Niklas Rosencrantz
Reputation: 26652
Why can I not add a main.rs to a crate's source code and import a struct?
Why can I not clone a git project, add a main.rs and import one of the structs? The compiler complains that the import is unknown and if I make it known it complains about the library file can't be compiled.
My files
C:\Users\datan\proj\gitlab.kitware.com\rust-gitlab>dir
Volume in drive C is OS
Volume Serial Number is 9410-E4E7
Directory of C:\Users\datan\proj\gitlab.kitware.com\rust-gitlab
2019-02-06 02:12 <DIR> .
2019-02-06 02:12 <DIR> ..
2019-02-06 02:04 20 .gitignore
2019-02-06 03:18 <DIR> .idea
2019-02-06 02:05 63 519 Cargo.lock
2019-02-06 02:04 660 Cargo.toml
2019-02-06 02:12 <DIR> cmake-build-debug
2019-02-06 02:04 <DIR> data
2019-02-06 02:04 11 048 LICENSE-APACHE
2019-02-06 02:04 1 082 LICENSE-MIT
2019-02-06 02:04 2 720 README.md
2019-02-06 02:04 335 rustfmt.toml
2019-02-06 03:16 <DIR> src
2019-02-06 02:11 <DIR> target
7 File(s) 79 384 bytes
7 Dir(s) 55 351 238 656 bytes free
My "code":
use types::*;
fn main() {
println!("Hello, rust-gitlab!");
let repo_commit_detail: RepoCommitDetail = read_test_file("repo_commit_detail");
}
Structure
C:\Users\datan\proj\gitlab.kitware.com\rust-gitlab>tree .
Folder PATH listing for volume OS
Volume serial number is 00000242 9410:E4E7
C:\USERS\DATAN\PROJ\GITLAB.KITWARE.COM\RUST-GITLAB
├───.idea
│ └───codeStyles
├───cmake-build-debug
│ └───CMakeFiles
├───data
├───src
│ └───test
└───target
└───debug
├───.fingerprint
│ ├───adler32-008121952d6e723e
│ ├───arrayvec-646ad0ece92a7d00
│ ├───arrayvec-800298e92d8a6b00
│ ├───arrayvec-8dcfe3021b2d6a8c
│ ├───autocfg-d540d3308658af53
│ ├───backtrace-4a5d8bbe58343768
│ ├───backtrace-76389fa126a505ca
│ ├───backtrace-a25120398233fbf2
│ ├───base64-8605715cecafa1de
│ ├───byteorder-6005d7caf2ed9454
│ ├───byteorder-675368122e548ca7
│ ├───byteorder-cacda78970cb326d
│ ├───bytes-245614f42b19aebe
│ ├───cfg-if-199b060bf8390609
│ ├───chrono-5959f27994de03e0
│ ├───crc32fast-0e880f27a0ce35a3
│ ├───crc32fast-601ce62d000e21bd
│ ├───crc32fast-9c59fdb01a618f87
│ ├───crossbeam-424114c559f55459
│ ├───crossbeam-channel-11d639148a522581
│ ├───crossbeam-deque-52c98f99d1a02bdd
│ ├───crossbeam-epoch-af8d62f026998a89
│ ├───crossbeam-utils-0d1e4d7da8a9ef57
│ ├───dtoa-24ecc23d181a18d5
│ ├───either-2ee3e437ff6c971e
│ ├───encoding_rs-d0dc5ad1a07eed3c
│ ├───encoding_rs-da47aa074a980d52
│ ├───encoding_rs-fd6e16943622578f
│ ├───error-chain-bf90b77261c62193
│ ├───fnv-aa2431fc6bc1ad66
│ ├───futures-c6e67b10dc6edbd6
│ ├───futures-cpupool-8e39e86f34ba679d
│ ├───gitlab-08ffdd36690d90f8
│ ├───gitlab-11fbba92a7cac036
│ ├───gitlab-6a33ea7f6205065e
│ ├───gitlab-ff4e8c6912a1992b
│ ├───h2-0ee18ce773a0a89d
│ ├───http-d2636b675bcf6465
