Create the concept of an "unsupported" file

backend-local-server/src/fs.rs

@@ -2,7 +2,7 @@ use std::path::{Path, PathBuf};
 
 use walkdir::{DirEntry, WalkDir};
 
-use crate::{DataInterface, DataReadError, DataSaveError, EntriesToCompare};
+use crate::{DataInterface, DataReadError, DataSaveError, EntriesToCompare, FileEntry};
 
 fn scan(root: &Path) -> impl Iterator<Item = Result<(DirEntry, String), DataReadError>> {
     // As an alternative to WalkDir, see
@@ -120,23 +120,40 @@ pub fn fake_data() -> EntriesToCompare {
         (
             "edited_file",
             [
-                Some("First\nThird\nFourth\nFourthAndAHalf\n\nFifth\nSixth\n----\none two"),
-                Some("First\nSecond\nThird\nFifth\nSixth\n----\none\n"),
+                FileEntry::Text(
+                    "First\nThird\nFourth\nFourthAndAHalf\n\nFifth\nSixth\n----\none two"
+                        .to_string(),
+                ),
+                FileEntry::Text("First\nSecond\nThird\nFifth\nSixth\n----\none\n".to_string()),
+            ],
+        ),
+        (
+            "deleted_file",
+            [FileEntry::Text("deleted".to_string()), FileEntry::Missing],
+        ),
+        (
+            "added file",
+            [FileEntry::Missing, FileEntry::Text("added".to_string())],
+        ),
+        (
+            "unsupported-left",
+            [
+                FileEntry::Unsupported("demo of an unsupported file".to_string()),
+                FileEntry::Text("text".to_string()),
+            ],
+        ),
+        (
+            "unsupported-right",
+            [
+                FileEntry::Text("text".to_string()),
+                FileEntry::Unsupported("demo of an unsupported file".to_string()),
             ],
         ),
-        ("deleted_file", [Some("deleted"), None]),
-        ("added file", [None, Some("added")]),
     ];
-    let optstr = |opt: Option<&str>| opt.map(|s| s.to_string());
     EntriesToCompare(
         two_sides_map
             .into_iter()
-            .map(|(key, [left, right])| {
-                (
-                    PathBuf::from(key),
-                    [optstr(left), optstr(right), optstr(right)],
-                )
-            })
+            .map(|(key, [left, right])| (PathBuf::from(key), [left, right.clone(), right]))
             .collect(),
     )
 }
@@ -160,9 +177,9 @@ fn scan_several(roots: [&PathBuf; 3]) -> Result<EntriesToCompare, DataReadError>
                         )
                     }),
                 ))
-                .or_insert(Default::default())
+                .or_insert([FileEntry::Missing, FileEntry::Missing, FileEntry::Missing])
                 .as_mut();
-            value[i] = Some(contents);
+            value[i] = FileEntry::Text(contents);
         }
     }
     Ok(result)

backend-local-server/src/types.rs

@@ -2,12 +2,21 @@ use std::path::PathBuf;
 
 use thiserror::Error;
 
+#[derive(Debug, Clone, PartialEq, Eq, serde::Serialize, serde::Deserialize)]
+#[serde(tag = "type", content = "value")]
+pub enum FileEntry {
+    Missing,
+    // TODO: Track executable bit, other metadata perhaps
+    Text(String),
+    Unsupported(String),
+}
+
 /// TODO: Clean this up to make things more readable
 const OUTPUT_INDEX: usize = 2;
 #[derive(Debug, Clone, PartialEq, Eq, Default, serde::Serialize, serde::Deserialize)]
 //struct EntriesToCompare<P, const N: usize>(std::collections::BTreeMap<P,
 // [Option<String>; N]>);
-pub struct EntriesToCompare(pub std::collections::BTreeMap<PathBuf, [Option<String>; 3]>);
+pub struct EntriesToCompare(pub std::collections::BTreeMap<PathBuf, [FileEntry; 3]>);
 
 #[derive(Error, Debug)]
 pub enum DataSaveError {
@@ -114,7 +123,7 @@ impl DataInterface for EntriesToCompare {
             self.0
                 .get_mut(&PathBuf::from(path))
                 .expect("At this point, `save()` should have verified that the path is valid")
-                [OUTPUT_INDEX] = Some(new_value);
+                [OUTPUT_INDEX] = FileEntry::Text(new_value);
         }
         Ok(())
     }

webapp/src/backend_interactions.ts

@@ -1,13 +1,25 @@
 import { InvokeArgs, invoke as tauriInvoke } from "@tauri-apps/api/tauri";
 import { exit as tauriExit } from "@tauri-apps/api/process";
 
-type SingleFileMergeInput = {
-  left: string | null;
-  right: string | null;
-  edit: string | null;
+export type FileEntry =
+  | { type: "Missing" }
+  | { type: "Text"; value: string }
+  | { type: "Unsupported"; value: string };
+export type SingleFileMergeInput = {
+  left: FileEntry;
+  right: FileEntry;
+  edit: FileEntry;
 };
 export type MergeInput = Record<string, SingleFileMergeInput>;
 
+export function to_text(file_entry: FileEntry): string | null {
+  if (file_entry.type == "Text") {
+    return file_entry.value;
+  } else {
+    return null;
+  }
+}
+
 // Tauri interop
 
