feat: add --upload-content-type flag and smart MIME inference for uploads (#429)

The multipart upload media Content-Type is now resolved independently
from the metadata mimeType, enabling Drive import conversions (e.g.
Markdown → Google Docs) to work automatically.

Priority order for the media MIME type:
1. --upload-content-type flag (explicit override)
2. File extension inference (best guess for what the bytes are)
3. Metadata mimeType (backward-compat fallback)
4. application/octet-stream

Previously the metadata mimeType was reused for the media part, which
meant uploading `notes.md` with mimeType set to
`application/vnd.google-apps.document` would incorrectly label the
bytes as a Google Doc instead of text/markdown.

Made-with: Cursor

.changeset/upload-content-type.md

@@ -0,0 +1,30 @@
+---
+"@googleworkspace/cli": minor
+---
+
+Add `--upload-content-type` flag and smart MIME inference for multipart uploads
+
+Previously, multipart uploads used the metadata `mimeType` field for both the Drive
+metadata and the media part's `Content-Type` header. This made it impossible to upload
+a file in one format (e.g. Markdown) and have Drive convert it to another (e.g. Google Docs),
+because the media `Content-Type` and the target `mimeType` must differ for import conversions.
+
+The new `--upload-content-type` flag allows setting the media `Content-Type` explicitly.
+When omitted, the media type is now inferred from the file extension before falling back
+to the metadata `mimeType`. This matches Google Drive's model where metadata `mimeType`
+is the *target* type (what the file should become) while the media `Content-Type` is the
+*source* type (what the bytes are).
+
+This means import conversions now work automatically:
+```bash
+# Extension inference detects text/markdown → conversion just works
+gws drive files create \
+  --json '{"name":"My Doc","mimeType":"application/vnd.google-apps.document"}' \
+  --upload notes.md
+
+# Explicit flag still available as an override
+gws drive files create \
+  --json '{"name":"My Doc","mimeType":"application/vnd.google-apps.document"}' \
+  --upload notes.md \
+  --upload-content-type text/markdown
+```

src/commands.rs

@@ -122,12 +122,19 @@ fn build_resource_command(name: &str, resource: &RestResource) -> Option<Command
 
         // Add --upload flag if the method supports media upload
         if method.supports_media_upload {
-            method_cmd = method_cmd.arg(
-                Arg::new("upload")
-                    .long("upload")
-                    .help("Local file path to upload as media content (multipart upload)")
-                    .value_name("PATH"),
-            );
+            method_cmd = method_cmd
+                .arg(
+                    Arg::new("upload")
+                        .long("upload")
+                        .help("Local file path to upload as media content (multipart upload)")
+                        .value_name("PATH"),
+                )
+                .arg(
+                    Arg::new("upload-content-type")
+                        .long("upload-content-type")
+                        .help("MIME type of the uploaded file content (e.g. text/markdown). If omitted, detected from file extension or metadata mimeType")
+                        .value_name("MIME"),
+                );
         }
 
         // Pagination flags

src/executor.rs

@@ -145,6 +145,7 @@ async fn build_http_request(
     page_token: Option<&str>,
     pages_fetched: u32,
     upload_path: Option<&str>,
+    upload_content_type: Option<&str>,
 ) -> Result<reqwest::RequestBuilder, GwsError> {
     let mut request = match method.http_method.as_str() {
         "GET" => client.get(&input.full_url),
@@ -190,7 +191,9 @@ async fn build_http_request(
             })?;
 
             request = request.query(&[("uploadType", "multipart")]);
-            let (multipart_body, content_type) = build_multipart_body(&input.body, &file_bytes)?;
+            let media_mime = resolve_upload_mime(upload_content_type, Some(upload_path), &input.body);
+            let (multipart_body, content_type) =
+                build_multipart_body(&input.body, &file_bytes, &media_mime)?;
             request = request.header("Content-Type", content_type);
             request = request.body(multipart_body);
         } else if let Some(ref body_val) = input.body {
@@ -367,6 +370,7 @@ pub async fn execute_method(
     auth_method: AuthMethod,
     output_path: Option<&str>,
     upload_path: Option<&str>,
+    upload_content_type: Option<&str>,
     dry_run: bool,
     pagination: &PaginationConfig,
     sanitize_template: Option<&str>,
@@ -410,6 +414,7 @@ pub async fn execute_method(
             page_token.as_deref(),
             pages_fetched,
             upload_path,
+            upload_content_type,
         )
         .await?;
 