│ ├───httparse-3bfb6bbc4103b725
│ ├───httparse-945236f44bbaae4b
│ ├───httparse-a633d1291de4b063
│ ├───hyper-d5c769dc0bac17de
│ ├───hyper-tls-bb5d862976202e56
│ ├───idna-eb455bf3c0c933b1
│ ├───indexmap-fd3d2119afdeaa48
│ ├───iovec-baee453073a2d5a5
│ ├───itertools-ecd8c4d65670cbd4
│ ├───itoa-2d8a8a209336a4b1
│ ├───kernel32-sys-323344e9ba717bff
│ ├───kernel32-sys-83eb403a9b94134f
│ ├───kernel32-sys-8f6a7cb898839565
│ ├───lazycell-c863022fb753ec04
│ ├───lazy_static-ba3bb80e02027d7a
│ ├───libc-058cf61bc83378d2
│ ├───libc-0d6d3d189a8fcbc8
│ ├───libc-7939fbb070556365
│ ├───libflate-dda03a69fd4704db
│ ├───lock_api-effbd268c74fb367
│ ├───log-2694fa5b5ff478b9
│ ├───matches-34ff768fe7fdff16
│ ├───memoffset-5218595f33c3708e
│ ├───mime-c20b452517077c0f
│ ├───mime_guess-78f6fdcc75bfb801
│ ├───mime_guess-b0cdb33e00444552
│ ├───mime_guess-bbd685b703852b01
│ ├───mio-97ff8160514f5116
│ ├───miow-77aa8c8f9462ad96
│ ├───native-tls-3753990a7317fe2a
│ ├───native-tls-6abda051a7bbee28
│ ├───native-tls-f608c79f4e18dacd
│ ├───net2-508ac492f9b7b00d
│ ├───nodrop-9f556cbcc9819baa
│ ├───num-integer-3b8af9e09499eb17
│ ├───num-integer-6591db06d92151f8
│ ├───num-integer-f5b2b5fbdf9ab12f
│ ├───num-traits-122ab06899abc72a
│ ├───num-traits-5e3121b94e205820
│ ├───num-traits-892c39b3d2eb30ab
│ ├───num_cpus-e0b2ff8b8d59c6e1
│ ├───owning_ref-bf183c7d773e0123
│ ├───parking_lot-12a126bd707a9322
│ ├───parking_lot_core-5118c128aa288759
│ ├───parking_lot_core-d807a50d17f4c651
│ ├───parking_lot_core-ff708f491c5bff4c
│ ├───percent-encoding-2476bdc6c1b57ab9
│ ├───phf-94566d3a79ef4ee4
│ ├───phf_codegen-e81124e1842629f7
│ ├───phf_generator-77be707e85bdbaab
│ ├───phf_shared-83f1cdc4827f16e2
│ ├───proc-macro2-3730dc9da7871eda
│ ├───proc-macro2-490294cd99fdab5c
│ ├───proc-macro2-a7ad7b68ac88e1e9
│ ├───quote-0815e85bf26aa999
│ ├───rand-36058bce56ceb9f0
│ ├───rand-7bb4cfe73bf0dd1e
│ ├───rand-e1919e05ce4b78ef
│ ├───rand_chacha-5b135890bc288e05
│ ├───rand_chacha-88fea0759acfb849
│ ├───rand_chacha-ff6617e45043fb8d
│ ├───rand_core-22f8b569c1c44c74
│ ├───rand_core-44b0efb2e9232e43
│ ├───rand_hc-6db16b100e560df6
│ ├───rand_isaac-cd4ed7aeaa173fa8
│ ├───rand_jitter-594b9541efdf7198
│ ├───rand_os-408f5a001096e49e
│ ├───rand_pcg-04b94dbba308ed6e
│ ├───rand_pcg-7251ce262f199c3c
│ ├───rand_pcg-ee7758f0896a3792
│ ├───rand_xorshift-b4798ffeed80dc8e
│ ├───reqwest-8cc9d5a46fc1cada
│ ├───rustc-demangle-54becd0a270f9042
│ ├───rustc_version-a903e7df435c73ab
│ ├───ryu-5f4d3c0db59c3c54
│ ├───ryu-6ba019180c4a274b
│ ├───ryu-9235d9421bf627c7
│ ├───schannel-8bdf6ec01769ef1c
│ ├───scopeguard-56bbc3bacf26b561
│ ├───semver-c5c93388824cc96e
│ ├───semver-parser-654d61a88b761106
│ ├───serde-d8d5485694af815f
│ ├───serde-dad6256f5839031b
