Add create-file-tool (#27381)

<img width="627" alt="Screenshot 2025-03-24 at 12 52 04 PM"
src="https://github.com/user-attachments/assets/0e8c061a-11c5-4d60-a694-55575b6c8f5e"
/>

Release Notes:

- N/A

crates/assistant_tools/src/create_file_tool.rs

@@ -0,0 +1,106 @@
+use anyhow::{anyhow, Result};
+use assistant_tool::{ActionLog, Tool};
+use gpui::{App, Entity, Task};
+use language_model::LanguageModelRequestMessage;
+use project::Project;
+use schemars::JsonSchema;
+use serde::{Deserialize, Serialize};
+use std::sync::Arc;
+
+#[derive(Debug, Serialize, Deserialize, JsonSchema)]
+pub struct CreateFileToolInput {
+    /// The path where the file should be created.
+    ///
+    /// <example>
+    /// If the project has the following structure:
+    ///
+    /// - directory1/
+    /// - directory2/
+    ///
+    /// You can create a new file by providing a path of "directory1/new_file.txt"
+    /// </example>
+    pub path: String,
+
+    /// The text contents of the file to create.
+    ///
+    /// <example>
+    /// To create a file with the text "Hello, World!", provide contents of "Hello, World!"
+    /// </example>
+    pub contents: String,
+}
+
+pub struct CreateFileTool;
+
+impl Tool for CreateFileTool {
+    fn name(&self) -> String {
+        "create-file".into()
+    }
+
+    fn needs_confirmation(&self) -> bool {
+        true
+    }
+
+    fn description(&self) -> String {
+        include_str!("./create_file_tool/description.md").into()
+    }
+
+    fn input_schema(&self) -> serde_json::Value {
+        let schema = schemars::schema_for!(CreateFileToolInput);
+        serde_json::to_value(&schema).unwrap()
+    }
+
+    fn ui_text(&self, input: &serde_json::Value) -> String {
+        match serde_json::from_value::<CreateFileToolInput>(input.clone()) {
+            Ok(input) => {
+                let path = input.path.as_str();
+                format!("Create file `{path}`")
+            }
+            Err(_) => "Create file".to_string(),
+        }
+    }
+
+    fn run(
+        self: Arc<Self>,
+        input: serde_json::Value,
+        _messages: &[LanguageModelRequestMessage],
+        project: Entity<Project>,
+        _action_log: Entity<ActionLog>,
+        cx: &mut App,
+    ) -> Task<Result<String>> {
+        let input = match serde_json::from_value::<CreateFileToolInput>(input) {
+            Ok(input) => input,
+            Err(err) => return Task::ready(Err(anyhow!(err))),
+        };
+        let project_path = match project.read(cx).find_project_path(&input.path, cx) {
+            Some(project_path) => project_path,
+            None => return Task::ready(Err(anyhow!("Path to create was outside the project"))),
+        };
+        let contents: Arc<str> = input.contents.as_str().into();
+        let destination_path: Arc<str> = input.path.as_str().into();
+
+        cx.spawn(async move |cx| {
+            project
+                .update(cx, |project, cx| {
+                    project.create_entry(project_path.clone(), false, cx)
+                })?
+                .await
+                .map_err(|err| anyhow!("Unable to create {destination_path}: {err}"))?;
+            let buffer = project
+                .update(cx, |project, cx| {
+                    project.open_buffer(project_path.clone(), cx)
+                })?
+                .await
+                .map_err(|err| anyhow!("Unable to open buffer for {destination_path}: {err}"))?;
+            buffer.update(cx, |buffer, cx| {
+                buffer.set_text(contents, cx);
+            })?;
+
+            project
+                .update(cx, |project, cx| project.save_buffer(buffer.clone(), cx))?
+                .await
+                .map_err(|err| anyhow!("Unable to save buffer for {destination_path}: {err}"))?;
+
+            Ok(format!("Created file {destination_path}"))
+        })
+    }
+}