extension_host: Load granted extension capabilities from settings (#39472)

This PR adds the ability to control the capabilities granted to
extensions by the extension host via the new
`granted_extension_capabilities` setting.

This setting is a list of the capabilities granted to any extension
running in Zed.

The currently available capabilities are:

- `process:exec` - Grants extensions the ability to invoke commands
using
[`zed_extension_api::process::Command`](https://docs.rs/zed_extension_api/latest/zed_extension_api/process/struct.Command.html)
- `download_file` - Grants extensions the ability to download files
using
[`zed_extension_api::download_file`](https://docs.rs/zed_extension_api/latest/zed_extension_api/fn.download_file.html)
- `npm:install` - Grants extensions the ability to install npm packages
using
[`zed_extension_api::npm_install_package`](https://docs.rs/zed_extension_api/latest/zed_extension_api/fn.npm_install_package.html)

Each of these capabilities has parameters that can be used to customize
the permissions.

For instance, to only allow downloads from GitHub, the `download_file`
capability can specify an allowed `host`:

```json
[
  { "kind": "download_file", "host": "github.com", "path": ["**"] }
]
```

The same capability can also be granted multiple times with different
parameters to build up an allowlist:

```json
[
  { "kind": "download_file", "host": "github.com", "path": ["**"] },
  { "kind": "download_file", "host": "gitlab.com", "path": ["**"] }
]
```

When an extension is not granted a capability, the associated extension
APIs protected by that capability will fail.

For instance, trying to use `zed_extension_api::download_file` when the
`download_file` capability is not granted will result in an error that
will be surfaced by the extension:

```
Language server phpactor:

from extension "PHP" version 0.4.3: failed to download file: capability for download_file https://github.com/phpactor/phpactor/releases/download/2025.07.25.0/phpactor.phar is not granted by the extension host
```

Release Notes:

- Added a `granted_extension_capabilities` setting to control the
capabilities granted to extensions.

crates/extension_host/src/extension_settings.rs

@@ -1,4 +1,7 @@
 use collections::HashMap;
+use extension::{
+    DownloadFileCapability, ExtensionCapability, NpmInstallPackageCapability, ProcessExecCapability,
+};
 use gpui::App;
 use settings::Settings;
 use std::sync::Arc;
@@ -13,6 +16,7 @@ pub struct ExtensionSettings {
     /// Default: { "html": true }
     pub auto_install_extensions: HashMap<Arc<str>, bool>,
     pub auto_update_extensions: HashMap<Arc<str>, bool>,
+    pub granted_capabilities: Vec<ExtensionCapability>,
 }
 
 impl ExtensionSettings {
@@ -37,6 +41,32 @@ impl Settings for ExtensionSettings {
         Self {
             auto_install_extensions: content.extension.auto_install_extensions.clone(),
             auto_update_extensions: content.extension.auto_update_extensions.clone(),
+            granted_capabilities: content
+                .extension
+                .granted_extension_capabilities
+                .clone()
+                .unwrap_or_default()
+                .into_iter()
+                .map(|capability| match capability {
+                    settings::ExtensionCapabilityContent::ProcessExec(capability) => {
+                        ExtensionCapability::ProcessExec(ProcessExecCapability {
+                            command: capability.command,
+                            args: capability.args,
+                        })
+                    }
+                    settings::ExtensionCapabilityContent::DownloadFile(capability) => {
+                        ExtensionCapability::DownloadFile(DownloadFileCapability {
+                            host: capability.host,
+                            path: capability.path,
+                        })
+                    }
+                    settings::ExtensionCapabilityContent::NpmInstallPackage(capability) => {
+                        ExtensionCapability::NpmInstallPackage(NpmInstallPackageCapability {
+                            package: capability.package,
+                        })
+                    }
+                })
+                .collect(),
         }
     }
 }

crates/extension_host/src/wasm_host.rs

@@ -1,15 +1,15 @@
 pub mod wit;
 
-use crate::ExtensionManifest;
 use crate::capability_granter::CapabilityGranter;
+use crate::{ExtensionManifest, ExtensionSettings};
 use anyhow::{Context as _, Result, anyhow, bail};
 use async_trait::async_trait;
 use dap::{DebugRequest, StartDebuggingRequestArgumentsRequest};
 use extension::{
     CodeLabel, Command, Completion, ContextServerConfiguration, DebugAdapterBinary,
-    DebugTaskDefinition, DownloadFileCapability, ExtensionCapability, ExtensionHostProxy,
-    KeyValueStoreDelegate, NpmInstallPackageCapability, ProcessExecCapability, ProjectDelegate,
-    SlashCommand, SlashCommandArgumentCompletion, SlashCommandOutput, Symbol, WorktreeDelegate,
+    DebugTaskDefinition, ExtensionCapability, ExtensionHostProxy, KeyValueStoreDelegate,
+    ProjectDelegate, SlashCommand, SlashCommandArgumentCompletion, SlashCommandOutput, Symbol,
+    WorktreeDelegate,
 };
 use fs::{Fs, normalize_path};
 use futures::future::LocalBoxFuture;
@@ -29,6 +29,7 @@ use moka::sync::Cache;
 use node_runtime::NodeRuntime;
 use release_channel::ReleaseChannel;
 use semantic_version::SemanticVersion;
+use settings::Settings;
 use std::borrow::Cow;
 use std::sync::{LazyLock, OnceLock};
 use std::time::Duration;
@@ -569,6 +570,9 @@ impl WasmHost {
                 message(cx).await;
             }
         });
+
+        let extension_settings = ExtensionSettings::get_global(cx);
+
         Arc::new(Self {
             engine: wasm_engine(cx.background_executor()),
             fs,
@@ -577,19 +581,7 @@ impl WasmHost {
             node_runtime,
             proxy,
             release_channel: ReleaseChannel::global(cx),
-            granted_capabilities: vec![
-                ExtensionCapability::ProcessExec(ProcessExecCapability {
-                    command: "*".to_string(),
-                    args: vec!["**".to_string()],
-                }),
-                ExtensionCapability::DownloadFile(DownloadFileCapability {
-                    host: "*".to_string(),
-                    path: vec!["**".to_string()],
-                }),
-                ExtensionCapability::NpmInstallPackage(NpmInstallPackageCapability {
-                    package: "*".to_string(),
-                }),
-            ],
+            granted_capabilities: extension_settings.granted_capabilities.clone(),
             _main_thread_message_task: task,
             main_thread_message_tx: tx,
         })