Add variable on global HH env identifying solidity-coverage task (#682)

README.md

@@ -145,6 +145,15 @@ const CoverageAPI = require('solidity-coverage/api');
 
 [Documentation available here][28].
 
+## Detecting solidity-coverage from another task
+
+If you're writing another plugin or task, it can be helpful to detect whether coverage is running or not.
+The coverage plugin sets a boolean variable on the globally injected hardhat environment object for this purpose.
+
+```
+hre.__SOLIDITY_COVERAGE_RUNNING === true
+```
+
 ## FAQ
 
 Common problems & questions:

plugins/hardhat.plugin.js

@@ -96,6 +96,9 @@ task("coverage", "Generates a code coverage report for tests")
   instrumentedSources = {};
   measureCoverage = true;
 
+  // Set a variable on the environment so other tasks can detect if this task is executing
+  env.__SOLIDITY_COVERAGE_RUNNING = true;
+
   try {
     config = nomiclabsUtils.normalizeConfig(env.config, args);
     ui = new PluginUI(config.logger.log);