From fab017e0e143bb87979f37f422006bb3d3620f5d Mon Sep 17 00:00:00 2001
From: Andreas Abel <andreas.abel@ifi.lmu.de>
Date: Tue, 3 Jan 2023 20:51:30 +0100
Subject: [PATCH 01/10] Fix #29: new input 'cabal-update: false' to turn off
 'cabal update'

---
 setup/action.yml           | 12 ++++++++----
 setup/dist/index.js        |  6 ++++--
 setup/lib/opts.d.ts        |  4 +++-
 setup/lib/opts.js          |  4 +++-
 setup/lib/setup-haskell.js |  2 +-
 setup/src/opts.ts          |  6 ++++--
 setup/src/setup-haskell.ts |  2 +-
 7 files changed, 24 insertions(+), 12 deletions(-)

diff --git a/setup/action.yml b/setup/action.yml
index 87df2eeb..02128abe 100644
--- a/setup/action.yml
+++ b/setup/action.yml
@@ -16,16 +16,20 @@ inputs:
     default: 'latest'
   enable-stack:
     required: false
-    description: 'If specified, will setup Stack'
+    description: 'If specified, will setup Stack.'
   stack-no-global:
     required: false
-    description: 'If specified, enable-stack must be set. Prevents installing GHC and Cabal globally'
+    description: 'If specified, enable-stack must be set. Prevents installing GHC and Cabal globally.'
   stack-setup-ghc:
     required: false
-    description: 'If specified, enable-stack must be set. Will run stack setup to install the specified GHC'
+    description: 'If specified, enable-stack must be set. Will run stack setup to install the specified GHC.'
+  cabal-update:
+    required: false
+    default: true
+    description: 'Set to false to prevent `cabal update` from being run.'
   disable-matcher:
     required: false
-    description: 'If specified, disables match messages from GHC as GitHub CI annotations'
+    description: 'If specified, disables match messages from GHC as GitHub CI annotations.'
 outputs:
   ghc-path:
     description: 'The path of the ghc executable _directory_'
diff --git a/setup/dist/index.js b/setup/dist/index.js
index 000e479b..ef10d587 100644
--- a/setup/dist/index.js
+++ b/setup/dist/index.js
@@ -13698,6 +13698,7 @@ function getOpts({ ghc, cabal, stack }, os, inputs) {
     const stackSetupGhc = (inputs['stack-setup-ghc'] || '') !== '';
     const stackEnable = (inputs['enable-stack'] || '') !== '';
     const matcherDisable = (inputs['disable-matcher'] || '') !== '';
+    const cabalUpdate = inputs['cabal-update'] !== 'false';
     core.debug(`${stackNoGlobal}/${stackSetupGhc}/${stackEnable}`);
     const verInpt = {
         ghc: inputs['ghc-version'] || ghc.version,
@@ -13727,7 +13728,8 @@ function getOpts({ ghc, cabal, stack }, os, inputs) {
             raw: verInpt.cabal,
             resolved: resolve(verInpt.cabal, cabal.supported, 'cabal', os, cabalEnable // if true: inform user about resolution
             ),
-            enable: cabalEnable
+            enable: cabalEnable,
+            update: cabalUpdate
         },
         stack: {
             raw: verInpt.stack,
@@ -13831,7 +13833,7 @@ async function run(inputs) {
                     // https://github.com/haskell/cabal/issues/6823
                     // await exec('cabal user-config update');
                 }
-                if (!opts.stack.enable)
+                if (opts.cabal.update && !opts.stack.enable)
                     await (0, exec_1.exec)('cabal update');
             });
         core.info(`##[add-matcher]${path.join(__dirname, '..', 'matcher.json')}`);
diff --git a/setup/lib/opts.d.ts b/setup/lib/opts.d.ts
index 0c0937e9..cf66dedb 100644
--- a/setup/lib/opts.d.ts
+++ b/setup/lib/opts.d.ts
@@ -14,7 +14,9 @@ export interface ProgramOpt {
 }
 export interface Options {
     ghc: ProgramOpt;
-    cabal: ProgramOpt;
+    cabal: ProgramOpt & {
+        update: boolean;
+    };
     stack: ProgramOpt & {
         setup: boolean;
     };
diff --git a/setup/lib/opts.js b/setup/lib/opts.js
index 6dce63e3..d84b15ff 100644
--- a/setup/lib/opts.js
+++ b/setup/lib/opts.js
@@ -75,6 +75,7 @@ function getOpts({ ghc, cabal, stack }, os, inputs) {
     const stackSetupGhc = (inputs['stack-setup-ghc'] || '') !== '';
     const stackEnable = (inputs['enable-stack'] || '') !== '';
     const matcherDisable = (inputs['disable-matcher'] || '') !== '';
+    const cabalUpdate = inputs['cabal-update'] !== 'false';
     core.debug(`${stackNoGlobal}/${stackSetupGhc}/${stackEnable}`);
     const verInpt = {
         ghc: inputs['ghc-version'] || ghc.version,
@@ -104,7 +105,8 @@ function getOpts({ ghc, cabal, stack }, os, inputs) {
             raw: verInpt.cabal,
             resolved: resolve(verInpt.cabal, cabal.supported, 'cabal', os, cabalEnable // if true: inform user about resolution
             ),
-            enable: cabalEnable
+            enable: cabalEnable,
+            update: cabalUpdate
         },
         stack: {
             raw: verInpt.stack,
diff --git a/setup/lib/setup-haskell.js b/setup/lib/setup-haskell.js
index 0955e598..b9438e14 100644
--- a/setup/lib/setup-haskell.js
+++ b/setup/lib/setup-haskell.js
@@ -79,7 +79,7 @@ async function run(inputs) {
                     // https://github.com/haskell/cabal/issues/6823
                     // await exec('cabal user-config update');
                 }
-                if (!opts.stack.enable)
+                if (opts.cabal.update && !opts.stack.enable)
                     await (0, exec_1.exec)('cabal update');
             });
         core.info(`##[add-matcher]${path.join(__dirname, '..', 'matcher.json')}`);
diff --git a/setup/src/opts.ts b/setup/src/opts.ts
index f9b53dfe..c292ed50 100644
--- a/setup/src/opts.ts
+++ b/setup/src/opts.ts
@@ -24,7 +24,7 @@ export interface ProgramOpt {
 
