",
+      "block_id": "section567",
+      "text": {
+        "type": "mrkdwn",
+        "text": "<https://google.com|Overlook Hotel> \n :star: \n Doors had too many axe holes, guest in room 237 was far too rowdy, whole place felt stuck in the 1920s."
+      },
+      "accessory": {
+        "type": "image",
+        "image_url": "https://is5-ssl.mzstatic.com/image/thumb/Purple3/v4/d3/72/5c/d3725c8f-c642-5d69-1904-aa36e4297885/source/256x256bb.jpg",
+        "alt_text": "Haunted hotel image"
+      }
+    },
+    {
+      "type": "section",
+      "block_id": "section789",
+      "fields": [
+        {
+          "type": "mrkdwn",
+          "text": "*Average Rating*\n1.0"
+        }
+      ]
+    },
+    {
+      "type": "actions",
+      "elements": [
+        {
+          "type": "button",
+            "text": {
+                "type": "plain_text",
+                "text": "Reply to review",
+                "emoji": false
+            }
+        }
+      ]
+    }
+  ]
+}

zerver/webhooks/slack_incoming/fixtures/attachment.json

@@ -0,0 +1,21 @@
+{
+    "channel": "#prometheus-alerts",
+    "username": "Alertmanager",
+    "blocks": null,
+    "attachments": [
+        {
+            "title": "[FIRING:2] InstanceDown for api-server (env=\"prod\", severity=\"critical\")",
+            "title_link": "https://alertmanager.local//#/alerts?receiver=default",
+            "text": ":chart_with_upwards_trend: *<http://generator.local/1|Graph>*   :notebook: *<https://runbook.local/1|Runbook>*\n\n*Alert details*:\n*Alert:* api-server down - `critical`\n*Description:* api-server at 1.2.3.4:8080 couldn't be scraped *Details:*\n   • *alertname:* `InstanceDown`\n   • *env:* `prod`\n   • *instance:* `1.2.3.4:8080`\n   • *job:* `api-server`\n   • *severity:* `critical`\n\n*Alert:* api-server down - `critical`\n*Description:* api-server at 1.2.3.4:8081 couldn't be scraped *Details:*\n   • *alertname:* `InstanceDown`\n   • *env:* `prod`\n   • *instance:* `1.2.3.4:8081`\n   • *job:* `api-server`\n   • *severity:* `critical`\n  \n",
+            "fallback": "[FIRING:2] InstanceDown api-server (prod critical) | https://alertmanager.local//#/alerts?receiver=default",
+            "callback_id": "",
+            "footer": "",
+            "color": "danger",
+            "mrkdwn_in": [
+                "fallback",
+                "pretext",
+                "text"
+            ]
+        }
+    ]
+}

zerver/webhooks/slack_incoming/fixtures/attachment_blocks.json

@@ -0,0 +1,67 @@
+{
+  "attachments": [
+    {
+      "blocks": [
+        {
+          "type": "section",
+          "text": {
+            "type": "mrkdwn",
+            "text": "This is a section block with an accessory image."
+          },
+          "accessory": {
+            "type": "image",
+            "image_url": "https://pbs.twimg.com/profile_images/625633822235693056/lNGUneLX_400x400.jpg",
+            "alt_text": "cute cat"
+          }
+        },
+        {
+          "type": "section",
+          "text": {
+            "type": "mrkdwn",
+            "text": "This is a section block with a button."
+          },
+          "accessory": {
+            "type": "button",
+            "text": {
+              "type": "plain_text",
+              "text": "Click Me",
+              "emoji": true
+            },
+            "value": "click_me_123",
+            "action_id": "button-action"
+          }
+        },
+        {
+          "type": "section",
+          "fields": [
+            {
+              "type": "plain_text",
+              "text": "one",
+              "emoji": true
+            },
+            {
+              "type": "plain_text",
+              "text": "two",
+              "emoji": true
+            },
+            {
+              "type": "plain_text",
+              "text": "three",
+              "emoji": true
+            },
+            {
+              "type": "plain_text",
+              "text": "four",
+              "emoji": true
+            },
+            {
+              "type": "plain_text",
+              "text": "five",
+              "emoji": true
+            }
+          ]
+        }
+      ]
+    }
+  ]
+}