│ ├───serde-fe431a9eda84f305
│ ├───serde_derive-27a8dc8a7e741ec3
│ ├───serde_json-54e6f40131bbe4f3
│ ├───serde_urlencoded-164f04fa4cf91ece
│ ├───siphasher-2144e89659a7ccab
│ ├───slab-29ad5a838c81f6af
│ ├───smallvec-8c0ee41d14e5bd2a
│ ├───stable_deref_trait-6b5901538f6cb51d
│ ├───string-726f5a2abd463420
│ ├───syn-3788b283d77da292
│ ├───time-2cbb174b24b625e6
│ ├───tokio-current-thread-3f718ab37342974a
│ ├───tokio-executor-e90e6a555413eaff
│ ├───tokio-f4f06f03abb9066d
│ ├───tokio-io-83563994d5ed4ae3
│ ├───tokio-reactor-cee5f1c0b2993ee0
│ ├───tokio-tcp-e384fdc1139f59d4
│ ├───tokio-threadpool-f5fc7c392f4d3bcd
│ ├───tokio-timer-baf35f3876a94a68
│ ├───try-lock-5b05e80f1baf5381
│ ├───unicase-24a369037c028ed4
│ ├───unicase-355ca4fd327fabfd
│ ├───unicase-5ce264aa1273838b
│ ├───unicase-8ac0f082768d424a
│ ├───unicase-cf024d918a538866
│ ├───unicase-e9044cba12acdee6
│ ├───unicode-bidi-bb475f0c3944d6b7
│ ├───unicode-normalization-64e9089438d2ebfd
│ ├───unicode-xid-a7467f62a39abf94
│ ├───unreachable-67223564bef6342d
│ ├───url-58e1116538252022
│ ├───uuid-8d3ab2c31242ff75
│ ├───version_check-8ad7f975e23d024d
│ ├───void-0896fe1d47015a04
│ ├───want-6f48436d34182abd
│ ├───winapi-4a53e903331f64f4
│ ├───winapi-4b6d1267534d970d
│ ├───winapi-6f75c5e1021b74d7
│ ├───winapi-752db0e8208ff517
│ ├───winapi-build-2ed6cec7c9de885d
│ ├───ws2_32-sys-5c26f11f3d3ba52f
│ ├───ws2_32-sys-a6c2fe9a71ea1454
│ └───ws2_32-sys-e4a5aabbb21dd0b8
├───build
│ ├───arrayvec-646ad0ece92a7d00
│ │ └───out
│ ├───arrayvec-8dcfe3021b2d6a8c
│ ├───backtrace-4a5d8bbe58343768
│ │ └───out
│ ├───backtrace-76389fa126a505ca
│ ├───byteorder-6005d7caf2ed9454
│ ├───byteorder-cacda78970cb326d
│ │ └───out
│ ├───crc32fast-601ce62d000e21bd
│ │ └───out
│ ├───crc32fast-9c59fdb01a618f87
│ ├───encoding_rs-d0dc5ad1a07eed3c
│ ├───encoding_rs-da47aa074a980d52
│ │ └───out
│ ├───httparse-3bfb6bbc4103b725
│ ├───httparse-a633d1291de4b063
│ │ └───out
│ ├───kernel32-sys-323344e9ba717bff
│ │ └───out
│ ├───kernel32-sys-83eb403a9b94134f
│ ├───libc-058cf61bc83378d2
│ ├───libc-7939fbb070556365
│ │ └───out
│ ├───mime_guess-78f6fdcc75bfb801
│ ├───mime_guess-b0cdb33e00444552
│ │ └───out
│ ├───native-tls-6abda051a7bbee28
│ ├───native-tls-f608c79f4e18dacd
│ │ └───out
│ ├───num-integer-3b8af9e09499eb17
│ │ └───out
│ ├───num-integer-f5b2b5fbdf9ab12f
│ ├───num-traits-122ab06899abc72a
│ ├───num-traits-892c39b3d2eb30ab
│ │ └───out
│ ├───parking_lot_core-5118c128aa288759
│ ├───parking_lot_core-ff708f491c5bff4c
│ │ └───out
│ ├───proc-macro2-3730dc9da7871eda
│ │ └───out
│ ├───proc-macro2-a7ad7b68ac88e1e9
│ ├───rand-7bb4cfe73bf0dd1e
│ ├───rand-e1919e05ce4b78ef
│ │ └───out
│ ├───rand_chacha-5b135890bc288e05
│ │ └───out
│ ├───rand_chacha-88fea0759acfb849
