Add backend tests for critical coverage gaps in expand.ts, proc.ts, and contextKeyExpr.ts (#4852)

* Add backend tests for expand.ts, proc.ts, and contextKeyExpr.ts

- expand.test.ts: 23 tests for substituteAll(), getParentEnvSubstitutions(), errorHandlerHelper()
- buildCmdStr.test.ts: 16 tests for buildCmdStr() command string construction
- contextKeyExpr.test.ts: 69 tests for Parser, evaluation, serialization, and utility functions
- All 187 backend tests pass, TypeScript compilation clean

Agent-Logs-Url: https://github.com/microsoft/vscode-cmake-tools/sessions/f669e0ca-6ea1-4eae-9eb6-2c78ee6377c9

Co-authored-by: hanniavalera <[email protected]>

* Clarify didReplacement test comment per code review feedback

Agent-Logs-Url: https://github.com/microsoft/vscode-cmake-tools/sessions/f669e0ca-6ea1-4eae-9eb6-2c78ee6377c9

Co-authored-by: hanniavalera <[email protected]>

* no need for changelog as it is mainly tests

---------

Co-authored-by: copilot-swe-agent[bot] <[email protected]>
Co-authored-by: hanniavalera <[email protected]>
Co-authored-by: Hannia Valera <[email protected]>

Author: 3 people

test/unit-tests/backend/buildCmdStr.test.ts

@@ -0,0 +1,108 @@
+import { expect } from 'chai';
+
+/**
+ * Tests for the buildCmdStr() function from src/proc.ts.
+ *
+ * This function constructs a human-readable command string from a command and
+ * its arguments, quoting any arguments that contain whitespace or special characters.
+ * It is used for logging executed commands to the output panel.
+ *
+ * The function is mirrored here because proc.ts transitively depends on 'vscode',
+ * which cannot be imported in backend tests.
+ */
+
+// --- Mirror of proc.buildCmdStr ---
+function buildCmdStr(command: string, args?: string[]): string {
+    let cmdarr = [command];
+    if (args) {
+        cmdarr = cmdarr.concat(args);
+    }
+    return cmdarr.map(a => /[ \n\r\f;\t]/.test(a) ? `"${a}"` : a).join(' ');
+}
+
+suite('[buildCmdStr]', () => {
+
+    test('Command with no arguments', () => {
+        const result = buildCmdStr('cmake');
+        expect(result).to.equal('cmake');
+    });
+
+    test('Command with simple arguments', () => {
+        const result = buildCmdStr('cmake', ['--build', '.', '--target', 'all']);
+        expect(result).to.equal('cmake --build . --target all');
+    });
+
+    test('Argument with spaces is quoted', () => {
+        const result = buildCmdStr('cmake', ['-S', '/path with spaces/src']);
+        expect(result).to.equal('cmake -S "/path with spaces/src"');
+    });
+
+    test('Command itself with spaces is quoted', () => {
+        const result = buildCmdStr('/Program Files/CMake/bin/cmake', ['--version']);
+        expect(result).to.equal('"/Program Files/CMake/bin/cmake" --version');
+    });
+
+    test('Argument with tab is quoted', () => {
+        const result = buildCmdStr('cmake', ['-DVAR=value\twith\ttabs']);
+        expect(result).to.equal('cmake "-DVAR=value\twith\ttabs"');
+    });
+
+    test('Argument with newline is quoted', () => {
+        const result = buildCmdStr('cmake', ['-DVAR=line1\nline2']);
+        expect(result).to.equal('cmake "-DVAR=line1\nline2"');
+    });
+
+    test('Argument with carriage return is quoted', () => {
+        const result = buildCmdStr('cmake', ['-DVAR=line1\rline2']);
+        expect(result).to.equal('cmake "-DVAR=line1\rline2"');
+    });
+
+    test('Argument with form feed is quoted', () => {
+        const result = buildCmdStr('cmake', ['-DVAR=value\fmore']);
+        expect(result).to.equal('cmake "-DVAR=value\fmore"');
+    });
+
+    test('Argument with semicolon is quoted', () => {
+        const result = buildCmdStr('cmake', ['-DCMAKE_PREFIX_PATH=/a;/b;/c']);
+        expect(result).to.equal('cmake "-DCMAKE_PREFIX_PATH=/a;/b;/c"');
+    });
+
+    test('Mixed quoted and unquoted arguments', () => {
+        const result = buildCmdStr('cmake', ['--build', '/path with space', '--config', 'Release']);
+        expect(result).to.equal('cmake --build "/path with space" --config Release');
+    });
+
+    test('Empty arguments list', () => {
+        const result = buildCmdStr('cmake', []);
+        expect(result).to.equal('cmake');
+    });
+
+    test('Undefined arguments', () => {
+        const result = buildCmdStr('cmake', undefined);
+        expect(result).to.equal('cmake');
+    });
+
+    test('Multiple CMake-style define arguments', () => {
+        const result = buildCmdStr('cmake', [
+            '-DCMAKE_BUILD_TYPE=Debug',
+            '-DCMAKE_INSTALL_PREFIX=/usr/local',
+            '-DBUILD_SHARED_LIBS=ON'
+        ]);
+        expect(result).to.equal('cmake -DCMAKE_BUILD_TYPE=Debug -DCMAKE_INSTALL_PREFIX=/usr/local -DBUILD_SHARED_LIBS=ON');
+    });
+
+    test('Windows path with backslashes is not quoted (no special chars)', () => {
+        const result = buildCmdStr('C:\\CMake\\bin\\cmake.exe', ['--version']);
+        expect(result).to.equal('C:\\CMake\\bin\\cmake.exe --version');
+    });
+
+    test('Argument that is just a space is quoted', () => {
+        const result = buildCmdStr('echo', [' ']);
+        expect(result).to.equal('echo " "');
+    });
+
+    test('Arguments preserving cmake --install pattern', () => {
+        const result = buildCmdStr('cmake', ['--install', '/build/dir', '--config', 'Release', '--prefix', '/opt/install path']);
+        expect(result).to.equal('cmake --install /build/dir --config Release --prefix "/opt/install path"');
+    });
+});