zerver/webhooks/slack_incoming/fixtures/attachment_fields.json

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+{
+  "attachments": [
+    {
+      "color": "good",
+      "fields": [
+        {
+          "title": "Requested by",
+          "value": "Some user",
+          "short": true
+        },
+        {
+          "title": "Duration",
+          "value": "00:02:03",
+          "short": true
+        },
+        {
+          "title": "Build pipeline",
+          "value": "ConsumerAddressModule",
+          "short": true
+        },
+        {
+          "title": "Title with null value",
+          "value": null,
+          "short": true
+        },
+        {
+          "title": "Title without value",
+          "short": true
+        },
+        {
+          "title": null,
+          "value": "Value with null title",
+          "short": true
+        },
+        {
+          "value": "Value without title",
+          "short": true
+        },
+        {
+          "title": null,
+          "value": null,
+          "short": true
+        }
+      ],
+      "pretext": "Build bla bla succeeded",
+      "mrkdwn_in": [
+        "pretext"
+      ],
+      "fallback": "Build ConsumerAddressModule_20150407.2 succeeded"
+    }
+  ]
+}

zerver/webhooks/slack_incoming/fixtures/attachment_pieces.json

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+{
+  "attachments": [
+    {
+      "title": "Test",
+      "image_url": "https://pbs.twimg.com/profile_images/625633822235693056/lNGUneLX_400x400.jpg",
+      "ts": 1655945306
+    }
+  ]
+}

zerver/webhooks/slack_incoming/fixtures/attachment_pieces_all_null.json

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+{
+    "attachments": [
+        {
+            "title": null,
+            "title_link": null,
+            "image_url": null,
+            "ts": null,
+            "text": null,
+            "pretext": null,
+            "footer": null
+        }
+    ]
+}

zerver/webhooks/slack_incoming/fixtures/attachment_pieces_footer_null.json

@@ -0,0 +1,13 @@
+{
+    "attachments": [
+        {
+            "title": "Sample title.",
+            "title_link": "https://www.google.com",
+            "image_url": "https://pbs.twimg.com/profile_images/625633822235693056/lNGUneLX_400x400.jpg",
+            "ts": 1655945306,
+            "text": "Sample text.",
+            "pretext": "Sample pretext.",
+            "footer": null
+        }
+    ]
+}

zerver/webhooks/slack_incoming/fixtures/attachment_pieces_image_url_null.json

@@ -0,0 +1,13 @@
+{
+    "attachments": [
+        {
+            "title": "Sample title.",
+            "title_link": "https://www.google.com",
+            "image_url": null,
+            "ts": 1655945306,
+            "text": "Sample text.",
+            "pretext": "Sample pretext.",
+            "footer": "Sample footer."
+        }
+    ]
+}

zerver/webhooks/slack_incoming/fixtures/attachment_pieces_pretext_null.json

@@ -0,0 +1,13 @@
+{
+    "attachments": [
+        {
+            "title": "Sample title.",
+            "title_link": "https://www.google.com",
+            "image_url": "https://pbs.twimg.com/profile_images/625633822235693056/lNGUneLX_400x400.jpg",
+            "ts": 1655945306,
+            "text": "Sample text.",
+            "pretext": null,
+            "footer": "Sample footer."
+        }
+    ]
+}

