feat: Diagnose failure to follow dfx 0.11 upgrade steps (dfinity#3199)

If  project was last deployed with dfx <= 0.10, and upgrade steps for dfx 0.11 were not followed, `dfx deploy` with dfx >= 0.11 will fail with an error about duplicate assets.  This PR makes dfx detect this case and display upgrade steps.

Fixes https://dfinity.atlassian.net/browse/SDK-870

CHANGELOG.md

@@ -27,6 +27,10 @@ The custom build command can be set in `dfx.json` the same way it is set for `cu
 }
 ```
 
+### fix: Diagnose duplicate assets and display upgrade steps
+
+If `dfx deploy` detects duplicate assets in the dist/ and frontend assets/ directories, it will now suggest upgrade steps.
+
 ### fix: motoko canisters can import other canisters with service constructor
 
 After specific canister builder output wasm and candid file, `dfx` will do some post processing on the candid file.

e2e/tests-dfx/error_diagnosis.bash

@@ -12,6 +12,20 @@ teardown() {
     standard_teardown
 }
 
+@test "Duplicate assets in dist/ from src/" {
+    dfx_new_frontend hello
+    install_asset greet
+    dfx_start
+    assert_command dfx deploy
+
+    # simulate previous deploy with CopyPlugin step
+    cp src/hello_frontend/assets/* dist/hello_frontend/
+
+    assert_command_fail dfx deploy
+    assert_contains "Remove the CopyPlugin step from webpack.config.js"
+    assert_contains "Delete all files from the dist/ directory"
+}
+
 @test "HTTP 403 has a full diagnosis" {
     dfx_new hello
     install_asset greet

src/dfx/src/lib/diagnosis.rs

@@ -2,6 +2,9 @@ use crate::lib::error_code;
 use anyhow::Error as AnyhowError;
 use ic_agent::agent::{RejectCode, RejectResponse};
 use ic_agent::AgentError;
+use ic_asset::error::{GatherAssetDescriptorsError, SyncError, UploadContentError};
+use regex::Regex;
+use std::path::Path;
 use thiserror::Error as ThisError;
 
 use super::environment::Environment;
@@ -49,6 +52,12 @@ pub fn diagnose(_env: &dyn Environment, err: &AnyhowError) -> Diagnosis {
         }
     }
 
+    if let Some(sync_error) = err.downcast_ref::<SyncError>() {
+        if duplicate_asset_key_dist_and_src(sync_error) {
+            return diagnose_duplicate_asset_key_dist_and_src();
+        }
+    }
+
     NULL_DIAGNOSIS
 }
 
@@ -90,3 +99,49 @@ The most common way this error is solved is by running 'dfx canister update-sett
         Some(action_suggestion.to_string()),
     )
 }
+
+fn duplicate_asset_key_dist_and_src(sync_error: &SyncError) -> bool {
+    fn is_src_to_dist(path0: &Path, path1: &Path) -> bool {
+        // .../dist/<canister name>/... and .../src/<canister name>/assets/...
+        let path0 = path0.to_string_lossy();
+        let path1 = path1.to_string_lossy();
+        let re = Regex::new(r"(?P<project_dir>.*)/dist/(?P<canister>[^/]*)/(?P<rest>.*)").unwrap();
+
+        if let Some(caps) = re.captures(&path0) {
+            let project_dir = caps["project_dir"].to_string();
+            let canister = caps["canister"].to_string();
+            let rest = caps["rest"].to_string();
+            let transformed = format!("{}/src/{}/assets/{}", project_dir, canister, rest);
+            return transformed == path1;
+        }
+        false
+    }
+    matches!(sync_error,
+        SyncError::UploadContentFailed(
+            UploadContentError::GatherAssetDescriptorsFailed(
+                GatherAssetDescriptorsError::DuplicateAssetKey(_key, path0, path1)))
+        if is_src_to_dist(path0, path1)
+    )
+}
+
+fn diagnose_duplicate_asset_key_dist_and_src() -> Diagnosis {
+    let explanation = "An asset key was found in both the dist and src directories.
+One or both of the following are a likely explanation:
+    - webpack.config.js is configured to copy assets from the src directory to the dist/ directory.
+    - there are leftover files in the dist/ directory from a previous build.";
+    let suggestion = r#"Perform the following steps:
+    1. Remove the CopyPlugin step from webpack.config.js.  It looks like this:
+        new CopyPlugin({
+              patterns: [
+                {
+                  from: path.join(__dirname, "src", frontendDirectory, "assets"),
+                  to: path.join(__dirname, "dist", frontendDirectory),
+                },
+              ],
+            }),
+    2. Delete all files from the dist/ directory."
+
+See also release notes: https://forum.dfinity.org/t/dfx-0-11-0-is-promoted-with-breaking-changes/14327"#;
+
+    (Some(explanation.to_string()), Some(suggestion.to_string()))
+}