fix(broccoli): Modification of the output does not throw on rebuild.

Author: amiller-gh

Diff for: packages/@css-blocks/broccoli/src/Analyze.ts

@@ -75,6 +75,9 @@ export class CSSBlocksAnalyze extends BroccoliPlugin {
     let newFsTree = FSTree.fromEntries(walkSync.entries(input));
     let diff = this.previousInput.calculatePatch(newFsTree);
     if (!diff.length) { return; }
+
+    // Save the current state of our output dir for future diffs.
+    this.previousOutput = FSTree.fromEntries(walkSync.entries(output));
     FSTree.applyPatch(input, output, this.previousOutput.calculatePatch(newFsTree));
     this.previousInput = newFsTree;
 
@@ -122,9 +125,6 @@ export class CSSBlocksAnalyze extends BroccoliPlugin {
       }
     }
 
-    // Save the current state of our output dir for future diffs.
-    this.previousOutput = FSTree.fromEntries(walkSync.entries(output));
-
     // Add each Analysis to the Optimizer.
     this.analyzer.eachAnalysis((a) => optimizer.addAnalysis(a.forOptimizer(options)));
 

Diff for: packages/@css-blocks/broccoli/test/Analyze.ts

@@ -1,4 +1,5 @@
 import * as assert from "assert";
+import * as fs from "fs";
 
 import { GlimmerAnalyzer } from "@css-blocks/glimmer";
 
@@ -80,6 +81,8 @@ describe("Broccoli Analyze Plugin Test", function () {
       });
 
       // Modifications to block files trigger build but result in no output tree changes.
+      // Accidental modification of output directory does not make the plugin explode.
+      fs.unlinkSync(output.path("src/ui/components/Chrisrng/template.hbs"));
       input.write({
         src: { ui: { components: { [entryComponentName]: {
           "stylesheet.css": `:scope { color: blue; } .foo { color: yellow; }`,