zerver/webhooks/slack_incoming/fixtures/attachment_pieces_text_null.json

@@ -0,0 +1,13 @@
+{
+    "attachments": [
+        {
+            "title": "Sample title.",
+            "title_link": "https://www.google.com",
+            "image_url": "https://pbs.twimg.com/profile_images/625633822235693056/lNGUneLX_400x400.jpg",
+            "ts": 1655945306,
+            "text": null,
+            "pretext": "Sample pretext.",
+            "footer": "Sample footer."
+        }
+    ]
+}

zerver/webhooks/slack_incoming/fixtures/attachment_pieces_title_link_null.json

@@ -0,0 +1,13 @@
+{
+    "attachments": [
+        {
+            "title": "Sample title.",
+            "title_link": null,
+            "image_url": "https://pbs.twimg.com/profile_images/625633822235693056/lNGUneLX_400x400.jpg",
+            "ts": 1655945306,
+            "text": "Sample text.",
+            "pretext": "Sample pretext.",
+            "footer": "Sample footer."
+        }
+    ]
+}

zerver/webhooks/slack_incoming/fixtures/attachment_pieces_title_null.json

@@ -0,0 +1,13 @@
+{
+    "attachments": [
+        {
+            "title": null,
+            "title_link": "https://www.google.com",
+            "image_url": "https://pbs.twimg.com/profile_images/625633822235693056/lNGUneLX_400x400.jpg",
+            "ts": 1655945306,
+            "text": "Sample text.",
+            "pretext": "Sample pretext.",
+            "footer": "Sample footer."
+        }
+    ]
+}

zerver/webhooks/slack_incoming/fixtures/attachment_pieces_ts_null.json

@@ -0,0 +1,13 @@
+{
+    "attachments": [
+        {
+            "title": "Sample title.",
+            "title_link": "https://www.google.com",
+            "image_url": "https://pbs.twimg.com/profile_images/625633822235693056/lNGUneLX_400x400.jpg",
+            "ts": null,
+            "text": "Sample text.",
+            "pretext": "Sample pretext.",
+            "footer": "Sample footer."
+        }
+    ]
+}

zerver/webhooks/slack_incoming/fixtures/blocks.json

@@ -0,0 +1,35 @@
+{
+    "text": "Danny Torrence left a 1 star review for your property.",
+    "blocks": [
+        {
+            "type": "section",
+            "text": {
+                "type": "mrkdwn",
+                "text": "Danny Torrence left the following review for your property:"
+            }
+        },
+        {
+            "type": "section",
+            "block_id": "section567",
+            "text": {
+                "type": "mrkdwn",
+                "text": "<https://example.com|Overlook Hotel> \n :star: \n Doors had too many axe holes, guest in room 237 was far too rowdy, whole place felt stuck in the 1920s."
+            },
+            "accessory": {
+                "type": "image",
+                "image_url": "https://is5-ssl.mzstatic.com/image/thumb/Purple3/v4/d3/72/5c/d3725c8f-c642-5d69-1904-aa36e4297885/source/256x256bb.jpg",
+                "alt_text": "Haunted hotel image"
+            }
+        },
+        {
+            "type": "section",
+            "block_id": "section789",
+            "fields": [
+                {
+                    "type": "mrkdwn",
+                    "text": "*Average Rating*\n1.0"
+                }
+            ]
+        }
+    ]
+}

zerver/webhooks/slack_incoming/fixtures/broken_image.json

@@ -0,0 +1,16 @@
+{
+    "blocks": [
+        {
+            "type": "section",
+            "text": {
+                "type": "mrkdwn",
+                "text": "Some image here"
+            },
+            "accessory": {
+                "type": "image",
+                "alt_text": "yay",
+                "image_url": "null"
+            }
+        }
+    ]
+}

