tour: build snippets in module mode

We want to start building snippets in module mode rather than legacy
legacy GOPATH mode, to make tour work well when there's no tour code
in GOPATH/src and to be more future-proof. Building in module mode
means we need to specify a go.mod file to use for each snippet.

The tour web UI design predates the module mode and its go.mod files.
Txtar-based multi-file support was added to the playground (that the
tour uses for executing snippets) in golang.org/issue/32040, but the
web UI hasn't been updated to have first-class separate <textarea>
elements or tabs for editing multiple files.

For now, we can get by with providing a default go.mod file for all
tour snippets, since they only need some packages in the tour module.

Update to a newer version of the golang.org/x/tools/playground/socket
package which includes multi-file snippet support added in CL 204237.

For golang/go#44243.

Change-Id: Ib05725c52fbe43658b2f22ac728b1e901e635824
Reviewed-on: https://go-review.googlesource.com/c/tour/+/291889
Trust: Dmitri Shuralyov <dmitshur@golang.org>
Run-TryBot: Dmitri Shuralyov <dmitshur@golang.org>
TryBot-Result: Go Bot <gobot@golang.org>
Reviewed-by: Russ Cox <rsc@golang.org>

3 files changed, 49 insertions, 5 deletions

diff --git a/go.mod b/go.mod
index 1af74d3..1abb78d 100644
--- a/go.mod
+++ b/go.mod
@@ -2,4 +2,4 @@ module golang.org/x/tour
 
