Refactor support for multiple Meson projects

There were many issues, including:
- The most common case is to have a meson.build at the root of the
  workspace. In that case we should not ask user anything.
- Only the first meson.build in a subdir tree is useful, others are
  unlikely to be projects.
- We need a way to never ask again to select a meson file, especially
  important when opening meson project itself which does not have a
  meson.build at the root, but many projects in test cases.
- If the user cancels selection, the meson extension cannot do anything
  and should be hidden.
- Selecting a meson file and configuring the project are 2 distinct
  questions. The user may want to select a file but not let vscode
  configure it. It is common to configure from an external terminal.

package.json

@@ -87,11 +87,20 @@
       {
         "command": "mesonbuild.restartLanguageServer",
         "title": "Meson: Restart Language Server"
+      },
+      {
+        "command": "mesonbuild.selectRootDir",
+        "title": "Meson: Select another project root dir"
       }
     ],
     "configuration": {
       "title": "Meson build configuration",
       "properties": {
+        "mesonbuild.selectRootDir": {
+          "type": "boolean",
+          "default": true,
+          "description": "Should Meson ask to select a Meson project root directory when more than one project is detected."
+        },
         "mesonbuild.configureOnOpen": {
           "type": [
             "boolean",
@@ -405,6 +414,42 @@
         {
           "command": "mesonbuild.openBuildFile",
           "when": "false"
+        },
+        {
+          "command": "mesonbuild.reconfigure",
+          "when": "mesonbuild.hasProject"
+        },
+        {
+          "command": "mesonbuild.clean",
+          "when": "mesonbuild.hasProject"
+        },
+        {
+          "command": "mesonbuild.build",
+          "when": "mesonbuild.hasProject"
+        },
+        {
+          "command": "mesonbuild.test",
+          "when": "mesonbuild.hasProject"
+        },
+        {
+          "command": "mesonbuild.run",
+          "when": "mesonbuild.hasProject"
+        },
+        {
+          "command": "mesonbuild.install",
+          "when": "mesonbuild.hasProject"
+        },
+        {
+          "command": "mesonbuild.benchmark",
+          "when": "mesonbuild.hasProject"
+        },
+        {
+          "command": "mesonbuild.restartLanguageServer",
+          "when": "mesonbuild.hasProject"
+        },
+        {
+          "command": "mesonbuild.selectRootDir",
+          "when": "mesonbuild.hasMultipleProjects"
         }
       ]
     },

src/dialogs.ts

@@ -0,0 +1,115 @@
+import * as vscode from "vscode";
+import { relative } from "path";
+import { extensionConfiguration, extensionConfigurationSet } from "./utils";
+import { SettingsKey } from "./types";
+
+export async function askConfigureOnOpen(): Promise<boolean> {
+  let configureOnOpen = extensionConfiguration(SettingsKey.configureOnOpen);
+
+  if (typeof configureOnOpen === "boolean") return configureOnOpen;
+
+  enum Options {
+    yes = "Yes",
+    always = "Always",
+    no = "No",
+    never = "Never",
+  }
+
+  const response = await vscode.window.showInformationMessage(
+    "Meson project detected in this workspace but does not seems to be configured. Would you like VS Code to configure it?",
+    ...Object.values(Options),
+  );
+
+  switch (response) {
+    case Options.no:
+      return false;
+    case Options.never:
+      extensionConfigurationSet(SettingsKey.configureOnOpen, false, vscode.ConfigurationTarget.Workspace);
+      return false;
+    case Options.yes:
+      return true;
+    case Options.always:
+      extensionConfigurationSet(SettingsKey.configureOnOpen, true, vscode.ConfigurationTarget.Workspace);
+      return true;
+  }
+
+  return false;
+}
+
+export async function askShouldDownload(): Promise<boolean> {
+  const downloadLanguageServer = extensionConfiguration(SettingsKey.downloadLanguageServer);
+
+  if (typeof downloadLanguageServer === "boolean") return downloadLanguageServer;
+
+  enum Options {
+    yes = "Yes",
+    no = "Not this time",
+    never = "Never",
+  }
+
+  const response = await vscode.window.showInformationMessage(
+    "Should the extension try to download the language server?",
+    ...Object.values(Options),
+  );
+
+  switch (response) {
+    case Options.yes:
+      extensionConfigurationSet(SettingsKey.downloadLanguageServer, true, vscode.ConfigurationTarget.Global);
+      return true;
+    case Options.never:
+      extensionConfigurationSet(SettingsKey.downloadLanguageServer, false, vscode.ConfigurationTarget.Global);
+      return false;
+    case Options.no:
+      return false;
+  }
+
+  return false;
+}
+
+export async function askSelectRootDir(): Promise<boolean> {
+  const selectRootDir = extensionConfiguration(SettingsKey.selectRootDir);
+
+  if (!selectRootDir) return false;
+
+  enum Options {
+    yes = "Yes",
+    no = "No",
+    never = "Never",
+  }
+
+  const response = await vscode.window.showInformationMessage(
+    "Multiple Meson projects detected, select one?",
+    ...Object.values(Options),
+  );
+
+  switch (response) {
+    case Options.yes:
+      return true;
+    case Options.no:
+      return false;
+    case Options.never:
+      extensionConfigurationSet(SettingsKey.selectRootDir, false, vscode.ConfigurationTarget.Workspace);
+      return false;
+  }
+
+  return false;
+}
+
+export async function selectRootDir(rootDirs: string[]): Promise<string | undefined> {
+  // TODO: What label to use when there is more than one workspace?
+  const root = vscode.workspace.rootPath ?? "";
+  const items = rootDirs.map((file, index) => ({ index: index, label: relative(root, file) }));
+  items.sort((a, b) => a.label.localeCompare(b.label));
+  const selection = await vscode.window.showQuickPick(items, {
+    canPickMany: false,
+    title: "Select configuration to use.",
+    placeHolder: "path/to/meson.build",
+  });
+  if (selection) return rootDirs[selection.index];
+  return undefined;
+}
+
+export async function askAndSelectRootDir(rootDirs: string[]): Promise<string | undefined> {
+  if (await askSelectRootDir()) return selectRootDir(rootDirs);
+  return undefined;
+}