zerver/webhooks/slack_incoming/fixtures/complicated.json

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+{
+  "blocks": [
+    {
+      "type": "header",
+      "text": {
+        "type": "plain_text",
+        "text": "Hello from TaskBot",
+        "emoji": true
+      }
+    },
+    {
+      "type": "section",
+      "text": {
+        "type": "mrkdwn",
+        "text": "Hey there 👋 I'm TaskBot. I'm here to help you create and manage tasks in Slack.\nThere are two ways to quickly create tasks:"
+      }
+    },
+    {
+      "type": "section",
+      "text": {
+        "type": "mrkdwn",
+        "text": "*1️⃣ Use the `/task` command*. Type `/task` followed by a short description of your tasks and I'll ask for a due date (if applicable). Try it out by using the `/task` command in this channel."
+      }
+    },
+    {
+      "type": "section",
+      "text": {
+        "type": "mrkdwn",
+        "text": "*2️⃣ Use the _Create a Task_ action.* If you want to create a task from a message, select `Create a Task` in a message's context menu. Try it out by selecting the _Create a Task_ action for this message (shown below)."
+      }
+    },
+    {
+      "type": "image",
+      "title": {
+        "type": "plain_text",
+        "text": "image1",
+        "emoji": true
+      },
+      "image_url": "https://api.slack.com/img/blocks/bkb_template_images/onboardingComplex.jpg",
+      "alt_text": "image1"
+    },
+    {
+      "type": "section",
+      "text": {
+        "type": "mrkdwn",
+        "text": "➕ To start tracking your team's tasks, *add me to a channel* and I'll introduce myself. I'm usually added to a team or project channel. Type `/invite @TaskBot` from the channel or pick a channel on the right."
+      },
+      "accessory": {
+        "type": "conversations_select",
+        "placeholder": {
+          "type": "plain_text",
+          "text": "Select a channel...",
+          "emoji": true
+        }
+      }
+    },
+    {
+      "type": "input",
+      "element": {
+        "type": "plain_text_input",
+        "action_id": "plain_text_input-action"
+      },
+      "label": {
+        "type": "plain_text",
+        "text": "Try writing some task in here:",
+        "emoji": true
+      }
+    },
+    {
+      "type": "divider"
+    },
+    {
+      "type": "context",
+      "elements": [
+        {
+          "type": "image",
+          "image_url": "https://pbs.twimg.com/profile_images/625633822235693056/lNGUneLX_400x400.jpg",
+          "alt_text": "cute cat"
+        },
+        {
+          "type": "mrkdwn",
+          "text": "👀 View all tasks with `/task list`"
+        },
+        {
+          "type": "mrkdwn",
+            "text": "❓Get help at any time with:\n- `/task help`, or\n- type *help* in a DM with me"
+        }
+      ]
+    }
+  ]
+}

zerver/webhooks/slack_incoming/fixtures/null_text.json

@@ -0,0 +1,3 @@
+{
+    "text": null
+}

zerver/webhooks/slack_incoming/fixtures/text.json

@@ -0,0 +1,3 @@
+{
+    "text": "Hello, world."
+}

zerver/webhooks/slack_incoming/fixtures/urlencoded_text.txt

@@ -0,0 +1 @@
+payload=%7B%22username%22%3A%22DeployBot%22%2C%22icon_url%22%3A%22https%3A%2F%2Fraw.githubusercontent.com%2Fphallstrom%2Fslackistrano%2Fmaster%2Fimages%2Fslackistrano.png%22%2C%22icon_emoji%22%3A%22%3Azap%3A%22%2C%22text%22%3A%22chris+has+started+deploying+project+tag+v0.0.2rc10+to+staging%22%2C%22channel%22%3A%22%23devops%22%7D