│ ├───rand_pcg-04b94dbba308ed6e
│ │ └───out
│ ├───rand_pcg-ee7758f0896a3792
│ ├───ryu-5f4d3c0db59c3c54
│ │ └───out
│ ├───ryu-6ba019180c4a274b
│ ├───serde-d8d5485694af815f
│ ├───serde-fe431a9eda84f305
│ │ └───out
│ ├───unicase-355ca4fd327fabfd
│ │ └───out
│ ├───unicase-5ce264aa1273838b
│ ├───unicase-8ac0f082768d424a
│ │ └───out
│ ├───unicase-e9044cba12acdee6
│ ├───winapi-6f75c5e1021b74d7
│ │ └───out
│ ├───winapi-752db0e8208ff517
│ ├───ws2_32-sys-a6c2fe9a71ea1454
│ │ └───out
│ └───ws2_32-sys-e4a5aabbb21dd0b8
├───deps
├───examples
├───incremental
│ ├───gitlab-18ycyqu9smunr
│ │ └───s-f97zmznulc-1et4slk-glq89ki51e1z
│ ├───gitlab-2ig8akjm0w1yx
│ │ ├───s-f980cgaxw0-1jrgkvo-1ievukzcrjc88
│ │ └───s-f981eiai94-z9lt25-working
│ └───gitlab-3fwelxjyajmph
│ └───s-f97zp4swxe-tfxev5-1duuud7rw47m5
└───native
If I make my main.rs compile by following all available advice, then I break the library which I have not touched:
error[E0433]: failed to resolve: maybe a missing extern crate crates;? --> src\types.rs:17:5 | 17 | use crates::chrono::{DateTime, NaiveDate, Utc}; | ^^^^^^ maybe a missing extern crate crates;?
Upvotes: 0
Views: 346
Answers (1)
Shepmaster
Reputation: 430506
First things first, go back and re-read The Rust Programming Language's chapter on "Packages, Crates, and Modules". This discusses several fundamental concepts that are vital for understanding.
Why can I not clone a git project, add a main.rs and import one of the structs?
To me, this feels like the same question as "why can't I reach into another human, grab their lungs, and then use them to breathe"? You simply cannot download some arbitrary Rust library and start pulling random files out of it and expect them to work.
Specifically in your case, all libraries have a lib.rs that is the crate root. The crate root tends to have many common definitions that are needed by the rest of the code and imports all the submodules. When you create a main.rs and declare the modules from the library as your own, your main.rs becomes the crate root, but it doesn't define all the things that the library needs. This causes the code to fail to compile.
Instead, just use the crate as a library, as it's intended.
The easiest thing to do create a new Cargo project and add the crate as a dependency to your Cargo.toml. The gitlab crate is already distributed on crates.io, so you just add the version number:
[dependencies]
gitlab = "0.1104.1"
Add use gitlab::types::* in your main.rs and write your code.
If you need to use the locally-checked out sources (perhaps you are modifying the crate?), or if you really want to edit the upstream library to have both a lib.rs and main.rs, see:
Upvotes: 4
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