Add json-file option

README.md

@@ -18,6 +18,9 @@ so hints are displayed as GitHub annotations.
   * `- path: '["src/", "test/"]'`
   * `- path: ${{ toJSON(steps.whatever.changed_dirs) }}` (see: docs on [toJSON](https://docs.github.com/en/actions/reference/context-and-expression-syntax-for-github-actions#tojson))
 * `hlint-bin` (optional): The `hlint` binary path, if not already in `PATH`.
+* `json-file` (optional): If given, the action reads JSON hint output from this
+  file instead of running `hlint` directly. Can be useful for integration with
+  alternate build systems.
 
 ## Outputs
 

action.yml

@@ -12,6 +12,9 @@ inputs:
     description: 'Path or JSON array of paths to check with hlint'
     required: false
     default: '.'
+  json-file:
+    description: 'Existing hlint JSON output file to use instead of running hlint'
+    required: false
 outputs:
   ideas:
     description: 'A JSON array of HLint output ideas (errors, warnings, suggestions, and so on)'

dist/hlint/index.js

@@ -34,18 +34,18 @@ const HLINT_SEV_TO_GITHUB_SEV = {
     Ignore: 'warning',
 };
 /**
- * Use JSON escaping to turn messages with newlines and such into a single line.
+ * Use JSON escaping to turn convert literal newlines to Github Action-supported newlines.
  */
 function escapeString(str, quote) {
-    const jsonEscaped = JSON.stringify(str).replace(/\n/g, ' ');
+    const jsonEscaped = JSON.stringify(str).replace(/\n/g, '%0A');
     // Possibly drop the surrounding quotes
     return quote ? jsonEscaped : jsonEscaped.slice(1, jsonEscaped.length - 1);
 }
 /**
  * Combine the non-"poblemMatcher" fields of an "idea" into
  * a single line as a human-readable message.
  *
- * Fields are visually separated by a box character (' ▫︎ ').
+ * Fields are visually separated by newlines.
  */
 function getNiceMessage(idea) {
     const prefixParts = [];
@@ -68,7 +68,7 @@ function getNiceMessage(idea) {
     if (idea.note && idea.note.length) {
         messageParts.push(`Note: ${idea.note.map(n => escapeString(n, false)).join(' ')}`);
     }
-    const message = messageParts.join(' ▫︎ ');
+    const message = messageParts.join('%0A');
     return [prefix, message].filter(Boolean).join(': ');
 }
 function toMatchableProblem(idea) {