PLA-292 Use cache for rust test workflow

cspell.json

@@ -67,6 +67,7 @@
     "Println",
     "projen",
     "projenrc",
+    "rustc",
     "rustfmt",
     "testid",
     "timestamptz",

src/common/github/__tests__/index.ts

@@ -466,19 +466,38 @@ describe('GitHub utils', () => {
         const {toolchain: toolchainSetup, components} = job.steps[1]!.with!
         expect(toolchainSetup).toEqual('nightly')
         expect(components).toEqual('rustfmt, clippy')
-        const toolchainUse = job.steps[2]!.with!.toolchain
+        const toolchainUse = job.steps[3]!.with!.toolchain
         expect(toolchainUse).toEqual('nightly')
       })
     })
 
+    test('Caches cargo home and target folders', () => {
+      const project = new TestProject()
+      new RustTestWorkflow(project.github!)
+      const snapshot = synthSnapshot(project)
+      const workflow = YAML.parse(snapshot[workflowPath])
+      const jobs = Object.values<projen.github.workflows.Job>(workflow.jobs)
+
+      jobs.forEach((job) => {
+        const cacheStep = job.steps[2]
+        expect(cacheStep.uses).toEqual('actions/cache@v3')
+        const {path, key} = cacheStep.with!
+        expect(path).toContain('\n~/.cargo')
+        expect(path).toContain('\ntarget/')
+        expect(key).toContain('runner.os')
+        expect(key).toContain('steps.toolchain.outputs.rustc_hash')
+        expect(key).toContain("hashFiles('**/Cargo.lock')")
+      })
+    })
+
     test('adds four checks to the workflow', () => {
       const project = new TestProject()
       new RustTestWorkflow(project.github!)
       const snapshot = synthSnapshot(project)
       const workflow = YAML.parse(snapshot[workflowPath])
       const jobs = Object.values<projen.github.workflows.Job>(workflow.jobs)
       expect(jobs).toHaveLength(4)
-      const commands = jobs.map((j) => j.steps[2]!.with!.command)
+      const commands = jobs.map((j) => j.steps[3]!.with!.command)
       expect(commands).toContain('clippy')
       expect(commands).toContain('check')
       expect(commands).toContain('fmt')

src/common/github/rust-test-workflow.ts

@@ -88,9 +88,29 @@ export class RustTestWorkflow extends GithubWorkflow {
           {uses: 'actions/checkout@v3'},
           {
             name: 'Install latest nightly',
+            id: 'toolchain',
             uses: 'actions-rs/toolchain@v1',
             with: {toolchain, components: 'rustfmt, clippy'},
           },
+          {
+            uses: 'actions/cache@v3',
+            with: {
+              path: [
+                '~/.cargo/bin/',
+                '~/.cargo/registry/index/',
+                '~/.cargo/registry/cache/',
+                '~/.cargo/git/db/',
+                'target/',
+              ].join('\n'),
+              key: [
+                'cargo',
+                '${{ runner.os }}',
+                '${{ steps.toolchain.outputs.rustc_hash }}',
+                "${{ hashFiles('**/Cargo.lock') }}",
+                command,
+              ].join('-'),
+            },
+          },
           {
             name: `Run ${command}`,
             uses: 'actions-rs/cargo@v1',