zerver/webhooks/slack_incoming/tests.py

@@ -0,0 +1,387 @@
+from typing_extensions import override
+
+from zerver.lib.test_classes import WebhookTestCase
+
+
+class SlackIncomingHookTests(WebhookTestCase):
+    def test_message(self) -> None:
+        expected_topic_name = ""
+        expected_message = """
+Hello, world.
+""".strip()
+
+        self.check_webhook(
+            "text",
+            expected_topic_name,
+            expected_message,
+        )
+
+    def test_message_formatting(self) -> None:
+        tests = [
+            ("some *foo* word", "some **foo** word"),
+            ("*foo*", "**foo**"),
+            ("*foo* *bar*", "**foo** **bar**"),
+            ("*foo*a*bar*", "*foo*a*bar*"),
+            ("some _foo_ word", "some *foo* word"),
+        ]
+        self.subscribe(self.test_user, self.channel_name)
+        for input_value, output_value in tests:
+            payload = {"text": input_value}
+            msg = self.send_webhook_payload(
+                self.test_user,
+                self.url,
+                payload,
+                content_type="application/json",
+            )
+            self.assert_channel_message(
+                message=msg,
+                channel_name=self.channel_name,
+                topic_name="",
+                content=output_value,
+            )
+
+    def test_null_message(self) -> None:
+        self.check_webhook(
+            "null_text",
+            expect_noop=True,
+        )
+
+    def test_message_as_www_urlencoded(self) -> None:
+        expected_topic_name = "devops"
+        expected_message = """
+:zap: chris has started deploying project tag v0.0.2rc10 to staging
+""".strip()
+
+        self.check_webhook(
+            "urlencoded_text",
+            expected_topic_name,
+            expected_message,
+            content_type="application/x-www-form-urlencoded",
+        )
+
+    def test_message_without_payload(self) -> None:
+        self.url = self.build_webhook_url()
+        result = self.client_post(self.url)
+        self.assertEqual(result.json()["error"], "Missing 'payload' argument")
+        self.assertEqual(result.json()["ok"], False)
+
+    def test_message_with_actions(self) -> None:
+        expected_topic_name = "C1H9RESGL"
+        expected_message = """
+Danny Torrence left the following *review* for your property:
+
+[Overlook Hotel](https://google.com) \n :star: \n Doors had too many axe holes, guest in room 237 was far too rowdy, whole place felt stuck in the 1920s.
+
+[Haunted hotel image](https://is5-ssl.mzstatic.com/image/thumb/Purple3/v4/d3/72/5c/d3725c8f-c642-5d69-1904-aa36e4297885/source/256x256bb.jpg)
+
+**Average Rating**
+1.0
+""".strip()
+
+        self.check_webhook(
+            "actions",
+            expected_topic_name,
+            expected_message,
+        )
+
+    def test_message_with_blocks(self) -> None:
+        expected_topic_name = ""
+        expected_message = """
+Danny Torrence left the following review for your property:
+
+[Overlook Hotel](https://example.com) \n :star: \n Doors had too many axe holes, guest in room 237 was far too rowdy, whole place felt stuck in the 1920s.
+
+[Haunted hotel image](https://is5-ssl.mzstatic.com/image/thumb/Purple3/v4/d3/72/5c/d3725c8f-c642-5d69-1904-aa36e4297885/source/256x256bb.jpg)
+
+**Average Rating**
+1.0
+""".strip()
+
+        self.check_webhook(
+            "blocks",
+            expected_topic_name,
+            expected_message,
+        )
+
+    def test_message_with_attachment(self) -> None:
+        expected_topic_name = "prometheus-alerts"
+        expected_message = """
+## [[FIRING:2] InstanceDown for api-server (env="prod", severity="critical")](https://alertmanager.local//#/alerts?receiver=default)
+
+:chart_with_upwards_trend: **[Graph](http://generator.local/1)**   :notebook: **[Runbook](https://runbook.local/1)**
