Make dc_get_info() work on a closed context

There is very little API guarantees about this, but clients seem to
expect *something* to work on a closed context.  So split this up into
static info an more dynamic context-related info, but let's not
provide any guarantees about what keys are available when.

Fixes #599

deltachat-ffi/deltachat.h

@@ -405,9 +405,14 @@ char*           dc_get_config                (dc_context_t* context, const char*
 
 /**
  * Get information about the context.
+ *
  * The information is returned by a multi-line string
  * and contains information about the current configuration.
  *
+ * If the context is not open or configured only a subset of the information
+ * will be available.  There is no guarantee about which information will be
+ * included when however.
+ *
  * @memberof dc_context_t
  * @param context The context as created by dc_context_new().
  * @return String which must be free()'d after usage.  Never returns NULL.

deltachat-ffi/src/lib.rs

@@ -347,9 +347,12 @@ pub unsafe extern "C" fn dc_get_info(context: *mut dc_context_t) -> *mut libc::c
         return dc_strdup(ptr::null());
     }
     let ffi_context = &*context;
-    ffi_context
-        .with_inner(|ctx| render_info(ctx.get_info()).unwrap_or_default().strdup())
-        .unwrap_or_else(|_| "".strdup())
+    let guard = ffi_context.inner.read().unwrap();
+    let info = match guard.as_ref() {
+        Some(ref ctx) => ctx.get_info(),
+        None => context::get_info(),
+    };
+    render_info(info).unwrap_or_default().strdup()
 }
 
 fn render_info(

python/tests/test_lowlevel.py

@@ -108,3 +108,25 @@ def test_provider_info():
 
 def test_provider_info_none():
     assert lib.dc_provider_new_from_email(cutil.as_dc_charpointer("email@unexistent.no")) == ffi.NULL
+
+
+def test_get_info_closed():
+    ctx = ffi.gc(
+        lib.dc_context_new(lib.py_dc_callback, ffi.NULL, ffi.NULL),
+        lib.dc_context_unref,
+    )
+    info = cutil.from_dc_charpointer(lib.dc_get_info(ctx))
+    assert 'deltachat_core_version' in info
+    assert 'database_dir' not in info
+
+
+def test_get_info_open(tmpdir):
+    ctx = ffi.gc(
+        lib.dc_context_new(lib.py_dc_callback, ffi.NULL, ffi.NULL),
+        lib.dc_context_unref,
+    )
+    db_fname = tmpdir.join("test.db")
+    lib.dc_open(ctx, db_fname.strpath.encode("ascii"), ffi.NULL)
+    info = cutil.from_dc_charpointer(lib.dc_get_info(ctx))
+    assert 'deltachat_core_version' in info
+    assert 'database_dir' in info

src/context.rs

@@ -66,6 +66,30 @@ pub struct RunningState {
     pub shall_stop_ongoing: bool,
 }
 
+/// Return some info about deltachat-core
+///
+/// This contains information mostly about the library itself, the
+/// actual keys and their values which will be present are not
+/// guaranteed.  Calling [Context::get_info] also includes information
+/// about the context on top of the information here.
+pub fn get_info() -> HashMap<&'static str, String> {
+    let mut res = HashMap::new();
+    res.insert("deltachat_core_version", format!("v{}", &*DC_VERSION_STR));
+    res.insert("sqlite_version", rusqlite::version().to_string());
+    res.insert(
+        "sqlite_thread_safe",
+        unsafe { rusqlite::ffi::sqlite3_threadsafe() }.to_string(),
+    );
+    res.insert(
+        "arch",
+        (::std::mem::size_of::<*mut libc::c_void>())
+            .wrapping_mul(8)
+            .to_string(),
+    );
+    res.insert("level", "awesome".into());
+    res
+}
+
 impl Context {
     pub fn new(cb: Box<ContextCallback>, os_name: String, dbfile: PathBuf) -> Result<Context> {
         let mut blob_fname = OsString::new();
@@ -209,19 +233,7 @@ impl Context {
             .get_config(self, "configured_mvbox_folder")
             .unwrap_or_else(|| "<unset>".to_string());
 
-        let mut res = HashMap::new();
-        res.insert("deltachat_core_version", format!("v{}", &*DC_VERSION_STR));
-        res.insert("sqlite_version", rusqlite::version().to_string());
-        res.insert(
-            "sqlite_thread_safe",
-            unsafe { rusqlite::ffi::sqlite3_threadsafe() }.to_string(),
-        );
-        res.insert(
-            "arch",
-            (::std::mem::size_of::<*mut libc::c_void>())
-                .wrapping_mul(8)
-                .to_string(),
-        );
+        let mut res = get_info();
         res.insert("number_of_chats", chats.to_string());
         res.insert("number_of_chat_messages", real_msgs.to_string());
         res.insert("messages_in_contact_requests", deaddrop_msgs.to_string());
@@ -251,7 +263,6 @@ impl Context {
             pub_key_cnt.unwrap_or_default().to_string(),
         );
         res.insert("fingerprint", fingerprint_str);
-        res.insert("level", "awesome".into());
 
         res
     }
@@ -504,6 +515,14 @@ mod tests {
         let t = dummy_context();
 
         let info = t.ctx.get_info();
+        assert!(info.get("database_dir").is_some());
+    }
+
+    #[test]
+    fn test_get_info_no_context() {
+        let info = get_info();
+        assert!(info.get("deltachat_core_version").is_some());
+        assert!(info.get("database_dir").is_none());
         assert_eq!(info.get("level").unwrap(), "awesome");
     }
 }