Development.md

-wip
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+# Development
+
+Plugin source code is in folder `PreCourlis`.
+
+Recommended development environment is Linux.
+You can also use Windows but you'll not have the help of `make` targets.
+
+Automated tests suite can be run with Docker on any Linux operating system.
+
+
+## Build development docker image
+
+```bash
+make build
+```
+
+This will build the docker image named `camptocamp/edf-precourlis-builder` and
+build or retrieve some runtime files:
+
+- PreCourlis/ui/resources_rc.py  (generated from PreCourlis/resources/resources.qrc)
+- PreCourlis/lib/TatooineMesher  (cloned from https://github.com/arnaud-morvan/TatooineMesher/tree/PreCourlis)
+
+This image will be later used to run a QGIS desktop application in a adapted environment or to run automated tests suite.
+
+
+## debugging with VS Code
+
+When QGIS desktop is started with Docker (`make qgis`), or when `debugpy` is available from QGIS Python process, PreCourlis plugin automatically create a menu action to make debugpy listen on port 5679 and wait for client.
+
+When tests are run with target `test-debug`, the tests session first make debugpy listen on host port 5680 and wait for client before running any test. You will have to connect to running `debugpy` server from VS Code before any test start.
+
+```bash
+make test-debug
+```
+
+Then in VS Code configure your `launch.json` file with something like:
+
+```json
+{
+    // Use IntelliSense to learn about possible attributes.
+    // Hover to view descriptions of existing attributes.
+    // For more information, visit: https://go.microsoft.com/fwlink/?linkid=830387
+    "version": "0.2.0",
+    "configurations": [
+        {
+            "name": "Python: QGIS",
+            "type": "python",
+            "request": "attach",
+            "connect": {
+                "host": "localhost",
+                "port": 5679
+            },
+            "pathMappings": [
+                {
+                    "localRoot": "${workspaceFolder}",
+                    "remoteRoot": "/app"
+                }
+            ],
+            "justMyCode": true
+        },
+        {
+            "name": "Python: Tests",
+            "type": "python",
+            "request": "attach",
+            "connect": {
+                "host": "localhost",
+                "port": 5680
+            },
+            "pathMappings": [
+                {
+                    "localRoot": "${workspaceFolder}",
+                    "remoteRoot": "/app"
+                }
+            ],
+            "justMyCode": true
+        }
+    ]
+}
+```
+
+And now you can easily connect to the Python process from VS Code for debugging.
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