@@ -754,22 +759,89 @@ fn handle_error_response<T>(
     })
 }
 
+/// Resolves the MIME type for the uploaded media content.
+///
+/// Priority:
+/// 1. `--upload-content-type` flag (explicit override)
+/// 2. File extension inference (best guess for what the bytes actually are)
+/// 3. Metadata `mimeType` (fallback for backward compatibility)
+/// 4. `application/octet-stream`
+///
+/// Extension inference ranks above metadata `mimeType` because in Google
+/// Drive's multipart model, metadata `mimeType` represents the *target* type
+/// (what the file should become in Drive), while the media `Content-Type`
+/// represents the *source* type (what the bytes are). When a user uploads
+/// `notes.md` with `"mimeType":"application/vnd.google-apps.document"`, the
+/// media part should be `text/markdown`, not a Google Workspace MIME type.
+fn resolve_upload_mime(
+    explicit: Option<&str>,
+    upload_path: Option<&str>,
+    metadata: &Option<Value>,
+) -> String {
+    if let Some(mime) = explicit {
+        return mime.to_string();
+    }
+
+    if let Some(path) = upload_path {
+        if let Some(detected) = mime_from_extension(path) {
+            return detected.to_string();
+        }
+    }
+
+    if let Some(mime) = metadata
+        .as_ref()
+        .and_then(|m| m.get("mimeType"))
+        .and_then(|v| v.as_str())
+    {
+        return mime.to_string();
+    }
+
+    "application/octet-stream".to_string()
+}
+
+/// Infers a MIME type from a file path's extension.
+fn mime_from_extension(path: &str) -> Option<&'static str> {
+    let ext = std::path::Path::new(path)
+        .extension()
+        .and_then(|e| e.to_str())?;
+    match ext.to_lowercase().as_str() {
+        "md" | "markdown" => Some("text/markdown"),
+        "html" | "htm" => Some("text/html"),
+        "txt" => Some("text/plain"),
+        "json" => Some("application/json"),
+        "csv" => Some("text/csv"),
+        "xml" => Some("application/xml"),
+        "pdf" => Some("application/pdf"),
+        "png" => Some("image/png"),
+        "jpg" | "jpeg" => Some("image/jpeg"),
+        "gif" => Some("image/gif"),
+        "svg" => Some("image/svg+xml"),
+        "doc" => Some("application/msword"),
+        "docx" => Some(
+            "application/vnd.openxmlformats-officedocument.wordprocessingml.document",
+        ),
+        "xls" => Some("application/vnd.ms-excel"),
+        "xlsx" => Some(
+            "application/vnd.openxmlformats-officedocument.spreadsheetml.sheet",
+        ),
+        "ppt" => Some("application/vnd.ms-powerpoint"),
+        "pptx" => Some(
+            "application/vnd.openxmlformats-officedocument.presentationml.presentation",
+        ),
+        _ => None,
+    }
+}
+
 /// Builds a multipart/related body for media upload requests.
 ///
 /// Returns the body bytes and the Content-Type header value (with boundary).
 fn build_multipart_body(
     metadata: &Option<Value>,
     file_bytes: &[u8],
+    media_mime: &str,
 ) -> Result<(Vec<u8>, String), GwsError> {
     let boundary = format!("gws_boundary_{:016x}", rand::random::<u64>());
 