+
+**Alert details**:
+**Alert:** api-server down - `critical`
+**Description:** api-server at 1.2.3.4:8080 couldn't be scraped **Details:**
+   • **alertname:** `InstanceDown`
+   • **env:** `prod`
+   • **instance:** `1.2.3.4:8080`
+   • **job:** `api-server`
+   • **severity:** `critical`
+
+**Alert:** api-server down - `critical`
+**Description:** api-server at 1.2.3.4:8081 couldn't be scraped **Details:**
+   • **alertname:** `InstanceDown`
+   • **env:** `prod`
+   • **instance:** `1.2.3.4:8081`
+   • **job:** `api-server`
+   • **severity:** `critical`
+""".strip()
+
+        self.check_webhook(
+            "attachment",
+            expected_topic_name,
+            expected_message,
+        )
+
+    def test_complicated(self) -> None:
+        # Paste the JSON into
+        # https://api.slack.com/tools/block-kit-builder to see how it
+        # is rendered in Slack
+        expected_topic_name = ""
+        expected_message = """
+## Hello from TaskBot
+
+Hey there 👋 I'm TaskBot. I'm here to help you create and manage tasks in Slack.
+There are two ways to quickly create tasks:
+
+**1️⃣ Use the `/task` command**. Type `/task` followed by a short description of your tasks and I'll ask for a due date (if applicable). Try it out by using the `/task` command in this channel.
+
+**2️⃣ Use the *Create a Task* action.** If you want to create a task from a message, select `Create a Task` in a message's context menu. Try it out by selecting the *Create a Task* action for this message (shown below).
+
+[image1](https://api.slack.com/img/blocks/bkb_template_images/onboardingComplex.jpg)
+
+➕ To start tracking your team's tasks, **add me to a channel** and I'll introduce myself. I'm usually added to a team or project channel. Type `/invite @TaskBot` from the channel or pick a channel on the right.
+
+----
+
+[cute cat](https://pbs.twimg.com/profile_images/625633822235693056/lNGUneLX_400x400.jpg)
+
+👀 View all tasks with `/task list`
+
+❓Get help at any time with:
+- `/task help`, or
+- type **help** in a DM with me
+        """.strip()
+
+        self.check_webhook(
+            "complicated",
+            expected_topic_name,
+            expected_message,
+        )
+
+    def test_attachment_blocks(self) -> None:
+        # On https://api.slack.com/tools/block-kit-builder choose
+        # "Attachment preview" and paste the JSON in.
+        expected_topic_name = ""
+        expected_message = """
+This is a section block with an accessory image.
+
+[cute cat](https://pbs.twimg.com/profile_images/625633822235693056/lNGUneLX_400x400.jpg)
+
+This is a section block with a button.
+
+| | |
+|-|-|
+| one | two |
+| three | four |
+| five |  |
+        """.strip()
+
+        self.check_webhook(
+            "attachment_blocks",
+            expected_topic_name,
+            expected_message,
+        )
+
+    def test_attachment_fields(self) -> None:
+        expected_topic_name = ""
+        expected_message = """
+Build bla bla succeeded
+
+**Requested by**: Some user
+**Duration**: 00:02:03
+**Build pipeline**: ConsumerAddressModule
+**Title with null value**
+**Title without value**
+Value with null title
+Value without title
+        """.strip()
+
+        self.check_webhook(
+            "attachment_fields",
+            expected_topic_name,
+            expected_message,
+        )
+
+    def test_attachment_pieces(self) -> None:
+        expected_topic_name = ""
+        expected_message = """
+## Test
+
+[](https://pbs.twimg.com/profile_images/625633822235693056/lNGUneLX_400x400.jpg)
+
+<time:2022-06-23T00:48:26+00:00>
+        """.strip()
+
+        self.check_webhook(
+            "attachment_pieces",
+            expected_topic_name,
+            expected_message,
+        )
+
+    @override
+    def get_body(self, fixture_name: str) -> str:
+        if "urlencoded" in fixture_name:
+            file_type = "txt"
+        else:
+            file_type = "json"
+        return self.webhook_fixture_data("slack_incoming", fixture_name, file_type=file_type)
+
+    def test_attachment_pieces_title_null(self) -> None:
+        expected_topic_name = ""
+        expected_message = """
+Sample pretext.
+
+Sample text.
+
+[](https://pbs.twimg.com/profile_images/625633822235693056/lNGUneLX_400x400.jpg)
+
+Sample footer.
+
+<time:2022-06-23T00:48:26+00:00>
+        """.strip()
+
+        self.check_webhook(
+            "attachment_pieces_title_null",
+            expected_topic_name,
+            expected_message,
+        )
+
+    def test_attachment_pieces_image_url_null(self) -> None:
+        expected_topic_name = ""
+        expected_message = """
+## [Sample title.](https://www.google.com)
+
+Sample pretext.
+
+Sample text.
+
+Sample footer.
+
+<time:2022-06-23T00:48:26+00:00>
+        """.strip()
+
+        self.check_webhook(
+            "attachment_pieces_image_url_null",
+            expected_topic_name,
+            expected_message,
+        )
+
+    def test_attachment_pieces_ts_null(self) -> None:
+        expected_topic_name = ""
+        expected_message = """
+## [Sample title.](https://www.google.com)
+
+Sample pretext.
+
+Sample text.
+
+[](https://pbs.twimg.com/profile_images/625633822235693056/lNGUneLX_400x400.jpg)
+
+Sample footer.
+        """.strip()
+
+        self.check_webhook(
+            "attachment_pieces_ts_null",
+            expected_topic_name,
+            expected_message,
+        )
+
+    def test_attachment_pieces_text_null(self) -> None:
+        expected_topic_name = ""
+        expected_message = """
+## [Sample title.](https://www.google.com)
+
+Sample pretext.
+
+[](https://pbs.twimg.com/profile_images/625633822235693056/lNGUneLX_400x400.jpg)
+
+Sample footer.
+
+<time:2022-06-23T00:48:26+00:00>
+        """.strip()
+
+        self.check_webhook(
+            "attachment_pieces_text_null",
+            expected_topic_name,
+            expected_message,
+        )
+
+    def test_attachment_pieces_pretext_null(self) -> None:
+        expected_topic_name = ""
+        expected_message = """
+## [Sample title.](https://www.google.com)
+
+Sample text.
+
+[](https://pbs.twimg.com/profile_images/625633822235693056/lNGUneLX_400x400.jpg)
+
+Sample footer.
+
+<time:2022-06-23T00:48:26+00:00>
+        """.strip()
+
+        self.check_webhook(
+            "attachment_pieces_pretext_null",
+            expected_topic_name,
+            expected_message,
+        )
+
+    def test_attachment_pieces_footer_null(self) -> None:
+        expected_topic_name = ""
+        expected_message = """
+## [Sample title.](https://www.google.com)
+
+Sample pretext.
+
+Sample text.
+
+[](https://pbs.twimg.com/profile_images/625633822235693056/lNGUneLX_400x400.jpg)
+
+<time:2022-06-23T00:48:26+00:00>
+        """.strip()
+
+        self.check_webhook(
+            "attachment_pieces_footer_null",
+            expected_topic_name,
+            expected_message,
+        )
+
+    def test_attachment_pieces_title_link_null(self) -> None:
+        expected_topic_name = ""
+        expected_message = """
+## Sample title.
+
+Sample pretext.
+
+Sample text.
+
+[](https://pbs.twimg.com/profile_images/625633822235693056/lNGUneLX_400x400.jpg)
+
+Sample footer.
+
+<time:2022-06-23T00:48:26+00:00>
+        """.strip()
+
+        self.check_webhook(
+            "attachment_pieces_title_link_null",
+            expected_topic_name,
+            expected_message,
+        )
+
+    def test_attachment_pieces_all_null(self) -> None:
+        self.check_webhook("attachment_pieces_all_null", expect_noop=True)
+
+    def test_broken_image(self) -> None:
+        self.check_webhook("broken_image", "", "Some image here")