 // https://github.com/tauri-apps/tauri/discussions/6119

webapp/src/main.ts

@@ -12,6 +12,8 @@ import {
   exit_success,
   TAURI_BACKEND,
   exit_user_abandoned_merge,
+  SingleFileMergeInput,
+  to_text,
 } from "./backend_interactions";
 
 class MergeState {
@@ -24,6 +26,7 @@ class MergeState {
   values(): Record<string, string> {
     let result: Record<string, string> = {};
     for (let k in this.merge_views) {
+      // TODO: Treat deleted values properly
       result[k] = this.merge_views[k].editor().getValue();
     }
     return result;
@@ -39,37 +42,62 @@ class MergeState {
 function render_input(unique_id: string, merge_input: MergeInput) {
   let templates = [];
   let k_uid = (k: string) => `${k}_${unique_id}`;
+  let to_error = (input: SingleFileMergeInput) => {
+    let unsupported_value = Array.from([
+      { file: input.left, side: "left" },
+      { file: input.right, side: "right" },
+      { file: input.edit, side: "middle" },
+    ]).find((v) => v.file.type == "Unsupported");
+    if (unsupported_value == null) {
+      return null;
+    } else if (unsupported_value.file.type != "Unsupported") {
+      throw new Error("this statement is unreachable; this check exists to make TS happy");
+    }
+    return html`<b>error</b>: ${unsupported_value.file.value} (occurred on the
+      ${unsupported_value.side} side)`;
+  };
+
   for (let k in merge_input) {
-    templates.push(html`
-      <details open id="details_${k_uid(k)}">
-        <!-- We will close this with javascript shortly. See below. -->
-        <summary>
-          <code>${k}</code>
-          <button id="collapse_${k_uid(k)}" hidden>
-            (Un)Collapse (Doesn't work)
-          </button>
-          <button
-            id="prevChange_${k_uid(k)}"
-            alt="Previous Change"
-            title="Previous Change"
-          >
-            ⇧ Previous Change
-          </button>
-          <button
-            id="nextChange_${k_uid(k)}"
-            alt="Next Change"
-            title="Next Change"
-          >
-            ⇩ Next Change
-          </button>
-          <button id="linewrap_${k_uid(k)}" hidden>
-            <!--Buggy with collapseIdentical, see comment below -->
-            (Un)Wrap Lines
-          </button>
-        </summary>
-        <div id="cm_${k_uid(k)}"></div>
-      </details>
-    `);
+    let error = to_error(merge_input[k]);
+    if (error != null) {
+      templates.push(html` <details id="details_${k_uid(k)}">
+        <summary><code>${k}</code>: ${error}</summary>
+        <!-- TODO: Allow inserting error details here, perhaps grey out the triangle
+          -- if there are no details.
+          -->
+      </details>`);
+    } else {
+      templates.push(html`
+        <details open id="details_${k_uid(k)}">
+          <!-- We will close this with javascript shortly. See below. -->
+          <summary>
+            <code>${k}</code>
+            <button id="collapse_${k_uid(k)}" hidden>
+              (Un)Collapse (Doesn't work)
+            </button>
+            <button
+              id="prevChange_${k_uid(k)}"
+              alt="Previous Change"
+              title="Previous Change"
+            >
+              ⇧ Previous Change
+            </button>
+            <button
+              id="nextChange_${k_uid(k)}"
+              alt="Next Change"
+              title="Next Change"
+            >
+              ⇩ Next Change
+            </button>
+            <button id="linewrap_${k_uid(k)}" hidden>
+              <!--Buggy with collapseIdentical, see comment below -->
+              (Un)Wrap Lines
+            </button>
+          </summary>
+          <div id="cm_${k_uid(k)}"></div>
+        </details>
+      `);
+    }
   }
 
   let target_element = document.getElementById(unique_id)!;
@@ -78,6 +106,9 @@ function render_input(unique_id: string, merge_input: MergeInput) {
 
   let merge_views: Record<string, MergeView> = {};
   for (let k in merge_input) {
+    if (to_error(merge_input[k]) != null) {
+      continue;
+    }
     let collapseButtonEl = document.getElementById(`collapse_${k_uid(k)}`)!;
     let linewrapButtonEl = document.getElementById(`linewrap_${k_uid(k)}`)!;
     let prevChangeButtonEl = document.getElementById(`prevChange_${k_uid(k)}`)!;
@@ -88,9 +119,9 @@ function render_input(unique_id: string, merge_input: MergeInput) {
     let cmEl = document.getElementById(`cm_${k_uid(k)}`)!;
 
     let config = {
-      value: merge_input[k].edit ?? "",
-      origLeft: merge_input[k].left ?? "", // Set to null for 2 panes
-      orig: merge_input[k].right ?? "",
+      value: to_text(merge_input[k].edit) ?? "",
+      origLeft: to_text(merge_input[k].left) ?? "", // Set to null for 2 panes
+      orig: to_text(merge_input[k].right) ?? "",
       lineNumbers: true,
       /* TODO: Toggling line wrapping breaks `collapseIdentical`. Need a
       settings system where the user can decide whether they want line wrapping,