-    // Determine the media MIME type from the metadata's mimeType field, or fall back
-    let media_mime = metadata
-        .as_ref()
-        .and_then(|m| m.get("mimeType"))
-        .and_then(|v| v.as_str())
-        .unwrap_or("application/octet-stream");
-
     // Build multipart/related body
     let metadata_json = metadata
         .as_ref()
@@ -1216,7 +1288,8 @@ mod tests {
         let metadata = Some(json!({ "name": "test.txt", "mimeType": "text/plain" }));
         let content = b"Hello world";
 
-        let (body, content_type) = build_multipart_body(&metadata, content).unwrap();
+        let (body, content_type) =
+            build_multipart_body(&metadata, content, "text/plain").unwrap();
 
         // Check content type has boundary
         assert!(content_type.starts_with("multipart/related; boundary="));
@@ -1237,15 +1310,72 @@ mod tests {
         let metadata = None;
         let content = b"Binary data";
 
-        let (body, content_type) = build_multipart_body(&metadata, content).unwrap();
+        let (body, content_type) =
+            build_multipart_body(&metadata, content, "application/octet-stream").unwrap();
         let boundary = content_type.split("boundary=").nth(1).unwrap();
         let body_str = String::from_utf8(body).unwrap();
 
         assert!(body_str.contains(boundary));
-        assert!(body_str.contains("application/octet-stream")); // Fallback mime
+        assert!(body_str.contains("application/octet-stream"));
         assert!(body_str.contains("Binary data"));
     }
 
+    #[test]
+    fn test_resolve_upload_mime_explicit_flag() {
+        let metadata = Some(json!({ "mimeType": "image/png" }));
+        let mime = resolve_upload_mime(Some("text/markdown"), Some("file.txt"), &metadata);
+        assert_eq!(mime, "text/markdown", "explicit flag takes top priority");
+    }
+
+    #[test]
+    fn test_resolve_upload_mime_extension_beats_metadata() {
+        let metadata = Some(json!({ "mimeType": "application/vnd.google-apps.document" }));
+        let mime = resolve_upload_mime(None, Some("notes.md"), &metadata);
+        assert_eq!(
+            mime, "text/markdown",
+            "extension inference ranks above metadata mimeType"
+        );
+    }
+
+    #[test]
+    fn test_resolve_upload_mime_metadata_fallback_for_unknown_extension() {
+        let metadata = Some(json!({ "mimeType": "text/plain" }));
+        let mime = resolve_upload_mime(None, Some("file.unknown"), &metadata);
+        assert_eq!(
+            mime, "text/plain",
+            "metadata mimeType is used when extension is unrecognized"
+        );
+    }
+
+    #[test]
+    fn test_resolve_upload_mime_extension_when_no_metadata() {
+        let mime = resolve_upload_mime(None, Some("notes.md"), &None);
+        assert_eq!(mime, "text/markdown");
+
+        let mime = resolve_upload_mime(None, Some("page.html"), &None);
+        assert_eq!(mime, "text/html");
+
+        let mime = resolve_upload_mime(None, Some("data.csv"), &None);
+        assert_eq!(mime, "text/csv");
+    }
+
+    #[test]
+    fn test_resolve_upload_mime_fallback() {
+        let mime = resolve_upload_mime(None, Some("file.unknown"), &None);
+        assert_eq!(mime, "application/octet-stream");
+    }
+
+    #[test]
+    fn test_resolve_upload_mime_explicit_enables_import_conversion() {
+        let metadata = Some(json!({ "mimeType": "application/vnd.google-apps.document" }));
+        let mime =
+            resolve_upload_mime(Some("text/markdown"), Some("impact.md"), &metadata);
+        assert_eq!(
+            mime, "text/markdown",
+            "--upload-content-type overrides metadata for media part"
+        );
+    }
+
     #[test]
     fn test_build_url_basic() {
         let doc = RestDescription {
@@ -1735,6 +1865,7 @@ async fn test_execute_method_dry_run() {
         AuthMethod::None,
         None,
         None,
+        None,
         true, // dry_run
         &pagination,
         None,
@@ -1778,6 +1909,7 @@ async fn test_execute_method_missing_path_param() {
         AuthMethod::None,
         None,
         None,
+        None,
         true,
         &PaginationConfig::default(),
         None,
@@ -1955,6 +2087,7 @@ async fn test_post_without_body_sets_content_length_zero() {
         None,
         0,
         None,
+        None,
     )
     .await
     .unwrap();
@@ -1995,6 +2128,7 @@ async fn test_post_with_body_does_not_add_content_length_zero() {
         None,
         0,
         None,
+        None,
     )
     .await
     .unwrap();
@@ -2033,6 +2167,7 @@ async fn test_get_does_not_set_content_length_zero() {
         None,
         0,
         None,
+        None,
     )
     .await
     .unwrap();