 export interface Options {
   ghc: ProgramOpt;
-  cabal: ProgramOpt;
+  cabal: ProgramOpt & {update: boolean};
   stack: ProgramOpt & {setup: boolean};
   general: {matcher: {enable: boolean}};
 }
@@ -93,6 +93,7 @@ export function getOpts(
   const stackSetupGhc = (inputs['stack-setup-ghc'] || '') !== '';
   const stackEnable = (inputs['enable-stack'] || '') !== '';
   const matcherDisable = (inputs['disable-matcher'] || '') !== '';
+  const cabalUpdate = inputs['cabal-update'] !== 'false';
   core.debug(`${stackNoGlobal}/${stackSetupGhc}/${stackEnable}`);
   const verInpt = {
     ghc: inputs['ghc-version'] || ghc.version,
@@ -136,7 +137,8 @@ export function getOpts(
         os,
         cabalEnable // if true: inform user about resolution
       ),
-      enable: cabalEnable
+      enable: cabalEnable,
+      update: cabalUpdate
     },
     stack: {
       raw: verInpt.stack,
diff --git a/setup/src/setup-haskell.ts b/setup/src/setup-haskell.ts
index 9e5c5ab3..077c0c6b 100644
--- a/setup/src/setup-haskell.ts
+++ b/setup/src/setup-haskell.ts
@@ -73,7 +73,7 @@ export default async function run(
           // https://github.com/haskell/cabal/issues/6823
           // await exec('cabal user-config update');
         }
-        if (!opts.stack.enable) await exec('cabal update');
+        if (opts.cabal.update && !opts.stack.enable) await exec('cabal update');
       });
 
     core.info(`##[add-matcher]${path.join(__dirname, '..', 'matcher.json')}`);

From 93d09d349bb43c3608cc0f1909d95e8df8c7a10c Mon Sep 17 00:00:00 2001
From: Andreas Abel <andreas.abel@ifi.lmu.de>
Date: Tue, 3 Jan 2023 20:53:29 +0100
Subject: [PATCH 02/10] Test 'cabal-update: false'

---
 .github/workflows/workflow.yml | 1 +
 1 file changed, 1 insertion(+)

diff --git a/.github/workflows/workflow.yml b/.github/workflows/workflow.yml
index 50074e16..2ad85f23 100644
--- a/.github/workflows/workflow.yml
+++ b/.github/workflows/workflow.yml
@@ -72,6 +72,7 @@ jobs:
         with:
           ghc-version: ${{ matrix.ghc }}
           cabal-version: ${{ matrix.cabal }}
+          cabal-update: false
       - name: Test runghc
         run: |
           runghc --version

From e9dab18154a2a2a929a0432aeac7d7ff897222ae Mon Sep 17 00:00:00 2001
From: Andreas Abel <andreas.abel@ifi.lmu.de>
Date: Fri, 6 Jan 2023 02:32:17 +0100
Subject: [PATCH 03/10] README: Add 'cabal-update' to table of inputs

---
 setup/README.md | 21 ++++++++++++---------
 1 file changed, 12 insertions(+), 9 deletions(-)

diff --git a/setup/README.md b/setup/README.md
index 8c08e1ca..49557a85 100644
--- a/setup/README.md
+++ b/setup/README.md
@@ -98,19 +98,22 @@ jobs:
 