zerver/webhooks/slack_incoming/view.py

@@ -0,0 +1,107 @@
+# Webhooks for external integrations.
+import re
+from collections.abc import Callable
+from functools import wraps
+from typing import Concatenate
+
+from django.http import HttpRequest, HttpResponse, JsonResponse
+from django.utils.translation import gettext as _
+from typing_extensions import ParamSpec
+
+from zerver.data_import.slack_message_conversion import (
+    LossyConversionError,
+    convert_slack_formatting,
+    render_attachment,
+    render_block,
+    replace_links,
+)
+from zerver.decorator import webhook_view
+from zerver.lib.exceptions import JsonableError
+from zerver.lib.request import RequestVariableMissingError
+from zerver.lib.response import json_success
+from zerver.lib.typed_endpoint import typed_endpoint
+from zerver.lib.validator import check_string, to_wild_value
+from zerver.lib.webhooks.common import OptionalUserSpecifiedTopicStr, check_send_webhook_message
+from zerver.models import UserProfile
+
+ParamT = ParamSpec("ParamT")
+
+
+def slack_error_handler(
+    view_func: Callable[Concatenate[HttpRequest, ParamT], HttpResponse],
+) -> Callable[Concatenate[HttpRequest, ParamT], HttpResponse]:
+    """
+    A decorator that catches JsonableError exceptions and returns a
+    Slack-compatible error response in the format:
+    {ok: false, error: "error message"}.
+    """
+
+    @wraps(view_func)
+    def wrapped_view(
+        request: HttpRequest, /, *args: ParamT.args, **kwargs: ParamT.kwargs
+    ) -> HttpResponse:
+        try:
+            return view_func(request, *args, **kwargs)
+        except JsonableError as error:
+            return JsonResponse({"ok": False, "error": error.msg}, status=error.http_status_code)
+
+    return wrapped_view
+
+
+@webhook_view("SlackIncoming")
+@typed_endpoint
+@slack_error_handler
+def api_slack_incoming_webhook(
+    request: HttpRequest,
+    user_profile: UserProfile,
+    *,
+    user_specified_topic: OptionalUserSpecifiedTopicStr = None,
+) -> HttpResponse:
+    # Slack accepts webhook payloads as payload="encoded json" as
+    # application/x-www-form-urlencoded, as well as in the body as
+    # application/json.
+    if request.content_type == "application/json":
+        try:
+            val = request.body.decode(request.encoding or "utf-8")
+        except UnicodeDecodeError:  # nocoverage
+            raise JsonableError(_("Malformed payload"))
+    else:
+        req_var = "payload"
+        if req_var in request.POST:
+            val = request.POST[req_var]
+        elif req_var in request.GET:  # nocoverage
+            val = request.GET[req_var]
+        else:
+            raise RequestVariableMissingError(req_var)
+
+    payload = to_wild_value("payload", val)
+
+    if user_specified_topic is None and "channel" in payload:
+        channel = payload["channel"].tame(check_string)
+        user_specified_topic = re.sub(r"^[@#]", "", channel)
+
+    if user_specified_topic is None:
+        user_specified_topic = "(no topic)"
+
+    pieces: list[str] = []
+    if payload.get("blocks"):
+        try:
+            pieces += map(render_block, payload["blocks"])
+        except LossyConversionError:  # nocoverage
+            pieces.append(payload.get("text", "").tame(check_string))
+
+    if payload.get("attachments"):
+        pieces += map(render_attachment, payload["attachments"])
+
+    body = "\n\n".join(piece.strip() for piece in pieces if piece.strip() != "")
+
+    if body == "" and payload.get("text"):
+        if payload.get("icon_emoji"):
+            body = payload["icon_emoji"].tame(check_string) + " "
+        body += payload["text"].tame(check_string)
+        body = body.strip()
+
+    if body != "":
+        body = convert_slack_formatting(replace_links(body).strip())
+        check_send_webhook_message(request, user_profile, user_specified_topic, body)
+    return json_success(request, data={"ok": True})