src/helpers/calendar.rs

@@ -170,6 +170,7 @@ TIPS:
                     auth_method,
                     None,
                     None,
+                    None,
                     matches.get_flag("dry-run"),
                     &executor::PaginationConfig::default(),
                     None,

src/helpers/chat.rs

@@ -109,6 +109,7 @@ TIPS:
                     auth_method,
                     None,
                     None,
+                    None,
                     matches.get_flag("dry-run"),
                     &pagination,
                     None,

src/helpers/docs.rs

@@ -99,6 +99,7 @@ TIPS:
                     auth_method,
                     None,
                     None,
+                    None,
                     matches.get_flag("dry-run"),
                     &pagination,
                     None,

src/helpers/drive.rs

@@ -110,6 +110,7 @@ TIPS:
                     auth_method,
                     None,
                     Some(file_path),
+                    None,
                     matches.get_flag("dry-run"),
                     &executor::PaginationConfig::default(),
                     None,

src/helpers/gmail/mod.rs

@@ -613,6 +613,7 @@ pub(super) async fn send_raw_email(
         auth_method,
         None,
         None,
+        None,
         matches.get_flag("dry-run"),
         &pagination,
         None,

src/helpers/script.rs

@@ -122,6 +122,7 @@ TIPS:
                     auth_method,
                     None,
                     None,
+                    None,
                     matches.get_flag("dry-run"),
                     &executor::PaginationConfig::default(),
                     None,

src/helpers/sheets.rs

@@ -136,6 +136,7 @@ TIPS:
                     auth_method,
                     None,
                     None,
+                    None,
                     matches.get_flag("dry-run"),
                     &pagination,
                     None,
@@ -178,6 +179,7 @@ TIPS:
                     auth_method,
                     None,
                     None,
+                    None,
                     matches.get_flag("dry-run"),
                     &executor::PaginationConfig::default(),
                     None,

src/main.rs

@@ -216,6 +216,11 @@ async fn run() -> Result<(), GwsError> {
         .ok()
         .flatten()
         .map(|s| s.as_str());
+    let upload_content_type = matched_args
+        .try_get_one::<String>("upload-content-type")
+        .ok()
+        .flatten()
+        .map(|s| s.as_str());
 
     let dry_run = matched_args.get_flag("dry-run");
 
@@ -254,6 +259,7 @@ async fn run() -> Result<(), GwsError> {
         auth_method,
         output_path,
         upload_path,
+        upload_content_type,
         dry_run,
         &pagination,
         sanitize_config.template.as_deref(),
@@ -421,6 +427,7 @@ fn print_usage() {
     println!("    --params <JSON>       URL/Query parameters as JSON");
     println!("    --json <JSON>         Request body as JSON (POST/PATCH/PUT)");
     println!("    --upload <PATH>       Local file to upload as media content (multipart)");
+    println!("    --upload-content-type <MIME>  MIME type of the uploaded file (auto-detected from extension if omitted)");
     println!("    --output <PATH>       Output file path for binary responses");
     println!("    --format <FMT>        Output format: json (default), table, yaml, csv");
     println!("    --api-version <VER>   Override the API version (e.g., v2, v3)");