 ## Inputs
 
-| Name              | Required | Description                                                                                                                              | Type      | Default     |
-| ----------------- | :------: | ---------------------------------------------------------------------------------------------------------------------------------------- | --------- | ----------- |
-| `ghc-version`     |          | GHC version to use, ex. `latest`                                                                                                         | string    | latest      |
-| `cabal-version`   |          | Cabal version to use, ex. `3.4`                                                                                                          | string    | latest      |
-| `stack-version`   |          | Stack version to use, ex. `latest`. Stack will only be installed if `enable-stack` is set.                                               | string    | latest      |
-| `enable-stack`    |          | If set, will setup Stack.                                                                                                                | "boolean" | false/unset |
-| `stack-no-global` |          | If set, enable-stack must be set. Prevents installing GHC and Cabal globally                                                             | "boolean" | false/unset |
-| `stack-setup-ghc` |          | If set, enable-stack must be set. Runs stack setup to install the specified GHC. (Note: setting this does _not_ imply `stack-no-global`) | "boolean" | false/unset |
-| `disable-matcher` |          | If set, disables match messages from GHC as GitHub CI annotations                                                                        | "boolean" | false/unset |
+| Name              | Description                                                                                                                                 | Type      | Default     |
+| ----------------- | ------------------------------------------------------------------------------------------------------------------------------------------- | --------- | ----------- |
+| `ghc-version`     | GHC version to use, ex. `9.2` or `9.2.4`.                                                                                                   | string    | `latest`    |
+| `cabal-version`   | Cabal version to use, ex. `3.4`.                                                                                                            | string    | `latest`    |
+| `stack-version`   | Stack version to use, ex. `latest`. Stack will only be installed if `enable-stack` is set.                                                  | string    | `latest`    |
+| `enable-stack`    | If set, will setup Stack.                                                                                                                   | "boolean" | false/unset |
+| `stack-no-global` | If set, `enable-stack` must be set. Prevents installing GHC and Cabal globally.                                                             | "boolean" | false/unset |
+| `stack-setup-ghc` | If set, `enable-stack` must be set. Runs stack setup to install the specified GHC. (Note: setting this does _not_ imply `stack-no-global`.) | "boolean" | false/unset |
+| `disable-matcher` | If set, disables match messages from GHC as GitHub CI annotations.                                                                          | "boolean" | false/unset |
+| `cabal-update`    | If set to `false`, skip `cabal update` step.                                                                                                | boolean   | `true`      |
 
 Note: "boolean" types are set/unset, not true/false.
 That is, setting any "boolean" to a value other than the empty string (`""`) will be considered true/set.
 
+In contrast, a proper `boolean` field only accepts values `true` and `false`.
+
 ## Outputs
 
 | Name          | Description                                                                                                                | Type   |

From 9ad367ed9a9a755e8e0e39846989f13ea9e82828 Mon Sep 17 00:00:00 2001
From: Andreas Abel <andreas.abel@ifi.lmu.de>
Date: Fri, 6 Jan 2023 02:34:35 +0100
Subject: [PATCH 04/10] Accept YAML 1.2 booleans as values for 'cabal-update'

---
 setup/dist/index.js | 27 +++++++++++++++++++++++++--
 setup/lib/opts.d.ts | 11 +++++++++++
 setup/lib/opts.js   | 27 +++++++++++++++++++++++++--
 setup/src/opts.ts   | 25 ++++++++++++++++++++++++-
 4 files changed, 85 insertions(+), 5 deletions(-)