 go 1.11
 
-require golang.org/x/tools v0.0.0-20190312164927-7b79afddac43
+require golang.org/x/tools v0.1.0
diff --git a/go.sum b/go.sum
index 128955b..a4a6c9c 100644
--- a/go.sum
+++ b/go.sum
@@ -1,7 +1,28 @@
+github.com/yuin/goldmark v1.2.1 h1:ruQGxdhGHe7FWOJPT0mKs5+pD2Xs1Bm/kdGlHO04FmM=
+github.com/yuin/goldmark v1.2.1/go.mod h1:3hX8gzYuyVAZsxl0MRgGTJEmQBFcNTphYh9decYSb74=
 golang.org/x/crypto v0.0.0-20190308221718-c2843e01d9a2/go.mod h1:djNgcEr1/C05ACkg1iLfiJU5Ep61QUkGW8qpdssI0+w=
-golang.org/x/net v0.0.0-20190311183353-d8887717615a h1:oWX7TPOiFAMXLq8o0ikBYfCJVlRHBcsciT5bXOrH628=
-golang.org/x/net v0.0.0-20190311183353-d8887717615a/go.mod h1:t9HGtf8HONx5eT2rtn7q6eTqICYqUVnKs3thJo3Qplg=
+golang.org/x/crypto v0.0.0-20191011191535-87dc89f01550/go.mod h1:yigFU9vqHzYiE8UmvKecakEJjdnWj3jj499lnFckfCI=
+golang.org/x/crypto v0.0.0-20200622213623-75b288015ac9/go.mod h1:LzIPMQfyMNhhGPhUkYOs5KpL4U8rLKemX1yGLhDgUto=
+golang.org/x/mod v0.3.0 h1:RM4zey1++hCTbCVQfnWeKs9/IEsaBLA8vTkd0WVtmH4=
+golang.org/x/mod v0.3.0/go.mod h1:s0Qsj1ACt9ePp/hMypM3fl4fZqREWJwdYDEqhRiZZUA=
+golang.org/x/net v0.0.0-20190404232315-eb5bcb51f2a3/go.mod h1:t9HGtf8HONx5eT2rtn7q6eTqICYqUVnKs3thJo3Qplg=
+golang.org/x/net v0.0.0-20190620200207-3b0461eec859/go.mod h1:z5CRVTTTmAJ677TzLLGU+0bjPO0LkuOLi4/5GtJWs/s=
+golang.org/x/net v0.0.0-20201021035429-f5854403a974 h1:IX6qOQeG5uLjB/hjjwjedwfjND0hgjPMMyO1RoIXQNI=
+golang.org/x/net v0.0.0-20201021035429-f5854403a974/go.mod h1:sp8m0HH+o8qH0wwXwYZr8TS3Oi6o0r6Gce1SSxlDquU=
+golang.org/x/sync v0.0.0-20190423024810-112230192c58/go.mod h1:RxMgew5VJxzue5/jJTE5uejpjVlOe/izrB70Jof72aM=
+golang.org/x/sync v0.0.0-20201020160332-67f06af15bc9/go.mod h1:RxMgew5VJxzue5/jJTE5uejpjVlOe/izrB70Jof72aM=
 golang.org/x/sys v0.0.0-20190215142949-d0b11bdaac8a/go.mod h1:STP8DvDyc/dI5b8T5hshtkjS+E42TnysNCUPdjciGhY=
+golang.org/x/sys v0.0.0-20190412213103-97732733099d/go.mod h1:h1NjWce9XRLGQEsW7wpKNCjG9DtNlClVuFLEZdDNbEs=
+golang.org/x/sys v0.0.0-20200930185726-fdedc70b468f/go.mod h1:h1NjWce9XRLGQEsW7wpKNCjG9DtNlClVuFLEZdDNbEs=
+golang.org/x/sys v0.0.0-20210119212857-b64e53b001e4 h1:myAQVi0cGEoqQVR5POX+8RR2mrocKqNN1hmeMqhX27k=
+golang.org/x/sys v0.0.0-20210119212857-b64e53b001e4/go.mod h1:h1NjWce9XRLGQEsW7wpKNCjG9DtNlClVuFLEZdDNbEs=
 golang.org/x/text v0.3.0/go.mod h1:NqM8EUOU14njkJ3fqMW+pc6Ldnwhi/IjpwHt7yyuwOQ=
-golang.org/x/tools v0.0.0-20190312164927-7b79afddac43 h1:TIYuaOnWereVgpmGdM420uV4ykKf3r5m++5s628rZdE=
-golang.org/x/tools v0.0.0-20190312164927-7b79afddac43/go.mod h1:LCzVGOaR6xXOjkQ3onu1FJEFr0SW1gC7cKk1uF8kGRs=
+golang.org/x/text v0.3.3/go.mod h1:5Zoc/QRtKVWzQhOtBMvqHzDpF6irO9z98xDceosuGiQ=
+golang.org/x/tools v0.0.0-20180917221912-90fa682c2a6e/go.mod h1:n7NCudcB/nEzxVGmLbDWY5pfWTLqBcC2KZ6jyYvM4mQ=
+golang.org/x/tools v0.0.0-20191119224855-298f0cb1881e/go.mod h1:b+2E5dAYhXwXZwtnZ6UAqBI28+e2cm9otk0dWdXHAEo=
+golang.org/x/tools v0.1.0 h1:po9/4sTYwZU9lPhi1tOrb4hCv3qrhiQ77LZfGa2OjwY=
+golang.org/x/tools v0.1.0/go.mod h1:xkSsbof2nBLbhDlRMhhhyNLN/zl3eTqcnHD5viDpcZ0=
+golang.org/x/xerrors v0.0.0-20190717185122-a985d3407aa7/go.mod h1:I/5z698sn9Ka8TeJc9MKroUUfqBBauWjQqLJ2OPfmY0=
+golang.org/x/xerrors v0.0.0-20191011141410-1b5146add898/go.mod h1:I/5z698sn9Ka8TeJc9MKroUUfqBBauWjQqLJ2OPfmY0=
+golang.org/x/xerrors v0.0.0-20200804184101-5ec99f83aff1 h1:go1bK/D/BFZV2I8cIQd1NKEZ+0owSTG1fDTci4IqFcE=
+golang.org/x/xerrors v0.0.0-20200804184101-5ec99f83aff1/go.mod h1:I/5z698sn9Ka8TeJc9MKroUUfqBBauWjQqLJ2OPfmY0=
diff --git a/static/js/services.js b/static/js/services.js
index dd4563f..da5f79c 100755
--- a/static/js/services.js
+++ b/static/js/services.js
@@ -49,6 +49,29 @@ factory('run', ['$window', 'editor',
             };
         };
         return function(code, output, options, done) {
+            // We want to build tour snippets in module mode, so append
+            // a default go.mod file when it is not already included in
+            // the txtar archive.
+            //
+            // The exercises use golang.org/x/tour/{pic,reader,tree,wc}
+            // packages, so include the golang.org/x/tour module in the
+            // build list.
+            const hasGoMod = code.indexOf('\n-- go.mod --\n') !== -1 || code.startsWith('-- go.mod --\n');
+            if (!hasGoMod) {
+                code += '\n' +
+                    '-- go.mod --\n' +
+                    'module example\n' +
+                    'require golang.org/x/tour v0.0.0-20201207214521-004403599411\n' +
+                    '-- go.sum --\n' +
+                    'golang.org/x/crypto v0.0.0-20190308221718-c2843e01d9a2/go.mod h1:djNgcEr1/C05ACkg1iLfiJU5Ep61QUkGW8qpdssI0+w=\n' +
+                    'golang.org/x/net v0.0.0-20190311183353-d8887717615a/go.mod h1:t9HGtf8HONx5eT2rtn7q6eTqICYqUVnKs3thJo3Qplg=\n' +
+                    'golang.org/x/sys v0.0.0-20190215142949-d0b11bdaac8a/go.mod h1:STP8DvDyc/dI5b8T5hshtkjS+E42TnysNCUPdjciGhY=\n' +
+                    'golang.org/x/text v0.3.0/go.mod h1:NqM8EUOU14njkJ3fqMW+pc6Ldnwhi/IjpwHt7yyuwOQ=\n' +
+                    'golang.org/x/tools v0.0.0-20190312164927-7b79afddac43/go.mod h1:LCzVGOaR6xXOjkQ3onu1FJEFr0SW1gC7cKk1uF8kGRs=\n' +
+                    'golang.org/x/tour v0.0.0-20201207214521-004403599411 h1:dJ4kVwSGlrLZXW6eo2IOer4Pm3wl2GIG4fytRziMgL8=\n' +
+                    'golang.org/x/tour v0.0.0-20201207214521-004403599411/go.mod h1:qMugOFWX59KzC8Nx7f2uvXxKxAqJfi1J6ZUHAWKnrRA=\n';
+            }
+
             // PlaygroundOutput is defined in playground.js which is prepended
             // to the generated script.js in gotour/tour.go.
             // The next line removes the jshint warning.