diff --git a/setup/dist/index.js b/setup/dist/index.js
index ef10d587..b4983b81 100644
--- a/setup/dist/index.js
+++ b/setup/dist/index.js
@@ -13646,7 +13646,7 @@ var __importStar = (this && this.__importStar) || function (mod) {
     return result;
 };
 Object.defineProperty(exports, "__esModule", ({ value: true }));
-exports.getOpts = exports.releaseRevision = exports.getDefaults = exports.yamlInputs = exports.ghcup_version = exports.supported_versions = exports.release_revisions = void 0;
+exports.getOpts = exports.parseYAMLBoolean = exports.releaseRevision = exports.getDefaults = exports.yamlInputs = exports.ghcup_version = exports.supported_versions = exports.release_revisions = void 0;
 const core = __importStar(__nccwpck_require__(2186));
 const fs_1 = __nccwpck_require__(7147);
 const js_yaml_1 = __nccwpck_require__(1917);
@@ -13692,13 +13692,36 @@ function releaseRevision(version, tool, os) {
     return result;
 }
 exports.releaseRevision = releaseRevision;
+/**
+ * Convert a string input to a boolean according to the YAML 1.2 "core schema" specification.
+ * Supported boolean renderings: `true | True | TRUE | false | False | FALSE` .
+ * ref: https://yaml.org/spec/1.2/spec.html#id2804923
+ * Adapted from: https://github.com/actions/toolkit/commit/fbdf27470cdcb52f16755d32082f1fee0bfb7d6d#diff-f63fb32fca85d8e177d6400ce078818a4815b80ac7a3319b60d3507354890992R94-R115
+ *
+ * @param     name     name of the input
+ * @param     val      supposed string representation of a boolean
+ * @returns   boolean
+ */
+function parseYAMLBoolean(name, val) {
+    const trueValue = ['true', 'True', 'TRUE'];
+    const falseValue = ['false', 'False', 'FALSE'];
+    if (trueValue.includes(val))
+        return true;
+    if (falseValue.includes(val))
+        return false;
+    throw new TypeError(`Action input "${name}" does not meet YAML 1.2 "Core Schema" specification: \n` +
+        `Supported boolean values: \`true | True | TRUE | false | False | FALSE\``);
+}
+exports.parseYAMLBoolean = parseYAMLBoolean;
 function getOpts({ ghc, cabal, stack }, os, inputs) {
     core.debug(`Inputs are: ${JSON.stringify(inputs)}`);
     const stackNoGlobal = (inputs['stack-no-global'] || '') !== '';
     const stackSetupGhc = (inputs['stack-setup-ghc'] || '') !== '';
     const stackEnable = (inputs['enable-stack'] || '') !== '';
     const matcherDisable = (inputs['disable-matcher'] || '') !== '';
-    const cabalUpdate = inputs['cabal-update'] !== 'false';
+    // Andreas, 2023-01-05, issue #29:
+    // 'cabal-update' has a default value, so we should get a proper boolean always. (Fingers crossed.)
+    const cabalUpdate = parseYAMLBoolean('cabal-update', inputs['cabal-update']);
     core.debug(`${stackNoGlobal}/${stackSetupGhc}/${stackEnable}`);
     const verInpt = {
         ghc: inputs['ghc-version'] || ghc.version,
diff --git a/setup/lib/opts.d.ts b/setup/lib/opts.d.ts
index cf66dedb..58ab6542 100644
--- a/setup/lib/opts.d.ts
+++ b/setup/lib/opts.d.ts
@@ -42,5 +42,16 @@ export declare const yamlInputs: Record<string, {
 }>;
 export declare function getDefaults(os: OS): Defaults;
 export declare function releaseRevision(version: string, tool: Tool, os: OS): string;
+/**
+ * Convert a string input to a boolean according to the YAML 1.2 "core schema" specification.
+ * Supported boolean renderings: `true | True | TRUE | false | False | FALSE` .
+ * ref: https://yaml.org/spec/1.2/spec.html#id2804923
+ * Adapted from: https://github.com/actions/toolkit/commit/fbdf27470cdcb52f16755d32082f1fee0bfb7d6d#diff-f63fb32fca85d8e177d6400ce078818a4815b80ac7a3319b60d3507354890992R94-R115
+ *
+ * @param     name     name of the input
+ * @param     val      supposed string representation of a boolean
+ * @returns   boolean
+ */
+export declare function parseYAMLBoolean(name: string, val: string): boolean;
 export declare function getOpts({ ghc, cabal, stack }: Defaults, os: OS, inputs: Record<string, string>): Options;
 export {};
diff --git a/setup/lib/opts.js b/setup/lib/opts.js
index d84b15ff..b4d40af8 100644
--- a/setup/lib/opts.js
+++ b/setup/lib/opts.js
@@ -23,7 +23,7 @@ var __importStar = (this && this.__importStar) || function (mod) {
     return result;
 };
 Object.defineProperty(exports, "__esModule", { value: true });
-exports.getOpts = exports.releaseRevision = exports.getDefaults = exports.yamlInputs = exports.ghcup_version = exports.supported_versions = exports.release_revisions = void 0;
+exports.getOpts = exports.parseYAMLBoolean = exports.releaseRevision = exports.getDefaults = exports.yamlInputs = exports.ghcup_version = exports.supported_versions = exports.release_revisions = void 0;
 const core = __importStar(require("@actions/core"));
 const fs_1 = require("fs");
 const js_yaml_1 = require("js-yaml");
@@ -69,13 +69,36 @@ function releaseRevision(version, tool, os) {
     return result;
 }
 exports.releaseRevision = releaseRevision;
+/**
+ * Convert a string input to a boolean according to the YAML 1.2 "core schema" specification.
+ * Supported boolean renderings: `true | True | TRUE | false | False | FALSE` .
+ * ref: https://yaml.org/spec/1.2/spec.html#id2804923
+ * Adapted from: https://github.com/actions/toolkit/commit/fbdf27470cdcb52f16755d32082f1fee0bfb7d6d#diff-f63fb32fca85d8e177d6400ce078818a4815b80ac7a3319b60d3507354890992R94-R115
+ *
+ * @param     name     name of the input
+ * @param     val      supposed string representation of a boolean
+ * @returns   boolean
+ */
+function parseYAMLBoolean(name, val) {
+    const trueValue = ['true', 'True', 'TRUE'];
+    const falseValue = ['false', 'False', 'FALSE'];
+    if (trueValue.includes(val))
+        return true;
+    if (falseValue.includes(val))
+        return false;
+    throw new TypeError(`Action input "${name}" does not meet YAML 1.2 "Core Schema" specification: \n` +
+        `Supported boolean values: \`true | True | TRUE | false | False | FALSE\``);
+}
+exports.parseYAMLBoolean = parseYAMLBoolean;
 function getOpts({ ghc, cabal, stack }, os, inputs) {
     core.debug(`Inputs are: ${JSON.stringify(inputs)}`);
     const stackNoGlobal = (inputs['stack-no-global'] || '') !== '';
     const stackSetupGhc = (inputs['stack-setup-ghc'] || '') !== '';
     const stackEnable = (inputs['enable-stack'] || '') !== '';
     const matcherDisable = (inputs['disable-matcher'] || '') !== '';
-    const cabalUpdate = inputs['cabal-update'] !== 'false';
+    // Andreas, 2023-01-05, issue #29:
+    // 'cabal-update' has a default value, so we should get a proper boolean always. (Fingers crossed.)
+    const cabalUpdate = parseYAMLBoolean('cabal-update', inputs['cabal-update']);
     core.debug(`${stackNoGlobal}/${stackSetupGhc}/${stackEnable}`);
     const verInpt = {
         ghc: inputs['ghc-version'] || ghc.version,
diff --git a/setup/src/opts.ts b/setup/src/opts.ts
index c292ed50..ed555901 100644
--- a/setup/src/opts.ts
+++ b/setup/src/opts.ts
@@ -83,6 +83,27 @@ export function releaseRevision(version: string, tool: Tool, os: OS): string {
   return result;
 }
 
+/**
+ * Convert a string input to a boolean according to the YAML 1.2 "core schema" specification.
+ * Supported boolean renderings: `true | True | TRUE | false | False | FALSE` .
+ * ref: https://yaml.org/spec/1.2/spec.html#id2804923
+ * Adapted from: https://github.com/actions/toolkit/commit/fbdf27470cdcb52f16755d32082f1fee0bfb7d6d#diff-f63fb32fca85d8e177d6400ce078818a4815b80ac7a3319b60d3507354890992R94-R115
+ *
+ * @param     name     name of the input
+ * @param     val      supposed string representation of a boolean
+ * @returns   boolean
+ */
+export function parseYAMLBoolean(name: string, val: string): boolean {
+  const trueValue = ['true', 'True', 'TRUE'];
+  const falseValue = ['false', 'False', 'FALSE'];
+  if (trueValue.includes(val)) return true;
+  if (falseValue.includes(val)) return false;
+  throw new TypeError(
+    `Action input "${name}" does not meet YAML 1.2 "Core Schema" specification: \n` +
+      `Supported boolean values: \`true | True | TRUE | false | False | FALSE\``
+  );
+}
+
 export function getOpts(
   {ghc, cabal, stack}: Defaults,
   os: OS,
@@ -93,7 +114,9 @@ export function getOpts(
   const stackSetupGhc = (inputs['stack-setup-ghc'] || '') !== '';
   const stackEnable = (inputs['enable-stack'] || '') !== '';
   const matcherDisable = (inputs['disable-matcher'] || '') !== '';
-  const cabalUpdate = inputs['cabal-update'] !== 'false';
+  // Andreas, 2023-01-05, issue #29:
+  // 'cabal-update' has a default value, so we should get a proper boolean always. (Fingers crossed.)
+  const cabalUpdate = parseYAMLBoolean('cabal-update', inputs['cabal-update']);
   core.debug(`${stackNoGlobal}/${stackSetupGhc}/${stackEnable}`);
   const verInpt = {
     ghc: inputs['ghc-version'] || ghc.version,

From 29517550250f7552a4056f8fbfcdc448ca8b3a99 Mon Sep 17 00:00:00 2001
From: Andreas Abel <andreas.abel@ifi.lmu.de>
Date: Fri, 6 Jan 2023 02:52:59 +0100
Subject: [PATCH 05/10] CI: test 'cabal-update: true': project with Hackage
 dependency

---
 .github/workflows/workflow.yml                    | 15 ++++++++++++++-
 .../project-with-hackage-dependency/Main.hs       |  4 ++++
 .../project-with-hackage-dependency/Setup.hs      |  2 ++
 .../project-with-hackage-dependency.cabal         | 11 +++++++++++
 4 files changed, 31 insertions(+), 1 deletion(-)
 create mode 100644 setup/__tests__/project-with-hackage-dependency/Main.hs
 create mode 100644 setup/__tests__/project-with-hackage-dependency/Setup.hs
 create mode 100644 setup/__tests__/project-with-hackage-dependency/project-with-hackage-dependency.cabal

diff --git a/.github/workflows/workflow.yml b/.github/workflows/workflow.yml
index 2ad85f23..e91578e2 100644
--- a/.github/workflows/workflow.yml
+++ b/.github/workflows/workflow.yml
@@ -41,6 +41,8 @@ jobs:
         os: [ubuntu-latest, macOS-latest, windows-latest]
         ghc: ["latest", "8.4.4"]
         cabal: ["latest", "3.2.0.0"]
+        cabal-update: [false]
+        # The following tests do not set 'cabal-update', which defaults to 'true' then.
         include:
           - os: ubuntu-latest
             ghc: "8.2.2"
@@ -68,25 +70,36 @@ jobs:
             cabal: "3.6"
     steps:
       - uses: actions/checkout@v3
+
       - uses: ./setup
         with:
           ghc-version: ${{ matrix.ghc }}
           cabal-version: ${{ matrix.cabal }}
-          cabal-update: false
+          cabal-update: ${{ matrix.cabal-update }}
+
       - name: Test runghc
         run: |
           runghc --version
           runghc __tests__/hello.hs
+
       - name: Build test project
         working-directory: setup/__tests__/project
         run: cabal build
+
       - name: Run test project
         working-directory: setup/__tests__/project
         run: cabal run
+
+      - name: Build and run test with Hackage dependency
+        if:   ${{ matrix.cabal-update != false }}
+        working-directory: setup/__tests__/project-with-hackage-dependency
+        run:  cabal build && cabal run
+
       - name: Show installed versions
         run: |
           cabal --version
           ghc --version
+
       - name: Confirm installed and expected versions match
         shell: bash
         # check that if given in the matrix, the actual version matches:
diff --git a/setup/__tests__/project-with-hackage-dependency/Main.hs b/setup/__tests__/project-with-hackage-dependency/Main.hs
new file mode 100644
index 00000000..29319957
--- /dev/null
+++ b/setup/__tests__/project-with-hackage-dependency/Main.hs
@@ -0,0 +1,4 @@
+module Main where
+
+main :: IO ()
+main = putStrLn "Hello, Hackage!"
diff --git a/setup/__tests__/project-with-hackage-dependency/Setup.hs b/setup/__tests__/project-with-hackage-dependency/Setup.hs
new file mode 100644
index 00000000..9a994af6
--- /dev/null
+++ b/setup/__tests__/project-with-hackage-dependency/Setup.hs
@@ -0,0 +1,2 @@
+import Distribution.Simple
+main = defaultMain
diff --git a/setup/__tests__/project-with-hackage-dependency/project-with-hackage-dependency.cabal b/setup/__tests__/project-with-hackage-dependency/project-with-hackage-dependency.cabal
new file mode 100644
index 00000000..bba60ed4
--- /dev/null
+++ b/setup/__tests__/project-with-hackage-dependency/project-with-hackage-dependency.cabal
@@ -0,0 +1,11 @@
+cabal-version:       >=1.10
+name:                project
+version:             0.1.0.0
+build-type:          Simple
+
+executable project
+  main-is:             Main.hs
+  build-depends:       base
+                       -- Add a package from hackage here to see whether `cabal update` ran.
+                     , base-orphans
+  default-language:    Haskell2010

From 2328dd780ef38ac096d149cd4d6aaef6851c3244 Mon Sep 17 00:00:00 2001
From: Andreas Abel <andreas.abel@ifi.lmu.de>
Date: Fri, 6 Jan 2023 02:59:26 +0100
Subject: [PATCH 06/10] Default value for 'cabal-update'

---
 setup/dist/index.js | 6 ++++--
 setup/lib/opts.js   | 6 ++++--
 setup/src/opts.ts   | 9 +++++++--
 3 files changed, 15 insertions(+), 6 deletions(-)

diff --git a/setup/dist/index.js b/setup/dist/index.js
index b4983b81..898a6cac 100644
--- a/setup/dist/index.js
+++ b/setup/dist/index.js
@@ -13720,8 +13720,10 @@ function getOpts({ ghc, cabal, stack }, os, inputs) {
     const stackEnable = (inputs['enable-stack'] || '') !== '';
     const matcherDisable = (inputs['disable-matcher'] || '') !== '';
     // Andreas, 2023-01-05, issue #29:
-    // 'cabal-update' has a default value, so we should get a proper boolean always. (Fingers crossed.)
-    const cabalUpdate = parseYAMLBoolean('cabal-update', inputs['cabal-update']);
+    // 'cabal-update' has a default value, so we should get a proper boolean always.
+    // Andreas, 2023-01-06: This is not true if we use the action as a library.
+    // Thus, need to patch with default value here.
+    const cabalUpdate = parseYAMLBoolean('cabal-update', inputs['cabal-update'] || 'true');
     core.debug(`${stackNoGlobal}/${stackSetupGhc}/${stackEnable}`);
     const verInpt = {
         ghc: inputs['ghc-version'] || ghc.version,
diff --git a/setup/lib/opts.js b/setup/lib/opts.js
index b4d40af8..7ba2f4d3 100644
--- a/setup/lib/opts.js
+++ b/setup/lib/opts.js
@@ -97,8 +97,10 @@ function getOpts({ ghc, cabal, stack }, os, inputs) {
     const stackEnable = (inputs['enable-stack'] || '') !== '';
     const matcherDisable = (inputs['disable-matcher'] || '') !== '';
     // Andreas, 2023-01-05, issue #29:
-    // 'cabal-update' has a default value, so we should get a proper boolean always. (Fingers crossed.)
-    const cabalUpdate = parseYAMLBoolean('cabal-update', inputs['cabal-update']);
+    // 'cabal-update' has a default value, so we should get a proper boolean always.
+    // Andreas, 2023-01-06: This is not true if we use the action as a library.
+    // Thus, need to patch with default value here.
+    const cabalUpdate = parseYAMLBoolean('cabal-update', inputs['cabal-update'] || 'true');
     core.debug(`${stackNoGlobal}/${stackSetupGhc}/${stackEnable}`);
     const verInpt = {
         ghc: inputs['ghc-version'] || ghc.version,
diff --git a/setup/src/opts.ts b/setup/src/opts.ts
index ed555901..987e037c 100644
--- a/setup/src/opts.ts
+++ b/setup/src/opts.ts
@@ -115,8 +115,13 @@ export function getOpts(
   const stackEnable = (inputs['enable-stack'] || '') !== '';
   const matcherDisable = (inputs['disable-matcher'] || '') !== '';
   // Andreas, 2023-01-05, issue #29:
-  // 'cabal-update' has a default value, so we should get a proper boolean always. (Fingers crossed.)
-  const cabalUpdate = parseYAMLBoolean('cabal-update', inputs['cabal-update']);
+  // 'cabal-update' has a default value, so we should get a proper boolean always.
+  // Andreas, 2023-01-06: This is not true if we use the action as a library.
+  // Thus, need to patch with default value here.
+  const cabalUpdate = parseYAMLBoolean(
+    'cabal-update',
+    inputs['cabal-update'] || 'true'
+  );
   core.debug(`${stackNoGlobal}/${stackSetupGhc}/${stackEnable}`);
   const verInpt = {
     ghc: inputs['ghc-version'] || ghc.version,

From 78df9964cccf50efe25243150cc0d5f79afb11a0 Mon Sep 17 00:00:00 2001
From: Andreas Abel <andreas.abel@ifi.lmu.de>
Date: Fri, 6 Jan 2023 03:10:20 +0100
Subject: [PATCH 07/10] CI: use cabal_update (underscore) in matrix

---
 .github/workflows/workflow.yml | 6 +++---
 1 file changed, 3 insertions(+), 3 deletions(-)

diff --git a/.github/workflows/workflow.yml b/.github/workflows/workflow.yml
index e91578e2..bdfe25d3 100644
--- a/.github/workflows/workflow.yml
+++ b/.github/workflows/workflow.yml
@@ -41,7 +41,7 @@ jobs:
         os: [ubuntu-latest, macOS-latest, windows-latest]
         ghc: ["latest", "8.4.4"]
         cabal: ["latest", "3.2.0.0"]
-        cabal-update: [false]
+        cabal_update: ["false"]
         # The following tests do not set 'cabal-update', which defaults to 'true' then.
         include:
           - os: ubuntu-latest
@@ -75,7 +75,7 @@ jobs:
         with:
           ghc-version: ${{ matrix.ghc }}
           cabal-version: ${{ matrix.cabal }}
-          cabal-update: ${{ matrix.cabal-update }}
+          cabal-update: ${{ matrix.cabal_update }}
 
       - name: Test runghc
         run: |
@@ -91,7 +91,7 @@ jobs:
         run: cabal run
 
       - name: Build and run test with Hackage dependency
-        if:   ${{ matrix.cabal-update != false }}
+        if:   ${{ matrix.cabal_update != 'false' }}
         working-directory: setup/__tests__/project-with-hackage-dependency
         run:  cabal build && cabal run
 

From 1aa5a5cf6734db166bee3444f450e4e35ba72048 Mon Sep 17 00:00:00 2001
From: Andreas Abel <andreas.abel@ifi.lmu.de>
Date: Fri, 6 Jan 2023 03:22:44 +0100
Subject: [PATCH 08/10] Fixup: project with Hackage dependency

---
 .../project-with-hackage-dependency.cabal                       | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/setup/__tests__/project-with-hackage-dependency/project-with-hackage-dependency.cabal b/setup/__tests__/project-with-hackage-dependency/project-with-hackage-dependency.cabal
index bba60ed4..b6e7719b 100644
--- a/setup/__tests__/project-with-hackage-dependency/project-with-hackage-dependency.cabal
+++ b/setup/__tests__/project-with-hackage-dependency/project-with-hackage-dependency.cabal
@@ -1,5 +1,5 @@
 cabal-version:       >=1.10
-name:                project
+name:                project-with-hackage-dependency
 version:             0.1.0.0
 build-type:          Simple
 

From dfd5a5adfbbf1e1653395a57bf65ae761b71decb Mon Sep 17 00:00:00 2001
From: Andreas Abel <andreas.abel@ifi.lmu.de>
Date: Fri, 6 Jan 2023 03:32:14 +0100
Subject: [PATCH 09/10] Work around #158

---
 .github/workflows/workflow.yml | 1 +
 1 file changed, 1 insertion(+)

diff --git a/.github/workflows/workflow.yml b/.github/workflows/workflow.yml
index bdfe25d3..12e98a5b 100644
--- a/.github/workflows/workflow.yml
+++ b/.github/workflows/workflow.yml
@@ -47,6 +47,7 @@ jobs:
           - os: ubuntu-latest
             ghc: "8.2.2"
             cabal: "2.4.1.0"
+            cabal_update: "false"
           - os: ubuntu-18.04
             ghc: "7.4.1"
             cabal: "3.4"

From d3609b3df0873e3de97504c53df3dce2d9c26449 Mon Sep 17 00:00:00 2001
From: Andreas Abel <andreas.abel@ifi.lmu.de>
Date: Tue, 10 Jan 2023 18:22:40 +0100
Subject: [PATCH 10/10] Extra clarification of boolean vs "boolean" inputs

---
 setup/README.md  | 11 ++++++-----
 setup/action.yml |  5 ++++-
 2 files changed, 10 insertions(+), 6 deletions(-)

diff --git a/setup/README.md b/setup/README.md
index 49557a85..db41cd08 100644
--- a/setup/README.md
+++ b/setup/README.md
@@ -100,19 +100,20 @@ jobs:
 
 | Name              | Description                                                                                                                                 | Type      | Default     |
 | ----------------- | ------------------------------------------------------------------------------------------------------------------------------------------- | --------- | ----------- |
-| `ghc-version`     | GHC version to use, ex. `9.2` or `9.2.4`.                                                                                                   | string    | `latest`    |
-| `cabal-version`   | Cabal version to use, ex. `3.4`.                                                                                                            | string    | `latest`    |
-| `stack-version`   | Stack version to use, ex. `latest`. Stack will only be installed if `enable-stack` is set.                                                  | string    | `latest`    |
+| `ghc-version`     | GHC version to use, e.g. `9.2` or `9.2.4`.                                                                                                  | `string`  | `latest`    |
+| `cabal-version`   | Cabal version to use, e.g. `3.4`.                                                                                                           | `string`  | `latest`    |
+| `stack-version`   | Stack version to use, e.g. `latest`. Stack will only be installed if `enable-stack` is set.                                                 | `string`  | `latest`    |
 | `enable-stack`    | If set, will setup Stack.                                                                                                                   | "boolean" | false/unset |
 | `stack-no-global` | If set, `enable-stack` must be set. Prevents installing GHC and Cabal globally.                                                             | "boolean" | false/unset |
 | `stack-setup-ghc` | If set, `enable-stack` must be set. Runs stack setup to install the specified GHC. (Note: setting this does _not_ imply `stack-no-global`.) | "boolean" | false/unset |
 | `disable-matcher` | If set, disables match messages from GHC as GitHub CI annotations.                                                                          | "boolean" | false/unset |
-| `cabal-update`    | If set to `false`, skip `cabal update` step.                                                                                                | boolean   | `true`      |
+| `cabal-update`    | If set to `false`, skip `cabal update` step.                                                                                                | `boolean` | `true`      |
 
 Note: "boolean" types are set/unset, not true/false.
 That is, setting any "boolean" to a value other than the empty string (`""`) will be considered true/set.
+However, to avoid confusion and for forward compatibility, it is still recommended to **only use value `true` to set a "boolean" flag.**
 
-In contrast, a proper `boolean` field only accepts values `true` and `false`.
+In contrast, a proper `boolean` input like `cabal-update` only accepts values `true` and `false`.
 
 ## Outputs
 
diff --git a/setup/action.yml b/setup/action.yml
index 02128abe..bc047ec3 100644
--- a/setup/action.yml
+++ b/setup/action.yml
@@ -26,7 +26,10 @@ inputs:
   cabal-update:
     required: false
     default: true
-    description: 'Set to false to prevent `cabal update` from being run.'
+    description: 'Set to `false` to prevent `cabal update` from being run.'
+    # Note: 'cabal-update' only accepts 'true' and 'false' as values.
+    # This is different from the other flags ('enable-stack', 'disable-matcher' etc.)
+    # which are true as soon as they are not null.
   disable-matcher:
     required: false
     description: 'If specified, disables match messages from GHC as GitHub CI annotations.'